Stockfish 1.6.1

Workaround a gcc optimization bug.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

Readme.txt

@@ -1,91 +1,90 @@
-1. Introduction
----------------
-
-Stockfish is a free UCI chess engine derived from Glaurung 2.1. It is
-not a complete chess program, but requires some UCI compatible GUI
-(like XBoard with PolyGlot, eboard, Jos<6F>, Arena, Sigma Chess, Shredder,
-Chess Partner, or Fritz) in order to be used comfortably.  Read the
-documentation for your GUI of choice for information about how to use
-Stockfish with your GUI.
-
-This version of Stockfish supports up to 8 CPUs, but has not been
-tested thoroughly with more than 2.  The program tries to detect the
-number of CPUs on your computer and set the number of search threads
-accordingly, but please be aware that the detection is not always
-correct.  It is therefore recommended to inspect the value of the
-"Threads" UCI parameter, and to make sure it equals the number of CPU
+1. Introduction
+---------------
+
+Stockfish is a free UCI chess engine derived from Glaurung 2.1. It is
+not a complete chess program, but requires some UCI compatible GUI
+(like XBoard with PolyGlot, eboard, Jos<6F>, Arena, Sigma Chess, Shredder,
+Chess Partner, or Fritz) in order to be used comfortably.  Read the
+documentation for your GUI of choice for information about how to use
+Stockfish with your GUI.
+
+This version of Stockfish supports up to 8 CPUs, but has not been
+tested thoroughly with more than 2.  The program tries to detect the
+number of CPUs on your computer and set the number of search threads
+accordingly, but please be aware that the detection is not always
+correct.  It is therefore recommended to inspect the value of the
+"Threads" UCI parameter, and to make sure it equals the number of CPU
 cores on your computer. If you are using more than four threads, it
 is recommended to raise the value of "Minimum Split Depth" UCI parameter
 to 6.
-
-
-2. Files
---------
-
-This distribution of Stockfish consists of the following files:
-
-  * Readme.txt, the file you are currently reading.
-
-  * Copying.txt, a text file containing the GNU General Public
-    License.
-
-  * src/, a subdirectory containing the full source code, including a
-    Makefile that can be used to compile Stockfish on Unix-like
-    systems.  For further information about how to compile Stockfish
-    yourself, read section 4 below.
-
-  * polyglot.ini, for using Stockfish with Fabien Letouzey's PolyGlot
-    adapter.
-
-
-3. Opening books
-----------------
-
-This version of Stockfish has experimental support for PolyGlot opening
-books. For information about how to create such books, consult the
-PolyGlot documentation.  The book file can be selected by setting the
-UCI parameter "Book File".
-
-
-4. Compiling it yourself
-------------------------
-
-On Unix-like systems, it should usually be possible to compile
-Stockfish directly from the source code with the included Makefile.
-The exception is computer with big-endian CPUs, like PowerPC
-Macintoshes. Some of the bitboard routines in the current version of
-Stockfish are endianness-sensitive, and won't work on a big-endian CPU.
-
-Stockfish has POPCNT instruction runtime detection and support. This can
-give an extra speed on Core i7 or similar systems. To enable this feature
-(disabled by default) simply uncomment #define USE_POPCNT in bitcount.h
-before to compile.
-
-On 64 bit Unix-like systems the 'bsfq' assembly instruction will be used
-for bit counting. Detection is automatic at compile time, but in case you
-experience compile problems you can comment out #define USE_BSFQ line in types.h
-
-
-5. Terms of use
----------------
-
-Stockfish is free, and distributed under the GNU General Public License
-(GPL).  Essentially, this means that you are free to do almost exactly
-what you want with the program, including distributing it among your
-friends, making it available for download from your web site, selling
-it (either by itself or as part of some bigger software package), or
-using it as the starting point for a software project of your own.
-
-The only real limitation is that whenever you distribute Stockfish in
-some way, you must always include the full source code, or a pointer
-to where the source code can be found.  If you make any changes to the
-source code, these changes must also be made available under the GPL.
-
-For full details, read the copy of the GPL found in the file named
-Copying.txt.
-
-
-6. Feedback
------------
-
-The author's e-mail address is mcostalba@gmail.com
+
+
+2. Files
+--------
+
+This distribution of Stockfish consists of the following files:
+
+  * Readme.txt, the file you are currently reading.
+
+  * Copying.txt, a text file containing the GNU General Public
+    License.
+
+  * src/, a subdirectory containing the full source code, including a
+    Makefile that can be used to compile Stockfish on Unix-like
+    systems.  For further information about how to compile Stockfish
+    yourself, read section 4 below.
+
+  * polyglot.ini, for using Stockfish with Fabien Letouzey's PolyGlot
+    adapter.
+
+
+3. Opening books
+----------------
+
+This version of Stockfish has experimental support for PolyGlot opening
+books. For information about how to create such books, consult the
+PolyGlot documentation.  The book file can be selected by setting the
+UCI parameter "Book File".
+
+
+4. Compiling it yourself
+------------------------
+
+On Unix-like systems, it should usually be possible to compile
+Stockfish directly from the source code with the included Makefile.
+
+For big-endian machines like Power PC you need to enable the proper
+flag changing from -DNBIGENDIAN to -DBIGENDIAN in the Makefile.
+
+Stockfish has POPCNT instruction runtime detection and support. This can
+give an extra speed on Core i7 or similar systems. To enable this feature
+compile with 'make icc-profile-popcnt'
+
+On 64 bit Unix-like systems the 'bsfq' assembly instruction will be used
+for bit counting. Detection is automatic at compile time, but in case you
+experience compile problems you can comment out #define USE_BSFQ line in types.h
+
+
+5. Terms of use
+---------------
+
+Stockfish is free, and distributed under the GNU General Public License
+(GPL).  Essentially, this means that you are free to do almost exactly
+what you want with the program, including distributing it among your
+friends, making it available for download from your web site, selling
+it (either by itself or as part of some bigger software package), or
+using it as the starting point for a software project of your own.
+
+The only real limitation is that whenever you distribute Stockfish in
+some way, you must always include the full source code, or a pointer
+to where the source code can be found.  If you make any changes to the
+source code, these changes must also be made available under the GPL.
+
+For full details, read the copy of the GPL found in the file named
+Copying.txt.
+
+
+6. Feedback
+-----------
+
+The author's e-mail address is mcostalba@gmail.com

src/Makefile

@@ -25,8 +25,11 @@ EXE = stockfish
 ### ==========================================================================
 ### Compiler speed switches for both GCC and ICC. These settings are generally
 ### fast on a broad range of systems, but may be changed experimentally
+###
+### NOTE: Some versions of gcc miscompile value.h with -O2 or -O3, this is the
+### safe setup, try changing to -O3 or -O2 and verify it works for you.
 ### ==========================================================================
-GCCFLAGS = -O3 -msse
+GCCFLAGS = -O1 -msse
 ICCFLAGS = -fast -msse
 ICCFLAGS-OSX = -fast -mdynamic-no-pic
 
@@ -39,6 +42,14 @@ ICCFLAGS += -DNDEBUG
 ICCFLAGS-OSX += -DNDEBUG
 
 
+### ==========================================================================
+### Remove below comments to compile for a big-endian machine
+### ==========================================================================
+#GCCFLAGS += -DBIGENDIAN
+#ICCFLAGS += -DBIGENDIAN
+#ICCFLAGS-OSX += -DBIGENDIAN
+
+
 ### ==========================================================================
 ### Run built-in benchmark for pgo-builds with:  32MB hash  1 thread  10 depth
 ### These settings are generally fast, but may be changed experimentally
@@ -47,9 +58,9 @@ PGOBENCH = ./$(EXE) bench 32 1 10 default depth
 
 
 ### General compiler settings. Do not change
-GCCFLAGS += -g -Wall -fno-exceptions -fno-rtti -fno-strict-aliasing
-ICCFLAGS += -g -Wall -fno-exceptions -fno-rtti -fno-strict-aliasing -wd383,869,981,10187,10188,11505,11503
-ICCFLAGS-OSX += -g -Wall -fno-exceptions -fno-rtti -fno-strict-aliasing -wd383,869,981,10187,10188,11505,11503
+GCCFLAGS += -g -Wall -fno-exceptions -fno-rtti
+ICCFLAGS += -g -Wall -fno-exceptions -fno-rtti -wd383,869,981,10187,10188,11505,11503
+ICCFLAGS-OSX += -g -Wall -fno-exceptions -fno-rtti -wd383,869,981,10187,10188,11505,11503
 
 
 ### General linker settings. Do not change
@@ -74,6 +85,7 @@ help:
 	@echo "make                >  Default: Compiler = g++"
 	@echo "make icc            >  Compiler = icpc"
 	@echo "make icc-profile    >  Compiler = icpc + automatic pgo-build"
+	@echo "make icc-profile-popcnt >  Compiler = icpc + automatic pgo-build + popcnt-support"
 	@echo "make osx-ppc32      >  PPC-Mac OS X 32 bit. Compiler = g++"
 	@echo "make osx-ppc64      >  PPC-Mac OS X 64 bit. Compiler = g++"
 	@echo "make osx-x86        >  x86-Mac OS X 32 bit. Compiler = g++"
@@ -133,6 +145,40 @@ icc-profile:
 	$(MAKE) icc-profile-use
 	@rm -rf profdir bench.txt
 
+icc-profile-make-with-popcnt:
+	$(MAKE) \
+	CXX='icpc' \
+	CXXFLAGS="$(ICCFLAGS) -DUSE_POPCNT" \
+	CXXFLAGS+='-prof-gen=srcpos -prof_dir ./profdir' \
+	all
+
+icc-profile-use-with-popcnt:
+	$(MAKE) \
+	CXX='icpc' \
+	CXXFLAGS="$(ICCFLAGS) -DUSE_POPCNT" \
+	CXXFLAGS+='-prof_use -prof_dir ./profdir' \
+	all
+
+icc-profile-popcnt:
+	@rm -rf profdir
+	@mkdir profdir
+	@touch *.cpp *.h
+	$(MAKE) icc-profile-make
+	@echo ""
+	@echo "Running benchmark for pgo-build (popcnt disabled)..."
+	@$(PGOBENCH) > /dev/null
+	@touch *.cpp *.h
+	$(MAKE) icc-profile-make-with-popcnt
+	@echo ""
+	@echo "Running benchmark for pgo-build (popcnt enabled)..."
+	@$(PGOBENCH) > /dev/null
+	@echo "Benchmarks finished. Build final executable now ..."
+	@echo ""
+	@touch *.cpp *.h
+	$(MAKE) icc-profile-use-with-popcnt
+	@rm -rf profdir bench.txt
+
+
 osx-ppc32:
 	$(MAKE) \
 	CXX='g++' \

src/benchmark.cpp

@@ -104,7 +104,7 @@ void benchmark(const string& commandLine) {
 
   if (limitType == "time")
       secsPerPos = val * 1000;
-  else if (limitType == "depth")
+  else if (limitType == "depth" || limitType == "perft")
       maxDepth = val;
   else
       maxNodes = val;
@@ -153,7 +153,9 @@ void benchmark(const string& commandLine) {
       int dummy[2] = {0, 0};
       Position pos(*it);
       cerr << "\nBench position: " << cnt << '/' << positions.size() << endl << endl;
-      if (!think(pos, true, false, 0, dummy, dummy, 0, maxDepth, maxNodes, secsPerPos, moves))
+      if (limitType == "perft")
+          totalNodes += perft(pos, maxDepth * OnePly);
+      else if (!think(pos, true, false, 0, dummy, dummy, 0, maxDepth, maxNodes, secsPerPos, moves))
           break;
       totalNodes += nodes_searched();
   }

src/bitboard.cpp

@@ -317,8 +317,8 @@ Square pop_1st_bit(Bitboard* b) {
 
 #elif !defined(USE_BSFQ)
 
-CACHE_LINE_ALIGNMENT
-static const int BitTable[64] = {
+static CACHE_LINE_ALIGNMENT
+const int BitTable[64] = {
   63, 30, 3, 32, 25, 41, 22, 33, 15, 50, 42, 13, 11, 53, 19, 34, 61, 29, 2,
   51, 21, 43, 45, 10, 18, 47, 1, 54, 9, 57, 0, 35, 62, 31, 40, 4, 49, 5, 52,
   26, 60, 6, 23, 44, 46, 27, 56, 16, 7, 39, 48, 24, 59, 14, 12, 55, 38, 28,
@@ -336,30 +336,59 @@ union b_union {
 
     Bitboard b;
     struct {
+#if defined (BIGENDIAN)
+        uint32_t h;
+        uint32_t l;
+#else
         uint32_t l;
         uint32_t h;
+#endif
     } dw;
 };
 
-// WARNING: Needs -fno-strict-aliasing compiler option
 Square pop_1st_bit(Bitboard* bb) {
 
-  b_union u;
+   b_union* u;
+   Square ret;
 
-  u.b = *bb;
+   u = (b_union*)bb;
 
-  if (u.dw.l)
-  {
-      *((uint32_t*)bb) = u.dw.l & (u.dw.l - 1);
-      return Square(BitTable[((u.dw.l ^ (u.dw.l - 1)) * 0x783a9b23) >> 26]);
-  }
-
-  *((uint32_t*)bb+1) = u.dw.h & (u.dw.h - 1); // Little endian only?
-  return Square(BitTable[((~(u.dw.h ^ (u.dw.h - 1))) * 0x783a9b23) >> 26]);
+   if (u->dw.l)
+   {
+       ret = Square(BitTable[((u->dw.l ^ (u->dw.l - 1)) * 0x783a9b23) >> 26]);
+       u->dw.l &= (u->dw.l - 1);
+       return ret;
+   }
+   ret = Square(BitTable[((~(u->dw.h ^ (u->dw.h - 1))) * 0x783a9b23) >> 26]);
+   u->dw.h &= (u->dw.h - 1);
+   return ret;
 }
 
 #endif
 
+int bitScanReverse32(uint32_t b)
+{
+   int result = 0;
+
+   if (b > 0xFFFF) {
+      b >>= 16;
+      result += 16;
+   }
+   if (b > 0xFF) {
+      b >>= 8;
+      result += 8;
+   }
+   if (b > 0xF) {
+      b >>= 4;
+      result += 4;
+   }
+   if (b > 0x3) {
+      b >>= 2;
+      result += 2;
+   }
+   return result + (b > 0) + (b > 1);
+}
+
 namespace {
 
   // All functions below are used to precompute various bitboards during

src/bitboard.h

@@ -349,6 +349,7 @@ extern Square pop_1st_bit(Bitboard* b);
 
 extern void print_bitboard(Bitboard b);
 extern void init_bitboards();
+extern int bitScanReverse32(uint32_t b);
 
 
 #endif // !defined(BITBOARD_H_INCLUDED)

src/bitcount.h

@@ -22,19 +22,12 @@
 #if !defined(BITCOUNT_H_INCLUDED)
 #define BITCOUNT_H_INCLUDED
 
-// To enable POPCNT support uncomment USE_POPCNT define. For PGO compile on a Core i7
-// you may want to collect profile data first with USE_POPCNT disabled and then, in a
-// second profiling session, with USE_POPCNT enabled so to exercise both paths. Don't
-// forget to leave USE_POPCNT enabled for the final optimized compile though ;-)
-
-//#define USE_POPCNT
-
-
 #include "types.h"
 
-// Select type of intrinsic bit count instruction to use
+// Select type of intrinsic bit count instruction to use, see
+// README.txt on how to pgo compile with POPCNT support.
 
-#if defined(__INTEL_COMPILER) && defined(IS_64BIT) && defined(USE_POPCNT) // Intel compiler
+#if defined(__INTEL_COMPILER) && defined(USE_POPCNT) // Intel compiler
 
 #include <nmmintrin.h>
 
@@ -45,17 +38,9 @@ inline bool cpu_has_popcnt() {
   return (CPUInfo[2] >> 23) & 1;
 }
 
-// Define a dummy template to workaround a compile error if _mm_popcnt_u64() is not defined.
-//
-// If _mm_popcnt_u64() is defined in <nmmintrin.h> it will be choosen first due to
-// C++ overload rules that always prefer a function to a template with the same name.
-// If not, we avoid a compile error and because cpu_has_popcnt() should return false,
-// our templetized _mm_popcnt_u64() is never called anyway.
-template<typename T> inline unsigned _mm_popcnt_u64(T) { return 0; } // Is never called
-
 #define POPCNT_INTRINSIC(x) _mm_popcnt_u64(x)
 
-#elif defined(_MSC_VER) && defined(IS_64BIT) && defined(USE_POPCNT) // Microsoft compiler
+#elif defined(_MSC_VER) && defined(USE_POPCNT) // Microsoft compiler
 
 #include <intrin.h>
 
@@ -66,9 +51,6 @@ inline bool cpu_has_popcnt() {
   return (CPUInfo[2] >> 23) & 1;
 }
 
-// See comment of _mm_popcnt_u64<>() few lines above for an explanation.
-template<typename T> inline unsigned __popcnt64(T) { return 0; } // Is never called
-
 #define POPCNT_INTRINSIC(x) __popcnt64(x)
 
 #else // Safe fallback for unsupported compilers or when USE_POPCNT is disabled

src/evaluate.h

@@ -25,6 +25,8 @@
 //// Includes
 ////
 
+#include <iostream>
+
 #include "material.h"
 #include "pawns.h"
 
@@ -46,7 +48,7 @@ class Position;
 struct EvalInfo {
 
   // Middle game and endgame evaluations
-  Value mgValue, egValue;
+  Score value;
 
   // Pointers to material and pawn hash table entries
   MaterialInfo* mi;
@@ -89,7 +91,7 @@ struct EvalInfo {
   Move mateThreat[2];
 
   // Middle game and endgame mobility scores.
-  Value mgMobility, egMobility;
+  Score mobility;
 
   // Extra futility margin. This is added to the standard futility margin
   // in the quiescence search.

src/history.cpp

@@ -42,8 +42,6 @@ History::History() { clear(); }
 
 void History::clear() {
   memset(history, 0, 2 * 8 * 64 * sizeof(int));
-  memset(successCount, 0, 2 * 8 * 64 * sizeof(int));
-  memset(failureCount, 0, 2 * 8 * 64 * sizeof(int));
 }
 
 
@@ -58,7 +56,6 @@ void History::success(Piece p, Square to, Depth d) {
   assert(square_is_ok(to));
 
   history[p][to] += int(d) * int(d);
-  successCount[p][to]++;
 
   // Prevent history overflow
   if (history[p][to] >= HistoryMax)
@@ -72,12 +69,14 @@ void History::success(Piece p, Square to, Depth d) {
 /// called for each non-capturing move which failed to produce a beta cutoff
 /// at a node where a beta cutoff was finally found.
 
-void History::failure(Piece p, Square to) {
+void History::failure(Piece p, Square to, Depth d) {
 
   assert(piece_is_ok(p));
   assert(square_is_ok(to));
 
-  failureCount[p][to]++;
+  history[p][to] -= int(d) * int(d);
+  if (history[p][to] < 0)
+      history[p][to] = 0;
 }
 
 
@@ -91,15 +90,3 @@ int History::move_ordering_score(Piece p, Square to) const {
 
   return history[p][to];
 }
-
-
-/// History::ok_to_prune() decides whether a move has been sufficiently
-/// unsuccessful that it makes sense to prune it entirely.
-
-bool History::ok_to_prune(Piece p, Square to, Depth d) const {
-
-  assert(piece_is_ok(p));
-  assert(square_is_ok(to));
-
-  return (int(d) * successCount[p][to] < failureCount[p][to]);
-}

src/history.h

@@ -47,14 +47,11 @@ public:
   History();
   void clear();
   void success(Piece p, Square to, Depth d);
-  void failure(Piece p, Square to);
+  void failure(Piece p, Square to, Depth d);
   int move_ordering_score(Piece p, Square to) const;
-  bool ok_to_prune(Piece p, Square to, Depth d) const;
 
 private:
   int history[16][64];  // [piece][square]
-  int successCount[16][64];
-  int failureCount[16][64];
 };
 
 
@@ -64,7 +61,7 @@ private:
 
 /// HistoryMax controls how often the history counters will be scaled down:
 /// When the history score for a move gets bigger than HistoryMax, all
-/// entries in the table are divided by 2. It is difficult to guess what
+/// entries in the table are divided by 4. It is difficult to guess what
 /// the ideal value of this constant is. Scaling down the scores often has
 /// the effect that parts of the search tree which have been searched
 /// recently have a bigger importance for move ordering than the moves which

src/main.cpp

@@ -63,7 +63,7 @@ int main(int argc, char *argv[]) {
       if (string(argv[1]) != "bench" || argc < 4 || argc > 8)
           cout << "Usage: stockfish bench <hash size> <threads> "
                << "[time = 60s] [fen positions file = default] "
-               << "[time, depth or node limited = time] "
+               << "[time, depth, perft or node limited = time] "
                << "[timing file name = none]" << endl;
       else
       {

src/material.cpp

@@ -37,10 +37,15 @@ using namespace std;
 
 namespace {
 
+  // Values modified by Joona Kiiski
+  const Value MidgameLimit = Value(15581);
+  const Value EndgameLimit = Value(3998);
+
   // Polynomial material balance parameters
   const Value RedundantQueenPenalty = Value(320);
   const Value RedundantRookPenalty  = Value(554);
-  const int LinearCoefficients[6]   = { 1617, -162, -1172, -190, 105, 26 };
+
+  const int LinearCoefficients[6] = { 1617, -162, -1172, -190, 105, 26 };
 
   const int QuadraticCoefficientsSameColor[][6] = {
   { 7, 7, 7, 7, 7, 7 }, { 39, 2, 7, 7, 7, 7 }, { 35, 271, -4, 7, 7, 7 },
@@ -129,6 +134,22 @@ MaterialInfoTable::~MaterialInfoTable() {
 }
 
 
+/// MaterialInfoTable::game_phase() calculates the phase given the current
+/// position. Because the phase is strictly a function of the material, it
+/// is stored in MaterialInfo.
+
+Phase MaterialInfoTable::game_phase(const Position& pos) {
+
+  Value npm = pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK);
+
+  if (npm >= MidgameLimit)
+      return PHASE_MIDGAME;
+  else if (npm <= EndgameLimit)
+      return PHASE_ENDGAME;
+
+  return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
+}
+
 /// MaterialInfoTable::get_material_info() takes a position object as input,
 /// computes or looks up a MaterialInfo object, and returns a pointer to it.
 /// If the material configuration is not already present in the table, it
@@ -151,6 +172,9 @@ MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
   mi->clear();
   mi->key = key;
 
+  // Store game phase
+  mi->gamePhase = MaterialInfoTable::game_phase(pos);
+
   // Let's look if we have a specialized evaluation function for this
   // particular material configuration. First we look for a fixed
   // configuration one, then a generic one if previous search failed.
@@ -269,8 +293,8 @@ MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
                                  { pos.piece_count(BLACK, BISHOP) > 1, pos.piece_count(BLACK, PAWN), pos.piece_count(BLACK, KNIGHT),
                                    pos.piece_count(BLACK, BISHOP), pos.piece_count(BLACK, ROOK), pos.piece_count(BLACK, QUEEN) } };
   Color c, them;
-  int sign;
-  int matValue = 0;
+  int sign, pt1, pt2, pc;
+  int v, vv, matValue = 0;
 
   for (c = WHITE, sign = 1; c <= BLACK; c++, sign = -sign)
   {
@@ -304,25 +328,27 @@ MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) {
         matValue -= sign * ((pieceCount[c][ROOK] - 1) * RedundantRookPenalty + pieceCount[c][QUEEN] * RedundantQueenPenalty);
 
     them = opposite_color(c);
+    v = 0;
 
     // Second-degree polynomial material imbalance by Tord Romstad
     //
     // We use NO_PIECE_TYPE as a place holder for the bishop pair "extended piece",
     // this allow us to be more flexible in defining bishop pair bonuses.
-    for (int pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; pt1++)
+    for (pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; pt1++)
     {
-        int c1 = sign * pieceCount[c][pt1];
-        if (!c1)
+        pc = pieceCount[c][pt1];
+        if (!pc)
             continue;
 
-        matValue += c1 * LinearCoefficients[pt1];
+        vv = LinearCoefficients[pt1];
 
-        for (int pt2 = NO_PIECE_TYPE; pt2 <= pt1; pt2++)
-        {
-            matValue += c1 * pieceCount[c][pt2] * QuadraticCoefficientsSameColor[pt1][pt2];
-            matValue += c1 * pieceCount[them][pt2] * QuadraticCoefficientsOppositeColor[pt1][pt2];
-        }
+        for (pt2 = NO_PIECE_TYPE; pt2 <= pt1; pt2++)
+            vv +=  pieceCount[c][pt2] * QuadraticCoefficientsSameColor[pt1][pt2]
+                 + pieceCount[them][pt2] * QuadraticCoefficientsOppositeColor[pt1][pt2];
+
+        v += pc * vv;
     }
+    matValue += sign * v;
   }
   mi->value = int16_t(matValue / 16);
   return mi;

src/material.h

@@ -51,9 +51,10 @@ class MaterialInfo {
 public:
   MaterialInfo() : key(0) { clear(); }
 
-  Value material_value() const;
+  Score material_value() const;
   ScaleFactor scale_factor(const Position& pos, Color c) const;
   int space_weight() const;
+  Phase game_phase() const;
   bool specialized_eval_exists() const;
   Value evaluate(const Position& pos) const;
 
@@ -66,6 +67,7 @@ private:
   EndgameEvaluationFunctionBase* evaluationFunction;
   EndgameScalingFunctionBase* scalingFunction[2];
   int spaceWeight;
+  Phase gamePhase;
 };
 
 /// The MaterialInfoTable class represents a pawn hash table. It is basically
@@ -81,6 +83,8 @@ public:
   ~MaterialInfoTable();
   MaterialInfo* get_material_info(const Position& pos);
 
+  static Phase game_phase(const Position& pos);
+
 private:
   unsigned size;
   MaterialInfo* entries;
@@ -92,12 +96,13 @@ private:
 //// Inline functions
 ////
 
+
 /// MaterialInfo::material_value simply returns the material balance
 /// evaluation that is independent from game phase.
 
-inline Value MaterialInfo::material_value() const {
+inline Score MaterialInfo::material_value() const {
 
-  return Value(value);
+  return make_score(value, value);
 }
 
 
@@ -141,6 +146,14 @@ inline int MaterialInfo::space_weight() const {
   return spaceWeight;
 }
 
+/// MaterialInfo::game_phase() returns the game phase according
+/// to this material configuration.
+
+inline Phase MaterialInfo::game_phase() const {
+
+  return gamePhase;
+}
+
 
 /// MaterialInfo::specialized_eval_exists decides whether there is a
 /// specialized evaluation function for the current material configuration,

src/misc.cpp

@@ -50,7 +50,7 @@ using namespace std;
 /// Version number. If this is left empty, the current date (in the format
 /// YYMMDD) is used as a version number.
 
-static const string EngineVersion = "1.5.1";
+static const string EngineVersion = "1.6.1";
 static const string AppName = "Stockfish";
 static const string AppTag  = "";
 

src/move.h

@@ -62,9 +62,103 @@ struct MoveStack {
   int score;
 };
 
-// Note that operator< is set up such that std::sort() will sort in descending order
+// Note that operator< is set up such that sorting will be in descending order
 inline bool operator<(const MoveStack& f, const MoveStack& s) { return s.score < f.score; }
 
+// An helper insertion sort implementation
+template<typename T>
+inline void insertion_sort(T* firstMove, T* lastMove)
+{
+    T value;
+    T *cur, *p, *d;
+
+    if (firstMove != lastMove)
+        for (cur = firstMove + 1; cur != lastMove; cur++)
+        {
+            p = d = cur;
+            value = *p--;
+            if (value < *p)
+            {
+                do *d = *p;
+                while (--d != firstMove && value < *--p);
+                *d = value;
+            }
+        }
+}
+
+// Our dedicated sort in range [firstMove, lastMove), it is well
+// tuned for non-captures where we have a lot of zero scored moves.
+template<typename T>
+inline void sort_moves(T* firstMove, T* lastMove)
+{
+    T tmp;
+    T *p, *d;
+
+    d = lastMove;
+    p = firstMove - 1;
+
+    d->score = -1; // right guard
+
+    // Split positives vs non-positives
+    do {
+        while ((++p)->score > 0);
+
+        if (p != d)
+        {
+            while (--d != p && d->score <= 0);
+
+            tmp = *p;
+            *p = *d;
+            *d = tmp;
+        }
+
+    } while (p != d);
+
+    // Sort positives
+    insertion_sort<T>(firstMove, p);
+
+    d = lastMove;
+    p--;
+
+    // Split zero vs negatives
+    do {
+        while ((++p)->score == 0);
+
+        if (p != d)
+        {
+            while (--d != p && d->score < 0);
+
+            tmp = *p;
+            *p = *d;
+            *d = tmp;
+        }
+
+    } while (p != d);
+
+    // Sort negatives
+    insertion_sort<T>(p, lastMove);
+}
+
+// Picks up the best move in range [curMove, lastMove), one per cycle.
+// It is faster then sorting all the moves in advance when moves are few,
+// as normally are the possible captures. Note that is not a stable alghoritm.
+template<typename T>
+inline T pick_best(T* curMove, T* lastMove)
+{
+    T bestMove, tmp;
+
+    bestMove = *curMove;
+    while (++curMove != lastMove)
+    {
+        if (*curMove < bestMove)
+        {
+            tmp = *curMove;
+            *curMove = bestMove;
+            bestMove = tmp;
+        }
+    }
+    return bestMove;
+}
 
 ////
 //// Inline functions
@@ -82,6 +176,10 @@ inline PieceType move_promotion_piece(Move m) {
   return PieceType((int(m) >> 12) & 7);
 }
 
+inline int move_is_special(Move m) {
+  return m & (0x1F << 12);
+}
+
 inline int move_is_promotion(Move m) {
   return m & (7 << 12);
 }

src/movegen.cpp

@@ -52,16 +52,12 @@ namespace {
     EVASION
   };
 
-  // Functions
-  bool castling_is_check(const Position&, CastlingSide);
-
   // Helper templates
   template<CastlingSide Side>
   MoveStack* generate_castle_moves(const Position&, MoveStack*);
 
   template<Color Us, MoveType Type>
-  MoveStack* generate_pawn_moves(const Position&, MoveStack*, Bitboard = EmptyBoardBB,
-                                 Square = SQ_NONE, Bitboard = EmptyBoardBB);
+  MoveStack* generate_pawn_moves(const Position&, MoveStack*, Bitboard, Square);
 
   // Template generate_piece_moves (captures and non-captures) with specializations and overloads
   template<PieceType>
@@ -71,37 +67,29 @@ namespace {
   MoveStack* generate_piece_moves<KING>(const Position&, MoveStack*, Color, Bitboard);
 
   template<PieceType Piece, MoveType Type>
-  inline MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us) {
+  inline MoveStack* generate_piece_moves(const Position& p, MoveStack* m, Color us, Bitboard t) {
 
     assert(Piece == PAWN);
-    assert(Type == CAPTURE || Type == NON_CAPTURE);
+    assert(Type == CAPTURE || Type == NON_CAPTURE || Type == EVASION);
 
-    return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m)
-                        : generate_pawn_moves<BLACK, Type>(p, m));
+    return (us == WHITE ? generate_pawn_moves<WHITE, Type>(p, m, t, SQ_NONE)
+                        : generate_pawn_moves<BLACK, Type>(p, m, t, SQ_NONE));
   }
 
-  // Template generate_piece_checks with specializations
+  // Templates for non-capture checks generation
+
+  template<PieceType Piece>
+  MoveStack* generate_discovered_checks(const Position&, MoveStack*, Square);
+
   template<PieceType>
-  MoveStack* generate_piece_checks(const Position&, MoveStack*, Color, Bitboard, Square);
+  MoveStack* generate_direct_checks(const Position&, MoveStack*, Color, Bitboard, Square);
 
   template<>
-  inline MoveStack* generate_piece_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
+  inline MoveStack* generate_direct_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
 
     return (us == WHITE ? generate_pawn_moves<WHITE, CHECK>(p, m, dc, ksq)
                         : generate_pawn_moves<BLACK, CHECK>(p, m, dc, ksq));
   }
-
-  // Template generate_piece_evasions with specializations
-  template<PieceType>
-  MoveStack* generate_piece_evasions(const Position&, MoveStack*, Color, Bitboard, Bitboard);
-
-  template<>
-  inline MoveStack* generate_piece_evasions<PAWN>(const Position& p, MoveStack* m,
-                                                  Color us, Bitboard t, Bitboard pnd) {
-
-    return (us == WHITE ? generate_pawn_moves<WHITE, EVASION>(p, m, pnd, SQ_NONE, t)
-                        : generate_pawn_moves<BLACK, EVASION>(p, m, pnd, SQ_NONE, t));
-  }
 }
 
 
@@ -125,7 +113,7 @@ MoveStack* generate_captures(const Position& pos, MoveStack* mlist) {
   mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
   mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
   mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
-  mlist = generate_piece_moves<PAWN, CAPTURE>(pos, mlist, us);
+  mlist = generate_piece_moves<PAWN, CAPTURE>(pos, mlist, us, target);
   return  generate_piece_moves<KING>(pos, mlist, us, target);
 }
 
@@ -141,7 +129,7 @@ MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
   Color us = pos.side_to_move();
   Bitboard target = pos.empty_squares();
 
-  mlist = generate_piece_moves<PAWN, NON_CAPTURE>(pos, mlist, us);
+  mlist = generate_piece_moves<PAWN, NON_CAPTURE>(pos, mlist, us, target);
   mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
   mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
   mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
@@ -152,175 +140,111 @@ MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist) {
 }
 
 
-/// generate_non_capture_checks() generates all pseudo-legal non-captures and
+/// generate_non_capture_checks() generates all pseudo-legal non-captures and knight
 /// underpromotions that give check. Returns a pointer to the end of the move list.
 
-MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc) {
+MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist) {
 
   assert(pos.is_ok());
   assert(!pos.is_check());
 
+  Bitboard b, dc;
+  Square from;
   Color us = pos.side_to_move();
   Square ksq = pos.king_square(opposite_color(us));
 
   assert(pos.piece_on(ksq) == piece_of_color_and_type(opposite_color(us), KING));
 
-  // Pieces moves
-  mlist = generate_piece_checks<PAWN>(pos, mlist, us, dc, ksq);
-  mlist = generate_piece_checks<KNIGHT>(pos, mlist, us, dc, ksq);
-  mlist = generate_piece_checks<BISHOP>(pos, mlist, us, dc, ksq);
-  mlist = generate_piece_checks<ROOK>(pos, mlist, us, dc, ksq);
-  mlist = generate_piece_checks<QUEEN>(pos, mlist, us, dc, ksq);
-  mlist = generate_piece_checks<KING>(pos, mlist, us, dc, ksq);
+  // Discovered non-capture checks
+  b = dc = pos.discovered_check_candidates(us);
 
-  // Castling moves that give check. Very rare but nice to have!
-  if (   pos.can_castle_queenside(us)
-      && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_D)
-      && castling_is_check(pos, QUEEN_SIDE))
-      mlist = generate_castle_moves<QUEEN_SIDE>(pos, mlist);
+  while (b)
+  {
+     from = pop_1st_bit(&b);
+     switch (pos.type_of_piece_on(from))
+     {
+      case PAWN:   /* Will be generated togheter with pawns direct checks */     break;
+      case KNIGHT: mlist = generate_discovered_checks<KNIGHT>(pos, mlist, from); break;
+      case BISHOP: mlist = generate_discovered_checks<BISHOP>(pos, mlist, from); break;
+      case ROOK:   mlist = generate_discovered_checks<ROOK>(pos, mlist, from);   break;
+      case KING:   mlist = generate_discovered_checks<KING>(pos, mlist, from);   break;
+      default: assert(false); break;
+     }
+  }
 
-  if (   pos.can_castle_kingside(us)
-      && (square_rank(ksq) == square_rank(pos.king_square(us)) || square_file(ksq) == FILE_F)
-      && castling_is_check(pos, KING_SIDE))
-      mlist = generate_castle_moves<KING_SIDE>(pos, mlist);
-
-  return mlist;
+  // Direct non-capture checks
+  mlist = generate_direct_checks<PAWN>(pos, mlist, us, dc, ksq);
+  mlist = generate_direct_checks<KNIGHT>(pos, mlist, us, dc, ksq);
+  mlist = generate_direct_checks<BISHOP>(pos, mlist, us, dc, ksq);
+  mlist = generate_direct_checks<ROOK>(pos, mlist, us, dc, ksq);
+  return  generate_direct_checks<QUEEN>(pos, mlist, us, dc, ksq);
 }
 
 
-/// generate_evasions() generates all check evasions when the side to move is
-/// in check. Unlike the other move generation functions, this one generates
-/// only legal moves. Returns a pointer to the end of the move list.
+/// generate_evasions() generates all pseudo-legal check evasions when
+/// the side to move is in check. Returns a pointer to the end of the move list.
 
-MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) {
+MoveStack* generate_evasions(const Position& pos, MoveStack* mlist) {
 
   assert(pos.is_ok());
   assert(pos.is_check());
 
-  Square from, to;
+  Bitboard b, target;
+  Square from, checksq;
+  int checkersCnt = 0;
   Color us = pos.side_to_move();
-  Color them = opposite_color(us);
   Square ksq = pos.king_square(us);
-  Bitboard sliderAttacks = EmptyBoardBB;
   Bitboard checkers = pos.checkers();
+  Bitboard sliderAttacks = EmptyBoardBB;
 
   assert(pos.piece_on(ksq) == piece_of_color_and_type(us, KING));
-
-  // The bitboard of occupied pieces without our king
-  Bitboard b_noKing = pos.occupied_squares();
-  clear_bit(&b_noKing, ksq);
+  assert(checkers);
 
   // Find squares attacked by slider checkers, we will remove
-  // them from the king evasions set so to avoid a couple
-  // of cycles in the slow king evasions legality check loop
-  // and to be able to use attackers_to().
-  Bitboard b = checkers & pos.pieces(BISHOP, QUEEN);
-  while (b)
+  // them from the king evasions set so to early skip known
+  // illegal moves and avoid an useless legality check later.
+  b = checkers;
+  do
   {
-      from = pop_1st_bit(&b);
-      sliderAttacks |= bishop_attacks_bb(from, b_noKing);
-  }
+      checkersCnt++;
+      checksq = pop_1st_bit(&b);
 
-  b = checkers & pos.pieces(ROOK, QUEEN);
-  while (b)
-  {
-      from = pop_1st_bit(&b);
-      sliderAttacks |= rook_attacks_bb(from, b_noKing);
-  }
+      assert(pos.color_of_piece_on(checksq) == opposite_color(us));
+
+      switch (pos.type_of_piece_on(checksq))
+      {
+      case BISHOP: sliderAttacks |= BishopPseudoAttacks[checksq]; break;
+      case ROOK:   sliderAttacks |= RookPseudoAttacks[checksq];   break;
+      case QUEEN:
+          // In case of a queen remove also squares attacked in the other direction to
+          // avoid possible illegal moves when queen and king are on adjacent squares.
+          if (direction_is_straight(checksq, ksq))
+              sliderAttacks |= RookPseudoAttacks[checksq] | pos.attacks_from<BISHOP>(checksq);
+          else
+              sliderAttacks |= BishopPseudoAttacks[checksq] | pos.attacks_from<ROOK>(checksq);
+      default:
+          break;
+      }
+  } while (b);
 
   // Generate evasions for king, capture and non capture moves
-  Bitboard enemy = pos.pieces_of_color(them);
-  Bitboard b1 = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
-  while (b1)
-  {
-      // Note that we can use attackers_to() only because we have already
-      // removed from b1 the squares attacked by slider checkers.
-      to = pop_1st_bit(&b1);
-      if (!(pos.attackers_to(to) & enemy))
-          (*mlist++).move = make_move(ksq, to);
-  }
+  b = pos.attacks_from<KING>(ksq) & ~pos.pieces_of_color(us) & ~sliderAttacks;
+  from = ksq;
+  SERIALIZE_MOVES(b);
 
-  // Generate evasions for other pieces only if not double check. We use a
-  // simple bit twiddling hack here rather than calling count_1s in order to
-  // save some time (we know that pos.checkers() has at most two nonzero bits).
-  if (!(checkers & (checkers - 1))) // Only one bit set?
-  {
-      Square checksq = first_1(checkers);
+  // Generate evasions for other pieces only if not double check
+  if (checkersCnt > 1)
+      return mlist;
 
-      assert(pos.color_of_piece_on(checksq) == them);
+  // Find squares where a blocking evasion or a capture of the
+  // checker piece is possible.
+  target = squares_between(checksq, ksq) | checkers;
 
-      // Generate captures of the checking piece
-
-      // Pawn captures
-      b1 = pos.attacks_from<PAWN>(checksq, them) & pos.pieces(PAWN, us) & ~pinned;
-      while (b1)
-      {
-          from = pop_1st_bit(&b1);
-          if (relative_rank(us, checksq) == RANK_8)
-          {
-              (*mlist++).move = make_promotion_move(from, checksq, QUEEN);
-              (*mlist++).move = make_promotion_move(from, checksq, ROOK);
-              (*mlist++).move = make_promotion_move(from, checksq, BISHOP);
-              (*mlist++).move = make_promotion_move(from, checksq, KNIGHT);
-          } else
-              (*mlist++).move = make_move(from, checksq);
-      }
-
-      // Pieces captures
-      b1 = (  (pos.attacks_from<KNIGHT>(checksq) & pos.pieces(KNIGHT, us))
-            | (pos.attacks_from<BISHOP>(checksq) & pos.pieces(BISHOP, QUEEN, us))
-            | (pos.attacks_from<ROOK>(checksq)   & pos.pieces(ROOK, QUEEN, us)) ) & ~pinned;
-
-      while (b1)
-      {
-          from = pop_1st_bit(&b1);
-          (*mlist++).move = make_move(from, checksq);
-      }
-
-      // Blocking check evasions are possible only if the checking piece is a slider
-      if (sliderAttacks)
-      {
-          Bitboard blockSquares = squares_between(checksq, ksq);
-
-          assert((pos.occupied_squares() & blockSquares) == EmptyBoardBB);
-
-          if (blockSquares)
-          {
-              mlist = generate_piece_evasions<PAWN>(pos, mlist, us, blockSquares, pinned);
-              mlist = generate_piece_evasions<KNIGHT>(pos, mlist, us, blockSquares, pinned);
-              mlist = generate_piece_evasions<BISHOP>(pos, mlist, us, blockSquares, pinned);
-              mlist = generate_piece_evasions<ROOK>(pos, mlist, us, blockSquares, pinned);
-              mlist = generate_piece_evasions<QUEEN>(pos, mlist, us, blockSquares, pinned);
-          }
-      }
-
-      // Finally, the special case of en passant captures. An en passant
-      // capture can only be a check evasion if the check is not a discovered
-      // check. If pos.ep_square() is set, the last move made must have been
-      // a double pawn push. If, furthermore, the checking piece is a pawn,
-      // an en passant check evasion may be possible.
-      if (pos.ep_square() != SQ_NONE && (checkers & pos.pieces(PAWN, them)))
-      {
-          to = pos.ep_square();
-          b1 = pos.attacks_from<PAWN>(to, them) & pos.pieces(PAWN, us);
-
-          // The checking pawn cannot be a discovered (bishop) check candidate
-          // otherwise we were in check also before last double push move.
-          assert(!bit_is_set(pos.discovered_check_candidates(them), checksq));
-          assert(count_1s(b1) == 1 || count_1s(b1) == 2);
-
-          b1 &= ~pinned;
-          while (b1)
-          {
-              from = pop_1st_bit(&b1);
-              // Move is always legal because checking pawn is not a discovered
-              // check candidate and our capturing pawn has been already tested
-              // against pinned pieces.
-              (*mlist++).move = make_ep_move(from, to);
-          }
-      }
-  }
-  return mlist;
+  mlist = generate_piece_moves<PAWN, EVASION>(pos, mlist, us, target);
+  mlist = generate_piece_moves<KNIGHT>(pos, mlist, us, target);
+  mlist = generate_piece_moves<BISHOP>(pos, mlist, us, target);
+  mlist = generate_piece_moves<ROOK>(pos, mlist, us, target);
+  return  generate_piece_moves<QUEEN>(pos, mlist, us, target);
 }
 
 
@@ -332,24 +256,25 @@ MoveStack* generate_moves(const Position& pos, MoveStack* mlist, bool pseudoLega
 
   assert(pos.is_ok());
 
+  MoveStack *last, *cur = mlist;
   Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
 
-  if (pos.is_check())
-      return generate_evasions(pos, mlist, pinned);
-
   // Generate pseudo-legal moves
-  MoveStack* last = generate_captures(pos, mlist);
-  last = generate_noncaptures(pos, last);
+  if (pos.is_check())
+      last = generate_evasions(pos, mlist);
+  else
+      last = generate_noncaptures(pos, generate_captures(pos, mlist));
+
   if (pseudoLegal)
       return last;
 
   // Remove illegal moves from the list
-  for (MoveStack* cur = mlist; cur != last; cur++)
-      if (!pos.pl_move_is_legal(cur->move, pinned))
-      {
+  while (cur != last)
+      if (pos.pl_move_is_legal(cur->move, pinned))
+          cur++;
+      else
           cur->move = (--last)->move;
-          cur--;
-      }
+
   return last;
 }
 
@@ -361,10 +286,11 @@ MoveStack* generate_moves(const Position& pos, MoveStack* mlist, bool pseudoLega
 bool move_is_legal(const Position& pos, const Move m) {
 
   MoveStack mlist[256];
-  MoveStack* last = generate_moves(pos, mlist, true);
-  for (MoveStack* cur = mlist; cur != last; cur++)
+  MoveStack *cur, *last = generate_moves(pos, mlist, true);
+
+   for (cur = mlist; cur != last; cur++)
       if (cur->move == m)
-          return pos.pl_move_is_legal(m);
+          return pos.pl_move_is_legal(m, pos.pinned_pieces(pos.side_to_move()));
 
   return false;
 }
@@ -372,25 +298,23 @@ bool move_is_legal(const Position& pos, const Move m) {
 
 /// Fast version of move_is_legal() that takes a position a move and a
 /// bitboard of pinned pieces as input, and tests whether the move is legal.
-/// This version must only be used when the side to move is not in check.
 
 bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
 
   assert(pos.is_ok());
-  assert(!pos.is_check());
   assert(move_is_ok(m));
   assert(pinned == pos.pinned_pieces(pos.side_to_move()));
 
-  // Use a slower but simpler function for uncommon cases
-  if (move_is_ep(m) || move_is_castle(m))
-      return move_is_legal(pos, m);
-
   Color us = pos.side_to_move();
   Color them = opposite_color(us);
   Square from = move_from(m);
   Square to = move_to(m);
   Piece pc = pos.piece_on(from);
 
+  // Use a slower but simpler function for uncommon cases
+  if (move_is_ep(m) || move_is_castle(m))
+      return move_is_legal(pos, m);
+
   // If the from square is not occupied by a piece belonging to the side to
   // move, the move is obviously not legal.
   if (color_of_piece(pc) != us)
@@ -459,13 +383,13 @@ bool move_is_legal(const Position& pos, const Move m, Bitboard pinned) {
           return false;
       }
       // The move is pseudo-legal, check if it is also legal
-      return pos.pl_move_is_legal(m, pinned);
+      return pos.is_check() ? pos.pl_move_is_evasion(m, pinned) : pos.pl_move_is_legal(m, pinned);
   }
 
   // Luckly we can handle all the other pieces in one go
-  return (   bit_is_set(pos.attacks_from(pc, from), to)
-          && pos.pl_move_is_legal(m, pinned)
-          && !move_is_promotion(m));
+  return    bit_is_set(pos.attacks_from(pc, from), to)
+        && (pos.is_check() ? pos.pl_move_is_evasion(m, pinned) : pos.pl_move_is_legal(m, pinned))
+        && !move_is_promotion(m);
 }
 
 
@@ -474,8 +398,8 @@ namespace {
   template<PieceType Piece>
   MoveStack* generate_piece_moves(const Position& pos, MoveStack* mlist, Color us, Bitboard target) {
 
-    Square from;
     Bitboard b;
+    Square from;
     const Square* ptr = pos.piece_list_begin(us, Piece);
 
     while ((from = *ptr++) != SQ_NONE)
@@ -497,24 +421,6 @@ namespace {
     return mlist;
   }
 
-  template<PieceType Piece>
-  MoveStack* generate_piece_evasions(const Position& pos, MoveStack* mlist,
-                                     Color us, Bitboard target, Bitboard pinned) {
-    Square from;
-    Bitboard b;
-    const Square* ptr = pos.piece_list_begin(us, Piece);
-
-    while ((from = *ptr++) != SQ_NONE)
-    {
-        if (pinned && bit_is_set(pinned, from))
-            continue;
-
-        b = pos.attacks_from<Piece>(from) & target;
-        SERIALIZE_MOVES(b);
-    }
-    return mlist;
-  }
-
   template<Color Us, SquareDelta Direction>
   inline Bitboard move_pawns(Bitboard p) {
 
@@ -528,8 +434,8 @@ namespace {
         return p;
   }
 
-  template<Color Us, SquareDelta Diagonal>
-  MoveStack* generate_pawn_diagonal_captures(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces, bool promotion) {
+  template<Color Us, MoveType Type, SquareDelta Diagonal>
+  inline MoveStack* generate_pawn_captures(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces) {
 
     // Calculate our parametrized parameters at compile time
     const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
@@ -538,136 +444,152 @@ namespace {
     const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
     const SquareDelta TTDELTA_NE = (Diagonal == DELTA_NE ? TDELTA_NE : TDELTA_NW);
 
+    Bitboard b1, b2;
     Square to;
 
     // Captures in the a1-h8 (a8-h1 for black) diagonal or in the h1-a8 (h8-a1 for black)
-    Bitboard b1 = move_pawns<Us, Diagonal>(pawns) & ~TFileABB & enemyPieces;
+    b1 = move_pawns<Us, Diagonal>(pawns) & ~TFileABB & enemyPieces;
 
-    // Capturing promotions
-    if (promotion)
+    // Capturing promotions and under-promotions
+    if (b1 & TRank8BB)
     {
-        Bitboard b2 = b1 & TRank8BB;
+        b2 = b1 & TRank8BB;
         b1 &= ~TRank8BB;
         while (b2)
         {
             to = pop_1st_bit(&b2);
-            (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, QUEEN);
+
+            if (Type == CAPTURE || Type == EVASION)
+                (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, QUEEN);
+
+            if (Type == NON_CAPTURE || Type == EVASION)
+            {
+                (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, ROOK);
+                (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, BISHOP);
+                (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, KNIGHT);
+            }
+
+            // This is the only possible under promotion that can give a check
+            // not already included in the queen-promotion. It is not sure that
+            // the promoted knight will give check, but it doesn't worth to verify.
+            if (Type == CHECK)
+                (*mlist++).move = make_promotion_move(to - TTDELTA_NE, to, KNIGHT);
         }
     }
 
-    // Capturing non-promotions
-    SERIALIZE_MOVES_D(b1, -TTDELTA_NE);
+    // Serialize standard captures
+    if (Type == CAPTURE || Type == EVASION)
+        SERIALIZE_MOVES_D(b1, -TTDELTA_NE);
+
     return mlist;
   }
 
   template<Color Us, MoveType Type>
-  MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard dcp,
-                                 Square ksq, Bitboard blockSquares) {
+  MoveStack* generate_pawn_moves(const Position& pos, MoveStack* mlist, Bitboard target, Square ksq) {
 
     // Calculate our parametrized parameters at compile time
     const Color Them = (Us == WHITE ? BLACK : WHITE);
     const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
     const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
     const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
-    const SquareDelta TDELTA_NE = (Us == WHITE ? DELTA_NE : DELTA_SE);
-    const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
     const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
 
-    Bitboard b1, b2, dcPawns1, dcPawns2;
     Square to;
-    Bitboard pawns = (Type == EVASION ? pos.pieces(PAWN, Us) & ~dcp : pos.pieces(PAWN, Us));
-    bool possiblePromotion = pawns & TRank7BB;
+    Bitboard b1, b2, enemyPieces, emptySquares;
+    Bitboard pawns = pos.pieces(PAWN, Us);
 
-    if (Type == CAPTURE)
+    // Standard captures and capturing promotions and underpromotions
+    if (Type == CAPTURE || Type == EVASION || (pawns & TRank7BB))
     {
-        // Standard captures and capturing promotions in both directions
-        Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
-        mlist = generate_pawn_diagonal_captures<Us, DELTA_NE>(mlist, pawns, enemyPieces, possiblePromotion);
-        mlist = generate_pawn_diagonal_captures<Us, DELTA_NW>(mlist, pawns, enemyPieces, possiblePromotion);
+        enemyPieces = (Type == CAPTURE ? target : pos.pieces_of_color(opposite_color(Us)));
+
+        if (Type == EVASION)
+            enemyPieces &= target; // Capture only the checker piece
+
+        mlist = generate_pawn_captures<Us, Type, DELTA_NE>(mlist, pawns, enemyPieces);
+        mlist = generate_pawn_captures<Us, Type, DELTA_NW>(mlist, pawns, enemyPieces);
     }
 
-    if (possiblePromotion)
+    // Non-capturing promotions and underpromotions
+    if (pawns & TRank7BB)
     {
-        // When generating checks consider under-promotion moves (both captures
-        // and non captures) only if can give a discovery check. Note that dcp
-        // is dc bitboard or pinned bitboard when Type == EVASION.
-        Bitboard pp = (Type == CHECK ? pawns & dcp : pawns);
+        b1 = move_pawns<Us, DELTA_N>(pawns) & TRank8BB & pos.empty_squares();
 
-        if (Type != EVASION && Type != CAPTURE)
-        {
-            Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
-
-            // Underpromotion captures in the a1-h8 (a8-h1 for black) direction
-            b1 = move_pawns<Us, DELTA_NE>(pp) & ~FileABB & enemyPieces & TRank8BB;
-            while (b1)
-            {
-                to = pop_1st_bit(&b1);
-                (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, ROOK);
-                (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, BISHOP);
-                (*mlist++).move = make_promotion_move(to - TDELTA_NE, to, KNIGHT);
-            }
-
-            // Underpromotion captures in the h1-a8 (h8-a1 for black) direction
-            b1 = move_pawns<Us, DELTA_NW>(pp) & ~FileHBB & enemyPieces & TRank8BB;
-            while (b1)
-            {
-                to = pop_1st_bit(&b1);
-                (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, ROOK);
-                (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, BISHOP);
-                (*mlist++).move = make_promotion_move(to - TDELTA_NW, to, KNIGHT);
-            }
-        }
-
-        // Underpromotion pawn pushes. Also queen promotions for evasions and captures.
-        b1 = move_pawns<Us, DELTA_N>(pp) & TRank8BB;
-        b1 &= (Type == EVASION ? blockSquares : pos.empty_squares());
+        if (Type == EVASION)
+            b1 &= target; // Only blocking promotion pushes
 
         while (b1)
         {
             to = pop_1st_bit(&b1);
-            if (Type == EVASION || Type == CAPTURE)
+
+            if (Type == CAPTURE || Type == EVASION)
                 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, QUEEN);
 
-            if (Type != CAPTURE)
+            if (Type == NON_CAPTURE || Type == EVASION)
             {
                 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, ROOK);
                 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, BISHOP);
                 (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
             }
+
+            // This is the only possible under promotion that can give a check
+            // not already included in the queen-promotion.
+            if (Type == CHECK && bit_is_set(pos.attacks_from<KNIGHT>(to), pos.king_square(Them)))
+                (*mlist++).move = make_promotion_move(to - TDELTA_N, to, KNIGHT);
         }
     }
 
+    // Standard pawn pushes and double pushes
     if (Type != CAPTURE)
     {
-        Bitboard emptySquares = pos.empty_squares();
-        dcPawns1 = dcPawns2 = EmptyBoardBB;
-        if (Type == CHECK && (pawns & dcp))
-        {
-            // Pawn moves which gives discovered check. This is possible only if the
-            // pawn is not on the same file as the enemy king, because we don't
-            // generate captures.
-            dcPawns1 = move_pawns<Us, DELTA_N>(pawns & dcp & ~file_bb(ksq)) & emptySquares & ~TRank8BB;
-            dcPawns2 = move_pawns<Us, DELTA_N>(dcPawns1 & TRank3BB) & emptySquares;
-        }
+        emptySquares = (Type == NON_CAPTURE ? target : pos.empty_squares());
 
-        // Single pawn pushes
+        // Single and double pawn pushes
         b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares & ~TRank8BB;
-        b2 = (Type == CHECK ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns1 :
-              (Type == EVASION ? b1 & blockSquares : b1));
-        SERIALIZE_MOVES_D(b2, -TDELTA_N);
+        b2 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
 
-        // Double pawn pushes
-        b1 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
-        b2 = (Type == CHECK ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns2 :
-              (Type == EVASION ? b1 & blockSquares : b1));
+        // Filter out unwanted pushes according to the move type
+        if (Type == EVASION)
+        {
+            b1 &= target;
+            b2 &= target;
+        }
+        else if (Type == CHECK)
+        {
+            // Pawn moves which give direct cheks
+            b1 &= pos.attacks_from<PAWN>(ksq, Them);
+            b2 &= pos.attacks_from<PAWN>(ksq, Them);
+
+            // Pawn moves which gives discovered check. This is possible only if
+            // the pawn is not on the same file as the enemy king, because we
+            //  don't generate captures.
+            if (pawns & target) // For CHECK type target is dc bitboard
+            {
+                Bitboard dc1 = move_pawns<Us, DELTA_N>(pawns & target & ~file_bb(ksq)) & emptySquares & ~TRank8BB;
+                Bitboard dc2 = move_pawns<Us, DELTA_N>(dc1 & TRank3BB) & emptySquares;
+
+                b1 |= dc1;
+                b2 |= dc2;
+            }
+        }
+        SERIALIZE_MOVES_D(b1, -TDELTA_N);
         SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
     }
-    else if (pos.ep_square() != SQ_NONE) // En passant captures
+
+    // En passant captures
+    if ((Type == CAPTURE || Type == EVASION) && pos.ep_square() != SQ_NONE)
     {
         assert(Us != WHITE || square_rank(pos.ep_square()) == RANK_6);
         assert(Us != BLACK || square_rank(pos.ep_square()) == RANK_3);
 
+        // An en passant capture can be an evasion only if the checking piece
+        // is the double pushed pawn and so is in the target. Otherwise this
+        // is a discovery check and we are forced to do otherwise.
+        if (Type == EVASION && !bit_is_set(target, pos.ep_square() - TDELTA_N))
+            return mlist;
+
         b1 = pawns & pos.attacks_from<PAWN>(pos.ep_square(), Them);
+
         assert(b1 != EmptyBoardBB);
 
         while (b1)
@@ -680,43 +602,49 @@ namespace {
   }
 
   template<PieceType Piece>
-  MoveStack* generate_piece_checks(const Position& pos, MoveStack* mlist, Color us,
+  MoveStack* generate_discovered_checks(const Position& pos, MoveStack* mlist, Square from) {
+
+    assert(Piece != QUEEN);
+
+    Bitboard b = pos.attacks_from<Piece>(from) & pos.empty_squares();
+    if (Piece == KING)
+    {
+        Square ksq = pos.king_square(opposite_color(pos.side_to_move()));
+        b &= ~QueenPseudoAttacks[ksq];
+    }
+    SERIALIZE_MOVES(b);
+    return mlist;
+  }
+
+  template<PieceType Piece>
+  MoveStack* generate_direct_checks(const Position& pos, MoveStack* mlist, Color us,
                                    Bitboard dc, Square ksq) {
+    assert(Piece != KING);
 
-    Bitboard target = pos.pieces(Piece, us);
+    Bitboard checkSqs, b;
+    Square from;
+    const Square* ptr = pos.piece_list_begin(us, Piece);
 
-    // Discovered non-capture checks
-    Bitboard b = target & dc;
+    if ((from = *ptr++) == SQ_NONE)
+        return mlist;
 
-    assert(Piece != QUEEN || !b);
+    checkSqs = pos.attacks_from<Piece>(ksq) & pos.empty_squares();
 
-    while (b)
+    do
     {
-        Square from = pop_1st_bit(&b);
-        Bitboard bb = pos.attacks_from<Piece>(from) & pos.empty_squares();
-        if (Piece == KING)
-            bb &= ~QueenPseudoAttacks[ksq];
+        if (   (Piece == QUEEN  && !(QueenPseudoAttacks[from]  & checkSqs))
+            || (Piece == ROOK   && !(RookPseudoAttacks[from]   & checkSqs))
+            || (Piece == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
+            continue;
 
-        SERIALIZE_MOVES(bb);
-    }
+        if (dc && bit_is_set(dc, from))
+            continue;
 
-    // Direct non-capture checks
-    b = target & ~dc;
-    Bitboard checkSqs = pos.attacks_from<Piece>(ksq) & pos.empty_squares();
-    if (Piece != KING && checkSqs)
-    {
-        while (b)
-        {
-            Square from = pop_1st_bit(&b);
-            if (   (Piece == QUEEN  && !(QueenPseudoAttacks[from]  & checkSqs))
-                || (Piece == ROOK   && !(RookPseudoAttacks[from]   & checkSqs))
-                || (Piece == BISHOP && !(BishopPseudoAttacks[from] & checkSqs)))
-                continue;
+        b = pos.attacks_from<Piece>(from) & checkSqs;
+        SERIALIZE_MOVES(b);
+
+    } while ((from = *ptr++) != SQ_NONE);
 
-            Bitboard bb = pos.attacks_from<Piece>(from) & checkSqs;
-            SERIALIZE_MOVES(bb);
-        }
-    }
     return mlist;
   }
 
@@ -762,17 +690,4 @@ namespace {
     }
     return mlist;
   }
-
-  bool castling_is_check(const Position& pos, CastlingSide side) {
-
-    // After castling opponent king is attacked by the castled rook?
-    File rookFile = (side == QUEEN_SIDE ? FILE_D : FILE_F);
-    Color us = pos.side_to_move();
-    Square ksq = pos.king_square(us);
-    Bitboard occ = pos.occupied_squares();
-
-    clear_bit(&occ, ksq); // Remove our king from the board
-    Square rsq = make_square(rookFile, square_rank(ksq));
-    return bit_is_set(rook_attacks_bb(rsq, occ), pos.king_square(opposite_color(us)));
-  }
 }

src/movegen.h

@@ -34,8 +34,8 @@
 
 extern MoveStack* generate_captures(const Position& pos, MoveStack* mlist);
 extern MoveStack* generate_noncaptures(const Position& pos, MoveStack* mlist);
-extern MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist, Bitboard dc);
-extern MoveStack* generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned);
+extern MoveStack* generate_non_capture_checks(const Position& pos, MoveStack* mlist);
+extern MoveStack* generate_evasions(const Position& pos, MoveStack* mlist);
 extern MoveStack* generate_moves(const Position& pos, MoveStack* mlist, bool pseudoLegal = false);
 extern bool move_is_legal(const Position& pos, const Move m, Bitboard pinned);
 extern bool move_is_legal(const Position& pos, const Move m);

src/movepick.cpp

@@ -23,7 +23,6 @@
 //// Includes
 ////
 
-#include <algorithm>
 #include <cassert>
 
 #include "history.h"
@@ -53,7 +52,7 @@ namespace {
 
   CACHE_LINE_ALIGNMENT
   const uint8_t MainSearchPhaseTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP};
-  const uint8_t EvasionsPhaseTable[] = { PH_EVASIONS, PH_STOP};
+  const uint8_t EvasionsPhaseTable[] = { PH_TT_MOVES, PH_EVASIONS, PH_STOP};
   const uint8_t QsearchWithChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP};
   const uint8_t QsearchWithoutChecksPhaseTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP};
 }
@@ -78,7 +77,9 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
   finished = false;
   lastBadCapture = badCaptures;
 
-  if (ss)
+  pinned = p.pinned_pieces(pos.side_to_move());
+
+  if (ss && !p.is_check())
   {
       ttMoves[1].move = (ss->mateKiller == ttm)? MOVE_NONE : ss->mateKiller;
       searchTT |= ttMoves[1].move;
@@ -87,21 +88,16 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
   } else
       ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE;
 
-  Color us = pos.side_to_move();
-
-  dc = p.discovered_check_candidates(us);
-  pinned = p.pinned_pieces(us);
-
   if (p.is_check())
       phasePtr = EvasionsPhaseTable;
   else if (d > Depth(0))
-      phasePtr = MainSearchPhaseTable + !searchTT;
+      phasePtr = MainSearchPhaseTable;
   else if (d == Depth(0))
-      phasePtr = QsearchWithChecksPhaseTable + !searchTT;
+      phasePtr = QsearchWithChecksPhaseTable;
   else
-      phasePtr = QsearchWithoutChecksPhaseTable + !searchTT;
+      phasePtr = QsearchWithoutChecksPhaseTable;
 
-  phasePtr--;
+  phasePtr += !searchTT - 1;
   go_next_phase();
 }
 
@@ -123,7 +119,6 @@ void MovePicker::go_next_phase() {
   case PH_GOOD_CAPTURES:
       lastMove = generate_captures(pos, moves);
       score_captures();
-      std::sort(moves, lastMove);
       return;
 
   case PH_KILLERS:
@@ -134,7 +129,7 @@ void MovePicker::go_next_phase() {
   case PH_NONCAPTURES:
       lastMove = generate_noncaptures(pos, moves);
       score_noncaptures();
-      std::sort(moves, lastMove);
+      sort_moves(moves, lastMove);
       return;
 
   case PH_BAD_CAPTURES:
@@ -142,25 +137,22 @@ void MovePicker::go_next_phase() {
       // to get SEE move ordering.
       curMove = badCaptures;
       lastMove = lastBadCapture;
-      std::sort(badCaptures, lastMove);
       return;
 
   case PH_EVASIONS:
       assert(pos.is_check());
-      lastMove = generate_evasions(pos, moves, pinned);
+      lastMove = generate_evasions(pos, moves);
       score_evasions();
-      std::sort(moves, lastMove);
       return;
 
   case PH_QCAPTURES:
       lastMove = generate_captures(pos, moves);
       score_captures();
-      std::sort(moves, lastMove);
       return;
 
   case PH_QCHECKS:
       // Perhaps we should order moves move here?  FIXME
-      lastMove = generate_non_capture_checks(pos, moves, dc);
+      lastMove = generate_non_capture_checks(pos, moves);
       return;
 
   case PH_STOP:
@@ -202,8 +194,8 @@ void MovePicker::score_captures() {
       if (move_is_promotion(m))
           cur->score = QueenValueMidgame;
       else
-          cur->score = int(pos.midgame_value_of_piece_on(move_to(m)))
-                      -int(pos.type_of_piece_on(move_from(m)));
+          cur->score =  pos.midgame_value_of_piece_on(move_to(m))
+                      - pos.type_of_piece_on(move_from(m));
   }
 }
 
@@ -229,24 +221,27 @@ void MovePicker::score_noncaptures() {
           hs += 1000;
 
       // pst based scoring
-      cur->score = hs + pos.pst_delta<Position::MidGame>(piece, from, to);
+      cur->score = hs + mg_value(pos.pst_delta(piece, from, to));
   }
 }
 
 void MovePicker::score_evasions() {
-
+  // Try good captures ordered by MVV/LVA, then non-captures if
+  // destination square is not under attack, ordered by history
+  // value, and at the end bad-captures and non-captures with a
+  // negative SEE. This last group is ordered by the SEE score.
   Move m;
+  int seeScore;
 
   for (MoveStack* cur = moves; cur != lastMove; cur++)
   {
       m = cur->move;
-      if (m == ttMoves[0].move)
-          cur->score = 2 * HistoryMax;
-      else if (!pos.square_is_empty(move_to(m)))
-      {
-          int seeScore = pos.see(m);
-          cur->score = seeScore + (seeScore >= 0 ? HistoryMax : 0);
-      } else
+      if ((seeScore = pos.see_sign(m)) < 0)
+          cur->score = seeScore;
+      else if (pos.move_is_capture(m))
+          cur->score =  pos.midgame_value_of_piece_on(move_to(m))
+                      - pos.type_of_piece_on(move_from(m)) + HistoryMax;
+      else
           cur->score = H.move_ordering_score(pos.piece_on(move_from(m)), move_to(m));
   }
 }
@@ -259,26 +254,23 @@ void MovePicker::score_evasions() {
 
 Move MovePicker::get_next_move() {
 
-  assert(!pos.is_check() || *phasePtr == PH_EVASIONS || *phasePtr == PH_STOP);
-  assert( pos.is_check() || *phasePtr != PH_EVASIONS);
-
   Move move;
 
   while (true)
   {
       while (curMove != lastMove)
       {
-          move = (curMove++)->move;
-
           switch (phase) {
 
           case PH_TT_MOVES:
+              move = (curMove++)->move;
               if (   move != MOVE_NONE
                   && move_is_legal(pos, move, pinned))
                   return move;
               break;
 
           case PH_GOOD_CAPTURES:
+              move = pick_best(curMove++, lastMove).move;
               if (   move != ttMoves[0].move
                   && move != ttMoves[1].move
                   && pos.pl_move_is_legal(move, pinned))
@@ -298,6 +290,7 @@ Move MovePicker::get_next_move() {
               break;
 
           case PH_KILLERS:
+              move = (curMove++)->move;
               if (   move != MOVE_NONE
                   && move != ttMoves[0].move
                   && move != ttMoves[1].move
@@ -307,6 +300,7 @@ Move MovePicker::get_next_move() {
               break;
 
           case PH_NONCAPTURES:
+              move = (curMove++)->move;
               if (   move != ttMoves[0].move
                   && move != ttMoves[1].move
                   && move != killers[0].move
@@ -315,13 +309,20 @@ Move MovePicker::get_next_move() {
                   return move;
               break;
 
-          case PH_EVASIONS:
           case PH_BAD_CAPTURES:
+              move = pick_best(curMove++, lastMove).move;
               return move;
 
+          case PH_EVASIONS:
           case PH_QCAPTURES:
+              move = pick_best(curMove++, lastMove).move;
+              if (   move != ttMoves[0].move
+                  && pos.pl_move_is_legal(move, pinned))
+                  return move;
+              break;
+
           case PH_QCHECKS:
-              // Maybe postpone the legality check until after futility pruning?
+              move = (curMove++)->move;
               if (   move != ttMoves[0].move
                   && pos.pl_move_is_legal(move, pinned))
                   return move;

src/movepick.h

@@ -54,7 +54,6 @@ public:
   Move get_next_move();
   Move get_next_move(Lock& lock);
   int number_of_evasions() const;
-  Bitboard discovered_check_candidates() const;
 
 private:
   void score_captures();
@@ -69,7 +68,7 @@ private:
   int phase;
   const uint8_t* phasePtr;
   MoveStack *curMove, *lastMove, *lastBadCapture;
-  Bitboard dc, pinned;
+  Bitboard pinned;
   MoveStack moves[256], badCaptures[64];
 };
 
@@ -88,12 +87,4 @@ inline int MovePicker::number_of_evasions() const {
   return int(lastMove - moves);
 }
 
-/// MovePicker::discovered_check_candidates() returns a bitboard containing
-/// all pieces which can possibly give discovered check. This bitboard is
-/// computed by the constructor function.
-
-inline Bitboard MovePicker::discovered_check_candidates() const {
-  return dc;
-}
-
 #endif // !defined(MOVEPICK_H_INCLUDED)

src/pawns.cpp

@@ -38,64 +38,36 @@ namespace {
 
   /// Constants and variables
 
-  // Doubled pawn penalty by file, middle game
-  const Value DoubledPawnMidgamePenalty[8] = {
-    Value(13), Value(20), Value(23), Value(23),
-    Value(23), Value(23), Value(20), Value(13)
+  #define S(mg, eg) make_score(mg, eg)
+
+  // Doubled pawn penalty by file
+  const Score DoubledPawnPenalty[8] = {
+    S(13, 43), S(20, 48), S(23, 48), S(23, 48),
+    S(23, 48), S(23, 48), S(20, 48), S(13, 43)
   };
 
-  // Doubled pawn penalty by file, endgame
-  const Value DoubledPawnEndgamePenalty[8] = {
-    Value(43), Value(48), Value(48), Value(48),
-    Value(48), Value(48), Value(48), Value(43)
+  // Isolated pawn penalty by file
+  const Score IsolatedPawnPenalty[8] = {
+    S(25, 30), S(36, 35), S(40, 35), S(40, 35),
+    S(40, 35), S(40, 35), S(36, 35), S(25, 30)
   };
 
-  // Isolated pawn penalty by file, middle game
-  const Value IsolatedPawnMidgamePenalty[8] = {
-    Value(25), Value(36), Value(40), Value(40),
-    Value(40), Value(40), Value(36), Value(25)
+  // Backward pawn penalty by file
+  const Score BackwardPawnPenalty[8] = {
+    S(20, 28), S(29, 31), S(33, 31), S(33, 31),
+    S(33, 31), S(33, 31), S(29, 31), S(20, 28)
   };
 
-  // Isolated pawn penalty by file, endgame
-  const Value IsolatedPawnEndgamePenalty[8] = {
-    Value(30), Value(35), Value(35), Value(35),
-    Value(35), Value(35), Value(35), Value(30)
+  // Pawn chain membership bonus by file
+  const Score ChainBonus[8] = {
+    S(11,-1), S(13,-1), S(13,-1), S(14,-1),
+    S(14,-1), S(13,-1), S(13,-1), S(11,-1)
   };
 
-  // Backward pawn penalty by file, middle game
-  const Value BackwardPawnMidgamePenalty[8] = {
-    Value(20), Value(29), Value(33), Value(33),
-    Value(33), Value(33), Value(29), Value(20)
-  };
-
-  // Backward pawn penalty by file, endgame
-  const Value BackwardPawnEndgamePenalty[8] = {
-    Value(28), Value(31), Value(31), Value(31),
-    Value(31), Value(31), Value(31), Value(28)
-  };
-
-  // Pawn chain membership bonus by file, middle game
-  const Value ChainMidgameBonus[8] = {
-    Value(11), Value(13), Value(13), Value(14),
-    Value(14), Value(13), Value(13), Value(11)
-  };
-
-  // Pawn chain membership bonus by file, endgame
-  const Value ChainEndgameBonus[8] = {
-    Value(-1), Value(-1), Value(-1), Value(-1),
-    Value(-1), Value(-1), Value(-1), Value(-1)
-  };
-
-  // Candidate passed pawn bonus by rank, middle game
-  const Value CandidateMidgameBonus[8] = {
-    Value( 0), Value( 6), Value(6), Value(14),
-    Value(34), Value(83), Value(0), Value( 0)
-  };
-
-  // Candidate passed pawn bonus by rank, endgame
-  const Value CandidateEndgameBonus[8] = {
-    Value( 0), Value( 13), Value(13), Value(29),
-    Value(68), Value(166), Value( 0), Value( 0)
+  // Candidate passed pawn bonus by rank
+  const Score CandidateBonus[8] = {
+    S( 0, 0), S( 6, 13), S(6,13), S(14,29),
+    S(34,68), S(83,166), S(0, 0), S( 0, 0)
   };
 
   // Pawn storm tables for positions with opposite castling
@@ -190,207 +162,194 @@ PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) {
   pi->clear();
   pi->key = key;
 
-  Value mgValue[2] = {Value(0), Value(0)};
-  Value egValue[2] = {Value(0), Value(0)};
-
   // Calculate pawn attacks
-  pi->pawnAttacks[WHITE] = ((pos.pieces(PAWN, WHITE) << 9) & ~FileABB) | ((pos.pieces(PAWN, WHITE) << 7) & ~FileHBB);
-  pi->pawnAttacks[BLACK] = ((pos.pieces(PAWN, BLACK) >> 7) & ~FileABB) | ((pos.pieces(PAWN, BLACK) >> 9) & ~FileHBB);
+  Bitboard whitePawns = pos.pieces(PAWN, WHITE);
+  Bitboard blackPawns = pos.pieces(PAWN, BLACK);
+  pi->pawnAttacks[WHITE] = ((whitePawns << 9) & ~FileABB) | ((whitePawns << 7) & ~FileHBB);
+  pi->pawnAttacks[BLACK] = ((blackPawns >> 7) & ~FileABB) | ((blackPawns >> 9) & ~FileHBB);
 
-  // Loop through the pawns for both colors
-  for (Color us = WHITE; us <= BLACK; us++)
-  {
-    Color them = opposite_color(us);
-    Bitboard ourPawns = pos.pieces(PAWN, us);
-    Bitboard theirPawns = pos.pieces(PAWN, them);
-    Bitboard pawns = ourPawns;
-
-    // Initialize pawn storm scores by giving bonuses for open files
-    for (File f = FILE_A; f <= FILE_H; f++)
-        if (!(pawns & file_bb(f)))
-        {
-            pi->ksStormValue[us] += KStormOpenFileBonus[f];
-            pi->qsStormValue[us] += QStormOpenFileBonus[f];
-            pi->halfOpenFiles[us] |= (1 << f);
-        }
-
-    // Loop through all pawns of the current color and score each pawn
-    while (pawns)
-    {
-        Square s = pop_1st_bit(&pawns);
-        File f = square_file(s);
-        Rank r = square_rank(s);
-
-        assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN));
-
-        // Passed, isolated or doubled pawn?
-        bool passed   = Position::pawn_is_passed(theirPawns, us, s);
-        bool isolated = Position::pawn_is_isolated(ourPawns, s);
-        bool doubled  = Position::pawn_is_doubled(ourPawns, us, s);
-
-        // We calculate kingside and queenside pawn storm
-        // scores for both colors. These are used when evaluating
-        // middle game positions with opposite side castling.
-        //
-        // Each pawn is given a base score given by a piece square table
-        // (KStormTable[] or QStormTable[]). Pawns which seem to have good
-        // chances of creating an open file by exchanging itself against an
-        // enemy pawn on an adjacent file gets an additional bonus.
-
-        // Kingside pawn storms
-        int bonus = KStormTable[relative_square(us, s)];
-        if (f >= FILE_F)
-        {
-            Bitboard b = outpost_mask(us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
-            while (b)
-            {
-                Square s2 = pop_1st_bit(&b);
-                if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
-                {
-                    // The enemy pawn has no pawn beside itself, which makes it
-                    // particularly vulnerable. Big bonus, especially against a
-                    // weakness on the rook file.
-                    if (square_file(s2) == FILE_H)
-                        bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2);
-                    else
-                        bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2);
-                } else
-                    // There is at least one enemy pawn beside the enemy pawn we look
-                    // at, which means that the pawn has somewhat better chances of
-                    // defending itself by advancing. Smaller bonus.
-                    bonus += StormLeverBonus[f] - 2*square_distance(s, s2);
-            }
-        }
-        pi->ksStormValue[us] += bonus;
-
-        // Queenside pawn storms
-        bonus = QStormTable[relative_square(us, s)];
-        if (f <= FILE_C)
-        {
-            Bitboard b = outpost_mask(us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
-            while (b)
-            {
-                Square s2 = pop_1st_bit(&b);
-                if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
-                {
-                    // The enemy pawn has no pawn beside itself, which makes it
-                    // particularly vulnerable. Big bonus, especially against a
-                    // weakness on the rook file.
-                    if (square_file(s2) == FILE_A)
-                        bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2);
-                    else
-                        bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2);
-                } else
-                    // There is at least one enemy pawn beside the enemy pawn we look
-                    // at, which means that the pawn has somewhat better chances of
-                    // defending itself by advancing. Smaller bonus.
-                    bonus += StormLeverBonus[f] - 4*square_distance(s, s2);
-            }
-        }
-        pi->qsStormValue[us] += bonus;
-
-        // Member of a pawn chain (but not the backward one)? We could speed up
-        // the test a little by introducing an array of masks indexed by color
-        // and square for doing the test, but because everything is hashed,
-        // it probably won't make any noticable difference.
-        bool chain =  ourPawns
-                    & neighboring_files_bb(f)
-                    & (rank_bb(r) | rank_bb(r - (us == WHITE ? 1 : -1)));
-
-        // Test for backward pawn
-        //
-        // If the pawn is passed, isolated, or member of a pawn chain
-        // it cannot be backward. If can capture an enemy pawn or if
-        // there are friendly pawns behind on neighboring files it cannot
-        // be backward either.
-        bool backward;
-        if (   passed
-            || isolated
-            || chain
-            || (pos.attacks_from<PAWN>(s, us) & theirPawns)
-            || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f)))
-            backward = false;
-        else
-        {
-            // We now know that there are no friendly pawns beside or behind this
-            // pawn on neighboring files. We now check whether the pawn is
-            // backward by looking in the forward direction on the neighboring
-            // files, and seeing whether we meet a friendly or an enemy pawn first.
-            Bitboard b = pos.attacks_from<PAWN>(s, us);
-            if (us == WHITE)
-            {
-                for ( ; !(b & (ourPawns | theirPawns)); b <<= 8);
-                backward = (b | (b << 8)) & theirPawns;
-            }
-            else
-            {
-                for ( ; !(b & (ourPawns | theirPawns)); b >>= 8);
-                backward = (b | (b >> 8)) & theirPawns;
-            }
-        }
-
-        // Test for candidate passed pawn
-        bool candidate;
-        candidate =    !passed
-                    && !(theirPawns & file_bb(f))
-                    && (  count_1s_max_15(neighboring_files_bb(f) & (behind_bb(us, r) | rank_bb(r)) & ourPawns)
-                        - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(us, r)              & theirPawns)
-                        >= 0);
-
-        // In order to prevent doubled passed pawns from receiving a too big
-        // bonus, only the frontmost passed pawn on each file is considered as
-        // a true passed pawn.
-        if (passed && (ourPawns & squares_in_front_of(us, s)))
-            passed = false;
-
-        // Score this pawn
-        if (passed)
-            set_bit(&(pi->passedPawns), s);
-
-        if (isolated)
-        {
-            mgValue[us] -= IsolatedPawnMidgamePenalty[f];
-            egValue[us] -= IsolatedPawnEndgamePenalty[f];
-            if (!(theirPawns & file_bb(f)))
-            {
-                mgValue[us] -= IsolatedPawnMidgamePenalty[f] / 2;
-                egValue[us] -= IsolatedPawnEndgamePenalty[f] / 2;
-            }
-        }
-        if (doubled)
-        {
-            mgValue[us] -= DoubledPawnMidgamePenalty[f];
-            egValue[us] -= DoubledPawnEndgamePenalty[f];
-        }
-        if (backward)
-        {
-            mgValue[us] -= BackwardPawnMidgamePenalty[f];
-            egValue[us] -= BackwardPawnEndgamePenalty[f];
-            if (!(theirPawns & file_bb(f)))
-            {
-                mgValue[us] -= BackwardPawnMidgamePenalty[f] / 2;
-                egValue[us] -= BackwardPawnEndgamePenalty[f] / 2;
-            }
-        }
-        if (chain)
-        {
-            mgValue[us] += ChainMidgameBonus[f];
-            egValue[us] += ChainEndgameBonus[f];
-        }
-        if (candidate)
-        {
-            mgValue[us] += CandidateMidgameBonus[relative_rank(us, s)];
-            egValue[us] += CandidateEndgameBonus[relative_rank(us, s)];
-        }
-    } // while(pawns)
-  } // for(colors)
-
-  pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]);
-  pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]);
+  // Evaluate pawns for both colors
+  pi->value =  evaluate_pawns<WHITE>(pos, whitePawns, blackPawns, pi)
+             - evaluate_pawns<BLACK>(pos, blackPawns, whitePawns, pi);
   return pi;
 }
 
 
+/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+
+template<Color Us>
+Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
+                                    Bitboard theirPawns, PawnInfo* pi) {
+  Square s;
+  File f;
+  Rank r;
+  bool passed, isolated, doubled, chain, backward, candidate;
+  int bonus;
+  Score value = make_score(0, 0);
+  const Square* ptr = pos.piece_list_begin(Us, PAWN);
+
+  // Initialize pawn storm scores by giving bonuses for open files
+  for (f = FILE_A; f <= FILE_H; f++)
+      if (!(ourPawns & file_bb(f)))
+      {
+          pi->ksStormValue[Us] += KStormOpenFileBonus[f];
+          pi->qsStormValue[Us] += QStormOpenFileBonus[f];
+          pi->halfOpenFiles[Us] |= (1 << f);
+      }
+
+  // Loop through all pawns of the current color and score each pawn
+  while ((s = *ptr++) != SQ_NONE)
+  {
+      f = square_file(s);
+      r = square_rank(s);
+
+      assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
+
+      // Passed, isolated or doubled pawn?
+      passed   = Position::pawn_is_passed(theirPawns, Us, s);
+      isolated = Position::pawn_is_isolated(ourPawns, s);
+      doubled  = Position::pawn_is_doubled(ourPawns, Us, s);
+
+      // We calculate kingside and queenside pawn storm
+      // scores for both colors. These are used when evaluating
+      // middle game positions with opposite side castling.
+      //
+      // Each pawn is given a base score given by a piece square table
+      // (KStormTable[] or QStormTable[]). Pawns which seem to have good
+      // chances of creating an open file by exchanging itself against an
+      // enemy pawn on an adjacent file gets an additional bonus.
+
+      // Kingside pawn storms
+      bonus = KStormTable[relative_square(Us, s)];
+      if (f >= FILE_F)
+      {
+          Bitboard b = outpost_mask(Us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
+          while (b)
+          {
+              Square s2 = pop_1st_bit(&b);
+              if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
+              {
+                  // The enemy pawn has no pawn beside itself, which makes it
+                  // particularly vulnerable. Big bonus, especially against a
+                  // weakness on the rook file.
+                  if (square_file(s2) == FILE_H)
+                      bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2);
+                  else
+                      bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2);
+              } else
+                  // There is at least one enemy pawn beside the enemy pawn we look
+                  // at, which means that the pawn has somewhat better chances of
+                  // defending itself by advancing. Smaller bonus.
+                  bonus += StormLeverBonus[f] - 2*square_distance(s, s2);
+          }
+      }
+      pi->ksStormValue[Us] += bonus;
+
+      // Queenside pawn storms
+      bonus = QStormTable[relative_square(Us, s)];
+      if (f <= FILE_C)
+      {
+          Bitboard b = outpost_mask(Us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
+          while (b)
+          {
+              Square s2 = pop_1st_bit(&b);
+              if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
+              {
+                  // The enemy pawn has no pawn beside itself, which makes it
+                  // particularly vulnerable. Big bonus, especially against a
+                  // weakness on the rook file.
+                  if (square_file(s2) == FILE_A)
+                      bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2);
+                  else
+                      bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2);
+              } else
+                  // There is at least one enemy pawn beside the enemy pawn we look
+                  // at, which means that the pawn has somewhat better chances of
+                  // defending itself by advancing. Smaller bonus.
+                  bonus += StormLeverBonus[f] - 4*square_distance(s, s2);
+          }
+      }
+      pi->qsStormValue[Us] += bonus;
+
+      // Member of a pawn chain (but not the backward one)? We could speed up
+      // the test a little by introducing an array of masks indexed by color
+      // and square for doing the test, but because everything is hashed,
+      // it probably won't make any noticable difference.
+      chain =  ourPawns
+             & neighboring_files_bb(f)
+             & (rank_bb(r) | rank_bb(r - (Us == WHITE ? 1 : -1)));
+
+      // Test for backward pawn
+      //
+      // If the pawn is passed, isolated, or member of a pawn chain
+      // it cannot be backward. If can capture an enemy pawn or if
+      // there are friendly pawns behind on neighboring files it cannot
+      // be backward either.
+      if (   (passed | isolated | chain)
+          || (ourPawns & behind_bb(Us, r) & neighboring_files_bb(f))
+          || (pos.attacks_from<PAWN>(s, Us) & theirPawns))
+          backward = false;
+      else
+      {
+          // We now know that there are no friendly pawns beside or behind this
+          // pawn on neighboring files. We now check whether the pawn is
+          // backward by looking in the forward direction on the neighboring
+          // files, and seeing whether we meet a friendly or an enemy pawn first.
+          Bitboard b = pos.attacks_from<PAWN>(s, Us);
+
+          // Note that we are sure to find something because pawn is not passed
+          // nor isolated, so loop is potentially infinite, but it isn't.
+          while (!(b & (ourPawns | theirPawns)))
+              Us == WHITE ? b <<= 8 : b >>= 8;
+
+          // The friendly pawn needs to be at least two ranks closer than the enemy
+          // pawn in order to help the potentially backward pawn advance.
+          backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
+      }
+
+      // Test for candidate passed pawn
+      candidate =   !passed
+                 && !(theirPawns & file_bb(f))
+                 && (  count_1s_max_15(neighboring_files_bb(f) & (behind_bb(Us, r) | rank_bb(r)) & ourPawns)
+                     - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(Us, r)              & theirPawns)
+                     >= 0);
+
+      // In order to prevent doubled passed pawns from receiving a too big
+      // bonus, only the frontmost passed pawn on each file is considered as
+      // a true passed pawn.
+      if (passed && (ourPawns & squares_in_front_of(Us, s)))
+          passed = false;
+
+      // Score this pawn
+      if (passed)
+          set_bit(&(pi->passedPawns), s);
+
+      if (isolated)
+      {
+          value -= IsolatedPawnPenalty[f];
+          if (!(theirPawns & file_bb(f)))
+              value -= IsolatedPawnPenalty[f] / 2;
+      }
+      if (doubled)
+          value -= DoubledPawnPenalty[f];
+
+      if (backward)
+      {
+          value -= BackwardPawnPenalty[f];
+          if (!(theirPawns & file_bb(f)))
+              value -= BackwardPawnPenalty[f] / 2;
+      }
+      if (chain)
+          value += ChainBonus[f];
+
+      if (candidate)
+          value += CandidateBonus[relative_rank(Us, s)];
+  }
+
+  return value;
+}
+
+
 /// PawnInfo::updateShelter calculates and caches king shelter. It is called
 /// only when king square changes, about 20% of total get_king_shelter() calls.
 int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) {

src/pawns.h

@@ -47,8 +47,7 @@ class PawnInfo {
 public:
   PawnInfo() { clear(); }
 
-  Value mg_value() const;
-  Value eg_value() const;
+  Score pawns_value() const;
   Value kingside_storm_value(Color c) const;
   Value queenside_storm_value(Color c) const;
   Bitboard pawn_attacks(Color c) const;
@@ -65,7 +64,7 @@ private:
   Key key;
   Bitboard passedPawns;
   Bitboard pawnAttacks[2];
-  int16_t mgValue, egValue;
+  Score value;
   int16_t ksStormValue[2], qsStormValue[2];
   uint8_t halfOpenFiles[2];
   Square kingSquares[2];
@@ -85,6 +84,9 @@ public:
   PawnInfo* get_pawn_info(const Position& pos);
 
 private:
+  template<Color Us>
+  Score evaluate_pawns(const Position& pos, Bitboard ourPawns, Bitboard theirPawns, PawnInfo* pi);
+
   unsigned size;
   PawnInfo* entries;
 };
@@ -94,12 +96,8 @@ private:
 //// Inline functions
 ////
 
-inline Value PawnInfo::mg_value() const {
-  return Value(mgValue);
-}
-
-inline Value PawnInfo::eg_value() const {
-  return Value(egValue);
+inline Score PawnInfo::pawns_value() const {
+  return value;
 }
 
 inline Bitboard PawnInfo::passed_pawns() const {

src/position.cpp

@@ -51,18 +51,31 @@ Key Position::zobEp[64];
 Key Position::zobCastle[16];
 Key Position::zobMaterial[2][8][16];
 Key Position::zobSideToMove;
+Key Position::zobExclusion;
 
-Value Position::MgPieceSquareTable[16][64];
-Value Position::EgPieceSquareTable[16][64];
+Score Position::PieceSquareTable[16][64];
 
 static bool RequestPending = false;
 
-////
-//// Functions
-////
 
 /// Constructors
 
+CheckInfo::CheckInfo(const Position& pos) {
+
+  Color us = pos.side_to_move();
+  Color them = opposite_color(us);
+
+  ksq = pos.king_square(them);
+  dcCandidates = pos.discovered_check_candidates(us);
+
+  checkSq[PAWN] = pos.attacks_from<PAWN>(ksq, them);
+  checkSq[KNIGHT] = pos.attacks_from<KNIGHT>(ksq);
+  checkSq[BISHOP] = pos.attacks_from<BISHOP>(ksq);
+  checkSq[ROOK] = pos.attacks_from<ROOK>(ksq);
+  checkSq[QUEEN] = checkSq[BISHOP] | checkSq[ROOK];
+  checkSq[KING] = EmptyBoardBB;
+}
+
 Position::Position(const Position& pos) {
   copy(pos);
 }
@@ -213,8 +226,7 @@ void Position::from_fen(const string& fen) {
   st->key = compute_key();
   st->pawnKey = compute_pawn_key();
   st->materialKey = compute_material_key();
-  st->mgValue = compute_value<MidGame>();
-  st->egValue = compute_value<EndGame>();
+  st->value = compute_value();
   st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
   st->npMaterial[BLACK] = compute_non_pawn_material(BLACK);
 }
@@ -332,16 +344,15 @@ void Position::copy(const Position& pos) {
 template<bool FindPinned>
 Bitboard Position::hidden_checkers(Color c) const {
 
-  Bitboard pinners, result = EmptyBoardBB;
+  Bitboard result = EmptyBoardBB;
+  Bitboard pinners = pieces_of_color(FindPinned ? opposite_color(c) : c);
 
   // Pinned pieces protect our king, dicovery checks attack
   // the enemy king.
   Square ksq = king_square(FindPinned ? c : opposite_color(c));
 
-  // Pinners are sliders, not checkers, that give check when
-  // candidate pinned is removed.
-  pinners =  (pieces(ROOK, QUEEN, FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq])
-           | (pieces(BISHOP, QUEEN, FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq]);
+  // Pinners are sliders, not checkers, that give check when candidate pinned is removed
+  pinners &= (pieces(ROOK, QUEEN) & RookPseudoAttacks[ksq]) | (pieces(BISHOP, QUEEN) & BishopPseudoAttacks[ksq]);
 
   if (FindPinned && pinners)
       pinners &= ~st->checkersBB;
@@ -458,19 +469,11 @@ void Position::find_checkers() {
 
 /// Position::pl_move_is_legal() tests whether a pseudo-legal move is legal
 
-bool Position::pl_move_is_legal(Move m) const {
-
-  // If we're in check, all pseudo-legal moves are legal, because our
-  // check evasion generator only generates true legal moves.
-  return is_check() || pl_move_is_legal(m, pinned_pieces(side_to_move()));
-}
-
 bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
 
   assert(is_ok());
   assert(move_is_ok(m));
   assert(pinned == pinned_pieces(side_to_move()));
-  assert(!is_check());
 
   // Castling moves are checked for legality during move generation.
   if (move_is_castle(m))
@@ -482,7 +485,7 @@ bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
   assert(color_of_piece_on(from) == us);
   assert(piece_on(king_square(us)) == piece_of_color_and_type(us, KING));
 
-  // En passant captures are a tricky special case.  Because they are
+  // En passant captures are a tricky special case. Because they are
   // rather uncommon, we do it simply by testing whether the king is attacked
   // after the move is made
   if (move_is_ep(m))
@@ -519,179 +522,142 @@ bool Position::pl_move_is_legal(Move m, Bitboard pinned) const {
 }
 
 
+/// Position::pl_move_is_evasion() tests whether a pseudo-legal move is a legal evasion
+
+bool Position::pl_move_is_evasion(Move m, Bitboard pinned) const
+{
+  assert(is_check());
+
+  Color us = side_to_move();
+  Square from = move_from(m);
+  Square to = move_to(m);
+
+  // King moves and en-passant captures are verified in pl_move_is_legal()
+  if (type_of_piece_on(from) == KING || move_is_ep(m))
+      return pl_move_is_legal(m, pinned);
+
+  Bitboard target = checkers();
+  Square checksq = pop_1st_bit(&target);
+
+  if (target) // double check ?
+      return false;
+
+  // Our move must be a blocking evasion or a capture of the checking piece
+  target = squares_between(checksq, king_square(us)) | checkers();
+  return bit_is_set(target, to) && pl_move_is_legal(m, pinned);
+}
+
+
 /// Position::move_is_check() tests whether a pseudo-legal move is a check
 
 bool Position::move_is_check(Move m) const {
 
-  Bitboard dc = discovered_check_candidates(side_to_move());
-  return move_is_check(m, dc);
+  return move_is_check(m, CheckInfo(*this));
 }
 
-bool Position::move_is_check(Move m, Bitboard dcCandidates) const {
+bool Position::move_is_check(Move m, const CheckInfo& ci) const {
 
   assert(is_ok());
   assert(move_is_ok(m));
-  assert(dcCandidates == discovered_check_candidates(side_to_move()));
+  assert(ci.dcCandidates == discovered_check_candidates(side_to_move()));
+  assert(color_of_piece_on(move_from(m)) == side_to_move());
+  assert(piece_on(ci.ksq) == piece_of_color_and_type(opposite_color(side_to_move()), KING));
 
-  Color us = side_to_move();
-  Color them = opposite_color(us);
   Square from = move_from(m);
   Square to = move_to(m);
-  Square ksq = king_square(them);
+  PieceType pt = type_of_piece_on(from);
 
-  assert(color_of_piece_on(from) == us);
-  assert(piece_on(ksq) == piece_of_color_and_type(them, KING));
+  // Direct check ?
+  if (bit_is_set(ci.checkSq[pt], to))
+      return true;
 
-  // Proceed according to the type of the moving piece
-  switch (type_of_piece_on(from))
+  // Discovery check ?
+  if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
   {
-  case PAWN:
-
-      if (bit_is_set(attacks_from<PAWN>(ksq, them), to)) // Normal check?
+      // For pawn and king moves we need to verify also direction
+      if (  (pt != PAWN && pt != KING)
+          ||(direction_between_squares(from, ci.ksq) != direction_between_squares(to, ci.ksq)))
           return true;
-
-      if (   dcCandidates // Discovered check?
-          && bit_is_set(dcCandidates, from)
-          && (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
-          return true;
-
-      if (move_is_promotion(m)) // Promotion with check?
-      {
-          Bitboard b = occupied_squares();
-          clear_bit(&b, from);
-
-          switch (move_promotion_piece(m))
-          {
-          case KNIGHT:
-              return bit_is_set(attacks_from<KNIGHT>(to), ksq);
-          case BISHOP:
-              return bit_is_set(bishop_attacks_bb(to, b), ksq);
-          case ROOK:
-              return bit_is_set(rook_attacks_bb(to, b), ksq);
-          case QUEEN:
-              return bit_is_set(queen_attacks_bb(to, b), ksq);
-          default:
-              assert(false);
-          }
-      }
-      // En passant capture with check?  We have already handled the case
-      // of direct checks and ordinary discovered check, the only case we
-      // need to handle is the unusual case of a discovered check through the
-      // captured pawn.
-      else if (move_is_ep(m))
-      {
-          Square capsq = make_square(square_file(to), square_rank(from));
-          Bitboard b = occupied_squares();
-          clear_bit(&b, from);
-          clear_bit(&b, capsq);
-          set_bit(&b, to);
-          return  (rook_attacks_bb(ksq, b) & pieces(ROOK, QUEEN, us))
-                ||(bishop_attacks_bb(ksq, b) & pieces(BISHOP, QUEEN, us));
-      }
-      return false;
-
-  // Test discovered check and normal check according to piece type
-  case KNIGHT:
-    return   (dcCandidates && bit_is_set(dcCandidates, from))
-          || bit_is_set(attacks_from<KNIGHT>(ksq), to);
-
-  case BISHOP:
-    return   (dcCandidates && bit_is_set(dcCandidates, from))
-          || (direction_is_diagonal(ksq, to) && bit_is_set(attacks_from<BISHOP>(ksq), to));
-
-  case ROOK:
-    return   (dcCandidates && bit_is_set(dcCandidates, from))
-          || (direction_is_straight(ksq, to) && bit_is_set(attacks_from<ROOK>(ksq), to));
-
-  case QUEEN:
-      // Discovered checks are impossible!
-      assert(!bit_is_set(dcCandidates, from));
-      return (   (direction_is_straight(ksq, to) && bit_is_set(attacks_from<ROOK>(ksq), to))
-              || (direction_is_diagonal(ksq, to) && bit_is_set(attacks_from<BISHOP>(ksq), to)));
-
-  case KING:
-      // Discovered check?
-      if (   bit_is_set(dcCandidates, from)
-          && (direction_between_squares(from, ksq) != direction_between_squares(to, ksq)))
-          return true;
-
-      // Castling with check?
-      if (move_is_castle(m))
-      {
-          Square kfrom, kto, rfrom, rto;
-          Bitboard b = occupied_squares();
-          kfrom = from;
-          rfrom = to;
-
-          if (rfrom > kfrom)
-          {
-              kto = relative_square(us, SQ_G1);
-              rto = relative_square(us, SQ_F1);
-          } else {
-              kto = relative_square(us, SQ_C1);
-              rto = relative_square(us, SQ_D1);
-          }
-          clear_bit(&b, kfrom);
-          clear_bit(&b, rfrom);
-          set_bit(&b, rto);
-          set_bit(&b, kto);
-          return bit_is_set(rook_attacks_bb(rto, b), ksq);
-      }
-      return false;
-
-  default: // NO_PIECE_TYPE
-      break;
   }
-  assert(false);
+
+  // Can we skip the ugly special cases ?
+  if (!move_is_special(m))
+      return false;
+
+  Color us = side_to_move();
+  Bitboard b = occupied_squares();
+
+  // Promotion with check ?
+  if (move_is_promotion(m))
+  {
+      clear_bit(&b, from);
+
+      switch (move_promotion_piece(m))
+      {
+      case KNIGHT:
+          return bit_is_set(attacks_from<KNIGHT>(to), ci.ksq);
+      case BISHOP:
+          return bit_is_set(bishop_attacks_bb(to, b), ci.ksq);
+      case ROOK:
+          return bit_is_set(rook_attacks_bb(to, b), ci.ksq);
+      case QUEEN:
+          return bit_is_set(queen_attacks_bb(to, b), ci.ksq);
+      default:
+          assert(false);
+      }
+  }
+
+  // En passant capture with check?  We have already handled the case
+  // of direct checks and ordinary discovered check, the only case we
+  // need to handle is the unusual case of a discovered check through the
+  // captured pawn.
+  if (move_is_ep(m))
+  {
+      Square capsq = make_square(square_file(to), square_rank(from));
+      clear_bit(&b, from);
+      clear_bit(&b, capsq);
+      set_bit(&b, to);
+      return  (rook_attacks_bb(ci.ksq, b) & pieces(ROOK, QUEEN, us))
+            ||(bishop_attacks_bb(ci.ksq, b) & pieces(BISHOP, QUEEN, us));
+  }
+
+  // Castling with check ?
+  if (move_is_castle(m))
+  {
+      Square kfrom, kto, rfrom, rto;
+      kfrom = from;
+      rfrom = to;
+
+      if (rfrom > kfrom)
+      {
+          kto = relative_square(us, SQ_G1);
+          rto = relative_square(us, SQ_F1);
+      } else {
+          kto = relative_square(us, SQ_C1);
+          rto = relative_square(us, SQ_D1);
+      }
+      clear_bit(&b, kfrom);
+      clear_bit(&b, rfrom);
+      set_bit(&b, rto);
+      set_bit(&b, kto);
+      return bit_is_set(rook_attacks_bb(rto, b), ci.ksq);
+  }
+
   return false;
 }
 
 
-/// Position::update_checkers() udpates chekers info given the move. It is called
-/// in do_move() and is faster then find_checkers().
-
-template<PieceType Piece>
-inline void Position::update_checkers(Bitboard* pCheckersBB, Square ksq, Square from,
-                                      Square to, Bitboard dcCandidates) {
-
-  const bool Bishop = (Piece == QUEEN || Piece == BISHOP);
-  const bool Rook   = (Piece == QUEEN || Piece == ROOK);
-  const bool Slider = Bishop || Rook;
-
-  // Direct checks
-  if (  (   (Bishop && bit_is_set(BishopPseudoAttacks[ksq], to))
-         || (Rook   && bit_is_set(RookPseudoAttacks[ksq], to)))
-      && bit_is_set(attacks_from<Piece>(ksq), to)) // slow, try to early skip
-      set_bit(pCheckersBB, to);
-
-  else if (   Piece != KING
-           && !Slider
-           && bit_is_set(Piece == PAWN ? attacks_from<PAWN>(ksq, opposite_color(sideToMove))
-                                       : attacks_from<Piece>(ksq), to))
-      set_bit(pCheckersBB, to);
-
-  // Discovery checks
-  if (Piece != QUEEN && bit_is_set(dcCandidates, from))
-  {
-      if (Piece != ROOK)
-          (*pCheckersBB) |= (attacks_from<ROOK>(ksq) & pieces(ROOK, QUEEN, side_to_move()));
-
-      if (Piece != BISHOP)
-          (*pCheckersBB) |= (attacks_from<BISHOP>(ksq) & pieces(BISHOP, QUEEN, side_to_move()));
-  }
-}
-
-
 /// Position::do_move() makes a move, and saves all information necessary
 /// to a StateInfo object. The move is assumed to be legal.
 /// Pseudo-legal moves should be filtered out before this function is called.
 
 void Position::do_move(Move m, StateInfo& newSt) {
 
-  do_move(m, newSt, discovered_check_candidates(side_to_move()));
+  CheckInfo ci(*this);
+  do_move(m, newSt, ci, move_is_check(m, ci));
 }
 
-void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
+void Position::do_move(Move m, StateInfo& newSt, const CheckInfo& ci, bool moveIsCheck) {
 
   assert(is_ok());
   assert(move_is_ok(m));
@@ -702,10 +668,10 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
   // ones which are recalculated from scratch anyway, then switch our state
   // pointer to point to the new, ready to be updated, state.
   struct ReducedStateInfo {
-    Key key, pawnKey, materialKey;
-    int castleRights, rule50;
+    Key pawnKey, materialKey;
+    int castleRights, rule50, pliesFromNull;
     Square epSquare;
-    Value mgValue, egValue;
+    Score value;
     Value npMaterial[2];
   };
 
@@ -724,6 +690,7 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
   // Increment the 50 moves rule draw counter. Resetting it to zero in the
   // case of non-reversible moves is taken care of later.
   st->rule50++;
+  st->pliesFromNull++;
 
   if (move_is_castle(m))
   {
@@ -741,16 +708,15 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
 
   Piece piece = piece_on(from);
   PieceType pt = type_of_piece(piece);
+  PieceType capture = ep ? PAWN : type_of_piece_on(to);
 
   assert(color_of_piece_on(from) == us);
   assert(color_of_piece_on(to) == them || square_is_empty(to));
   assert(!(ep || pm) || piece == piece_of_color_and_type(us, PAWN));
   assert(!pm || relative_rank(us, to) == RANK_8);
 
-  st->capture = ep ? PAWN : type_of_piece_on(to);
-
-  if (st->capture)
-      do_capture_move(key, st->capture, them, to, ep);
+  if (capture)
+      do_capture_move(key, capture, them, to, ep);
 
   // Update hash key
   key ^= zobrist[us][pt][from] ^ zobrist[us][pt][to];
@@ -800,7 +766,7 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
       st->pawnKey ^= zobrist[us][PAWN][from] ^ zobrist[us][PAWN][to];
 
       // Set en passant square, only if moved pawn can be captured
-      if (abs(int(to) - int(from)) == 16)
+      if ((to ^ from) == 16)
       {
           if (attacks_from<PAWN>(from + (us == WHITE ? DELTA_N : DELTA_S), us) & pieces(PAWN, them))
           {
@@ -811,8 +777,10 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
   }
 
   // Update incremental scores
-  st->mgValue += pst_delta<MidGame>(piece, from, to);
-  st->egValue += pst_delta<EndGame>(piece, from, to);
+  st->value += pst_delta(piece, from, to);
+
+  // Set capture piece
+  st->capture = capture;
 
   if (pm) // promotion ?
   {
@@ -847,10 +815,8 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
       st->pawnKey ^= zobrist[us][PAWN][to];
 
       // Partially revert and update incremental scores
-      st->mgValue -= pst<MidGame>(us, PAWN, to);
-      st->mgValue += pst<MidGame>(us, promotion, to);
-      st->egValue -= pst<EndGame>(us, PAWN, to);
-      st->egValue += pst<EndGame>(us, promotion, to);
+      st->value -= pst(us, PAWN, to);
+      st->value += pst(us, promotion, to);
 
       // Update material
       st->npMaterial[us] += piece_value_midgame(promotion);
@@ -860,29 +826,33 @@ void Position::do_move(Move m, StateInfo& newSt, Bitboard dcCandidates) {
   st->key = key;
 
   // Update checkers bitboard, piece must be already moved
-  if (ep | pm)
-      st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
-  else
+  st->checkersBB = EmptyBoardBB;
+
+  if (moveIsCheck)
   {
-      st->checkersBB = EmptyBoardBB;
-      Square ksq = king_square(them);
-      switch (pt)
+      if (ep | pm)
+          st->checkersBB = attackers_to(king_square(them)) & pieces_of_color(us);
+      else
       {
-      case PAWN:   update_checkers<PAWN>(&(st->checkersBB), ksq, from, to, dcCandidates);   break;
-      case KNIGHT: update_checkers<KNIGHT>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
-      case BISHOP: update_checkers<BISHOP>(&(st->checkersBB), ksq, from, to, dcCandidates); break;
-      case ROOK:   update_checkers<ROOK>(&(st->checkersBB), ksq, from, to, dcCandidates);   break;
-      case QUEEN:  update_checkers<QUEEN>(&(st->checkersBB), ksq, from, to, dcCandidates);  break;
-      case KING:   update_checkers<KING>(&(st->checkersBB), ksq, from, to, dcCandidates);   break;
-      default: assert(false); break;
+          // Direct checks
+          if (bit_is_set(ci.checkSq[pt], to))
+              st->checkersBB = SetMaskBB[to];
+
+          // Discovery checks
+          if (ci.dcCandidates && bit_is_set(ci.dcCandidates, from))
+          {
+              if (pt != ROOK)
+                  st->checkersBB |= (attacks_from<ROOK>(ci.ksq) & pieces(ROOK, QUEEN, us));
+
+              if (pt != BISHOP)
+                  st->checkersBB |= (attacks_from<BISHOP>(ci.ksq) & pieces(BISHOP, QUEEN, us));
+          }
       }
   }
 
   // Finish
   sideToMove = opposite_color(sideToMove);
-
-  st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
-  st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
+  st->value += (sideToMove == WHITE ?  TempoValue : -TempoValue);
 
   assert(is_ok());
 }
@@ -918,8 +888,7 @@ void Position::do_capture_move(Bitboard& key, PieceType capture, Color them, Squ
     key ^= zobrist[them][capture][capsq];
 
     // Update incremental scores
-    st->mgValue -= pst<MidGame>(them, capture, capsq);
-    st->egValue -= pst<EndGame>(them, capture, capsq);
+    st->value -= pst(them, capture, capsq);
 
     // If the captured piece was a pawn, update pawn hash key,
     // otherwise update non-pawn material.
@@ -1000,7 +969,7 @@ void Position::do_castle_move(Move m) {
   set_bit(&(byColorBB[us]), rto);
   set_bit(&(byTypeBB[ROOK]), rto);
   set_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
-  
+
   // Update board array
   Piece king = piece_of_color_and_type(us, KING);
   Piece rook = piece_of_color_and_type(us, ROOK);
@@ -1016,10 +985,8 @@ void Position::do_castle_move(Move m) {
   index[rto] = tmp;
 
   // Update incremental scores
-  st->mgValue += pst_delta<MidGame>(king, kfrom, kto);
-  st->egValue += pst_delta<EndGame>(king, kfrom, kto);
-  st->mgValue += pst_delta<MidGame>(rook, rfrom, rto);
-  st->egValue += pst_delta<EndGame>(rook, rfrom, rto);
+  st->value += pst_delta(king, kfrom, kto);
+  st->value += pst_delta(rook, rfrom, rto);
 
   // Update hash key
   st->key ^= zobrist[us][KING][kfrom] ^ zobrist[us][KING][kto];
@@ -1045,9 +1012,7 @@ void Position::do_castle_move(Move m) {
 
   // Finish
   sideToMove = opposite_color(sideToMove);
-
-  st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
-  st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
+  st->value += (sideToMove == WHITE ?  TempoValue : -TempoValue);
 
   assert(is_ok());
 }
@@ -1189,7 +1154,7 @@ void Position::undo_castle_move(Move m) {
 
   assert(piece_on(kto) == piece_of_color_and_type(us, KING));
   assert(piece_on(rto) == piece_of_color_and_type(us, ROOK));
-  
+
   // Remove pieces from destination squares:
   clear_bit(&(byColorBB[us]), kto);
   clear_bit(&(byTypeBB[KING]), kto);
@@ -1197,7 +1162,7 @@ void Position::undo_castle_move(Move m) {
   clear_bit(&(byColorBB[us]), rto);
   clear_bit(&(byTypeBB[ROOK]), rto);
   clear_bit(&(byTypeBB[0]), rto); // HACK: byTypeBB[0] == occupied squares
- 
+
   // Put pieces on source squares:
   set_bit(&(byColorBB[us]), kfrom);
   set_bit(&(byTypeBB[KING]), kfrom);
@@ -1239,9 +1204,9 @@ void Position::do_null_move(StateInfo& backupSt) {
   // a backup storage not as a new state to be used.
   backupSt.key      = st->key;
   backupSt.epSquare = st->epSquare;
-  backupSt.mgValue  = st->mgValue;
-  backupSt.egValue  = st->egValue;
+  backupSt.value    = st->value;
   backupSt.previous = st->previous;
+  backupSt.pliesFromNull = st->pliesFromNull;
   st->previous = &backupSt;
 
   // Save the current key to the history[] array, in order to be able to
@@ -1258,10 +1223,9 @@ void Position::do_null_move(StateInfo& backupSt) {
   sideToMove = opposite_color(sideToMove);
   st->epSquare = SQ_NONE;
   st->rule50++;
+  st->pliesFromNull = 0;
+  st->value += (sideToMove == WHITE) ?  TempoValue : -TempoValue;
   gamePly++;
-
-  st->mgValue += (sideToMove == WHITE)? TempoValueMidgame : -TempoValueMidgame;
-  st->egValue += (sideToMove == WHITE)? TempoValueEndgame : -TempoValueEndgame;
 }
 
 
@@ -1276,9 +1240,9 @@ void Position::undo_null_move() {
   StateInfo* backupSt = st->previous;
   st->key      = backupSt->key;
   st->epSquare = backupSt->epSquare;
-  st->mgValue  = backupSt->mgValue;
-  st->egValue  = backupSt->egValue;
+  st->value    = backupSt->value;
   st->previous = backupSt->previous;
+  st->pliesFromNull = backupSt->pliesFromNull;
 
   // Update the necessary information
   sideToMove = opposite_color(sideToMove);
@@ -1346,6 +1310,10 @@ int Position::see(Square from, Square to) const {
   Piece capture = piece_on(to);
   Bitboard occ = occupied_squares();
 
+  // King cannot be recaptured
+  if (type_of_piece(piece) == KING)
+      return seeValues[capture];
+
   // Handle en passant moves
   if (st->epSquare == to && type_of_piece_on(from) == PAWN)
   {
@@ -1484,8 +1452,8 @@ void Position::clear() {
   for (int i = 0; i < 64; i++)
       board[i] = EMPTY;
 
-  for (int i = 0; i < 7; i++)
-      for (int j = 0; j < 8; j++)
+  for (int i = 0; i < 8; i++)
+      for (int j = 0; j < 16; j++)
           pieceList[0][i][j] = pieceList[1][i][j] = SQ_NONE;
 
   sideToMove = WHITE;
@@ -1619,10 +1587,9 @@ Key Position::compute_material_key() const {
 /// game and the endgame. These functions are used to initialize the incremental
 /// scores when a new position is set up, and to verify that the scores are correctly
 /// updated by do_move and undo_move when the program is running in debug mode.
-template<Position::GamePhase Phase>
-Value Position::compute_value() const {
+Score Position::compute_value() const {
 
-  Value result = Value(0);
+  Score result = make_score(0, 0);
   Bitboard b;
   Square s;
 
@@ -1634,12 +1601,11 @@ Value Position::compute_value() const {
           {
               s = pop_1st_bit(&b);
               assert(piece_on(s) == piece_of_color_and_type(c, pt));
-              result += pst<Phase>(c, pt, s);
+              result += pst(c, pt, s);
           }
       }
 
-  const Value TempoValue = (Phase == MidGame ? TempoValueMidgame : TempoValueEndgame);
-  result += (side_to_move() == WHITE)? TempoValue / 2 : -TempoValue / 2;
+  result += (side_to_move() == WHITE ? TempoValue / 2 : -TempoValue / 2);
   return result;
 }
 
@@ -1683,7 +1649,7 @@ bool Position::is_draw() const {
       return true;
 
   // Draw by repetition?
-  for (int i = 2; i < Min(gamePly, st->rule50); i += 2)
+  for (int i = 2; i < Min(Min(gamePly, st->rule50), st->pliesFromNull); i += 2)
       if (history[gamePly - i] == st->key)
           return true;
 
@@ -1697,8 +1663,7 @@ bool Position::is_draw() const {
 bool Position::is_mate() const {
 
   MoveStack moves[256];
-
-  return is_check() && (generate_evasions(*this, moves, pinned_pieces(sideToMove)) == moves);
+  return is_check() && (generate_moves(*this, moves, false) == moves);
 }
 
 
@@ -1719,11 +1684,10 @@ bool Position::has_mate_threat(Color c) {
 
   MoveStack mlist[120];
   bool result = false;
-  Bitboard dc = discovered_check_candidates(sideToMove);
   Bitboard pinned = pinned_pieces(sideToMove);
 
   // Generate pseudo-legal non-capture and capture check moves
-  MoveStack* last = generate_non_capture_checks(*this, mlist, dc);
+  MoveStack* last = generate_non_capture_checks(*this, mlist);
   last = generate_captures(*this, last);
 
   // Loop through the moves, and see if one of them is mate
@@ -1773,6 +1737,8 @@ void Position::init_zobrist() {
 
   for (int i = 0; i < 16; i++)
       zobMaterial[0][KING][i] = zobMaterial[1][KING][i] = Key(0ULL);
+
+  zobExclusion = genrand_int64();
 }
 
 
@@ -1790,16 +1756,12 @@ void Position::init_piece_square_tables() {
       for (Piece p = WP; p <= WK; p++)
       {
           i = (r == 0)? 0 : (genrand_int32() % (r*2) - r);
-          MgPieceSquareTable[p][s] = Value(MgPST[p][s] + i);
-          EgPieceSquareTable[p][s] = Value(EgPST[p][s] + i);
+          PieceSquareTable[p][s] = make_score(MgPST[p][s] + i, EgPST[p][s] + i);
       }
 
   for (Square s = SQ_A1; s <= SQ_H8; s++)
       for (Piece p = BP; p <= BK; p++)
-      {
-          MgPieceSquareTable[p][s] = -MgPieceSquareTable[p-8][flip_square(s)];
-          EgPieceSquareTable[p][s] = -EgPieceSquareTable[p-8][flip_square(s)];
-      }
+          PieceSquareTable[p][s] = -PieceSquareTable[p-8][flip_square(s)];
 }
 
 
@@ -1854,8 +1816,7 @@ void Position::flipped_copy(const Position& pos) {
   st->materialKey = compute_material_key();
 
   // Incremental scores
-  st->mgValue = compute_value<MidGame>();
-  st->egValue = compute_value<EndGame>();
+  st->value = compute_value();
 
   // Material
   st->npMaterial[WHITE] = compute_non_pawn_material(WHITE);
@@ -1982,14 +1943,8 @@ bool Position::is_ok(int* failedStep) const {
 
   // Incremental eval OK?
   if (failedStep) (*failedStep)++;
-  if (debugIncrementalEval)
-  {
-      if (st->mgValue != compute_value<MidGame>())
-          return false;
-
-      if (st->egValue != compute_value<EndGame>())
-          return false;
-  }
+  if (debugIncrementalEval && st->value != compute_value())
+      return false;
 
   // Non-pawn material OK?
   if (failedStep) (*failedStep)++;

src/position.h

@@ -63,6 +63,18 @@ const int MaxGameLength = 220;
 //// Types
 ////
 
+/// struct checkInfo is initialized at c'tor time and keeps
+/// info used to detect if a move gives check.
+
+struct CheckInfo {
+
+    CheckInfo(const Position&);
+
+    Square ksq;
+    Bitboard dcCandidates;
+    Bitboard checkSq[8];
+};
+
 /// Castle rights, encoded as bit fields
 
 enum CastleRights {
@@ -87,12 +99,13 @@ enum Phase {
 /// must be passed as a parameter.
 
 struct StateInfo {
-  Key key, pawnKey, materialKey;
-  int castleRights, rule50;
+  Key pawnKey, materialKey;
+  int castleRights, rule50, pliesFromNull;
   Square epSquare;
-  Value mgValue, egValue;
+  Score value;
   Value npMaterial[2];
 
+  Key key;
   PieceType capture;
   Bitboard checkersBB;
   StateInfo* previous;
@@ -202,11 +215,12 @@ public:
   template<PieceType> Bitboard attacks_from(Square s, Color c) const;
 
   // Properties of moves
-  bool pl_move_is_legal(Move m) const;
   bool pl_move_is_legal(Move m, Bitboard pinned) const;
+  bool pl_move_is_evasion(Move m, Bitboard pinned) const;
   bool move_is_check(Move m) const;
-  bool move_is_check(Move m, Bitboard dcCandidates) const;
+  bool move_is_check(Move m, const CheckInfo& ci) const;
   bool move_is_capture(Move m) const;
+  bool move_is_capture_or_promotion(Move m) const;
   bool move_is_passed_pawn_push(Move m) const;
   bool move_attacks_square(Move m, Square s) const;
 
@@ -222,7 +236,7 @@ public:
   // Doing and undoing moves
   void saveState();
   void do_move(Move m, StateInfo& st);
-  void do_move(Move m, StateInfo& st, Bitboard dcCandidates);
+  void do_move(Move m, StateInfo& st, const CheckInfo& ci, bool moveIsCheck);
   void undo_move(Move m);
   void do_null_move(StateInfo& st);
   void undo_null_move();
@@ -235,15 +249,14 @@ public:
 
   // Accessing hash keys
   Key get_key() const;
+  Key get_exclusion_key() const;
   Key get_pawn_key() const;
   Key get_material_key() const;
 
   // Incremental evaluation
-  Value mg_value() const;
-  Value eg_value() const;
+  Score value() const;
   Value non_pawn_material(Color c) const;
-  Phase game_phase() const;
-  template<GamePhase> Value pst_delta(Piece piece, Square from, Square to) const;
+  Score pst_delta(Piece piece, Square from, Square to) const;
 
   // Game termination checks
   bool is_mate() const;
@@ -283,9 +296,6 @@ private:
   void undo_castle_move(Move m);
   void find_checkers();
 
-  template<PieceType Piece>
-  void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
-
   template<bool FindPinned>
   Bitboard hidden_checkers(Color c) const;
 
@@ -295,8 +305,8 @@ private:
   Key compute_material_key() const;
 
   // Computing incremental evaluation scores and material counts
-  template<GamePhase> Value pst(Color c, PieceType pt, Square s) const;
-  template<GamePhase> Value compute_value() const;
+  Score pst(Color c, PieceType pt, Square s) const;
+  Score compute_value() const;
   Value compute_non_pawn_material(Color c) const;
 
   // Board
@@ -327,8 +337,8 @@ private:
   static Key zobCastle[16];
   static Key zobMaterial[2][8][16];
   static Key zobSideToMove;
-  static Value MgPieceSquareTable[16][64];
-  static Value EgPieceSquareTable[16][64];
+  static Score PieceSquareTable[16][64];
+  static Key zobExclusion;
 };
 
 
@@ -493,6 +503,10 @@ inline Key Position::get_key() const {
   return st->key;
 }
 
+inline Key Position::get_exclusion_key() const {
+  return st->key ^ zobExclusion;
+}
+
 inline Key Position::get_pawn_key() const {
   return st->pawnKey;
 }
@@ -501,46 +515,22 @@ inline Key Position::get_material_key() const {
   return st->materialKey;
 }
 
-template<Position::GamePhase Ph>
-inline Value Position::pst(Color c, PieceType pt, Square s) const {
-  return (Ph == MidGame ? MgPieceSquareTable[piece_of_color_and_type(c, pt)][s]
-                        : EgPieceSquareTable[piece_of_color_and_type(c, pt)][s]);
+inline Score Position::pst(Color c, PieceType pt, Square s) const {
+  return PieceSquareTable[piece_of_color_and_type(c, pt)][s];
 }
 
-template<Position::GamePhase Ph>
-inline Value Position::pst_delta(Piece piece, Square from, Square to) const {
-  return (Ph == MidGame ? MgPieceSquareTable[piece][to] - MgPieceSquareTable[piece][from]
-                        : EgPieceSquareTable[piece][to] - EgPieceSquareTable[piece][from]);
+inline Score Position::pst_delta(Piece piece, Square from, Square to) const {
+  return PieceSquareTable[piece][to] - PieceSquareTable[piece][from];
 }
 
-inline Value Position::mg_value() const {
-  return st->mgValue;
-}
-
-inline Value Position::eg_value() const {
-  return st->egValue;
+inline Score Position::value() const {
+  return st->value;
 }
 
 inline Value Position::non_pawn_material(Color c) const {
   return st->npMaterial[c];
 }
 
-inline Phase Position::game_phase() const {
-
-  // Values modified by Joona Kiiski
-  static const Value MidgameLimit = Value(15581);
-  static const Value EndgameLimit = Value(3998);
-
-  Value npm = non_pawn_material(WHITE) + non_pawn_material(BLACK);
-
-  if (npm >= MidgameLimit)
-      return PHASE_MIDGAME;
-  else if(npm <= EndgameLimit)
-      return PHASE_ENDGAME;
-  else
-      return Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
-}
-
 inline bool Position::move_is_passed_pawn_push(Move m) const {
 
   Color c = side_to_move();
@@ -568,8 +558,13 @@ inline bool Position::has_pawn_on_7th(Color c) const {
 inline bool Position::move_is_capture(Move m) const {
 
   // Move must not be MOVE_NONE !
+  return (m & (3 << 15)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
+}
 
-  return (!square_is_empty(move_to(m)) && !move_is_castle(m)) || move_is_ep(m);
+inline bool Position::move_is_capture_or_promotion(Move m) const {
+
+  // Move must not be MOVE_NONE !
+  return (m & (0x1F << 12)) ? !move_is_castle(m) : !square_is_empty(move_to(m));
 }
 
 #endif // !defined(POSITION_H_INCLUDED)

src/san.cpp

@@ -142,13 +142,14 @@ Move move_from_san(const Position& pos, const string& movestr) {
   assert(pos.is_ok());
 
   MovePicker mp = MovePicker(pos, MOVE_NONE, OnePly, H);
+  Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
 
   // Castling moves
   if (movestr == "O-O-O" || movestr == "O-O-O+")
   {
       Move m;
       while ((m = mp.get_next_move()) != MOVE_NONE)
-          if (move_is_long_castle(m) && pos.pl_move_is_legal(m))
+          if (move_is_long_castle(m) && pos.pl_move_is_legal(m, pinned))
               return m;
 
       return MOVE_NONE;
@@ -157,7 +158,7 @@ Move move_from_san(const Position& pos, const string& movestr) {
   {
       Move m;
       while ((m = mp.get_next_move()) != MOVE_NONE)
-          if (move_is_short_castle(m) && pos.pl_move_is_legal(m))
+          if (move_is_short_castle(m) && pos.pl_move_is_legal(m, pinned))
               return m;
 
     return MOVE_NONE;
@@ -367,11 +368,12 @@ namespace {
         return AMBIGUITY_NONE;
 
     MovePicker mp = MovePicker(pos, MOVE_NONE, OnePly, H);
+    Bitboard pinned = pos.pinned_pieces(pos.side_to_move());
     Move mv, moveList[8];
 
     int n = 0;
     while ((mv = mp.get_next_move()) != MOVE_NONE)
-        if (move_to(mv) == to && pos.piece_on(move_from(mv)) == pc && pos.pl_move_is_legal(mv))
+        if (move_to(mv) == to && pos.piece_on(move_from(mv)) == pc && pos.pl_move_is_legal(mv, pinned))
             moveList[n++] = mv;
 
     if (n == 1)

src/search.h

@@ -48,7 +48,7 @@ const int KILLER_MAX = 2;
 /// current ply.
 
 struct SearchStack {
-  Move pv[PLY_MAX];
+  Move pv[PLY_MAX_PLUS_2];
   Move currentMove;
   Move mateKiller;
   Move threatMove;
@@ -69,6 +69,7 @@ extern void stop_threads();
 extern bool think(const Position &pos, bool infinite, bool ponder, int side_to_move,
                   int time[], int increment[], int movesToGo, int maxDepth,
                   int maxNodes, int maxTime, Move searchMoves[]);
+extern int perft(Position &pos, Depth depth);
 extern int64_t nodes_searched();
 
 

src/thread.h

@@ -46,13 +46,13 @@ const int THREAD_MAX = 8;
 struct SplitPoint {
   SplitPoint *parent;
   Position pos;
-  SearchStack sstack[THREAD_MAX][PLY_MAX];
+  SearchStack sstack[THREAD_MAX][PLY_MAX_PLUS_2];
   SearchStack *parentSstack;
   int ply;
   Depth depth;
-  volatile Value alpha, beta, bestValue;
+  volatile Value alpha, beta, bestValue, futilityValue;
+  Value approximateEval;
   bool pvNode;
-  Bitboard dcCandidates;
   int master, slaves[THREAD_MAX];
   Lock lock;
   MovePicker *mp;

src/tt.cpp

@@ -208,7 +208,9 @@ void TranspositionTable::insert_pv(const Position& pos, Move pv[]) {
 
   for (int i = 0; pv[i] != MOVE_NONE; i++)
   {
-      store(p.get_key(), VALUE_NONE, VALUE_TYPE_NONE, Depth(-127*OnePly), pv[i]);
+      TTEntry *tte = retrieve(p.get_key());
+      if (!tte || tte->move() != pv[i])
+          store(p.get_key(), VALUE_NONE, VALUE_TYPE_NONE, Depth(-127*OnePly), pv[i]);
       p.do_move(pv[i], st);
   }
 }
@@ -220,7 +222,7 @@ void TranspositionTable::insert_pv(const Position& pos, Move pv[]) {
 /// will often get single-move PVs when the search stops while failing high,
 /// and a single-move PV means that we don't have a ponder move.
 
-void TranspositionTable::extract_pv(const Position& pos, Move pv[], int pvSize) {
+void TranspositionTable::extract_pv(const Position& pos, Move pv[], const int PLY_MAX) {
 
   const TTEntry* tte;
   StateInfo st;
@@ -236,7 +238,7 @@ void TranspositionTable::extract_pv(const Position& pos, Move pv[], int pvSize)
          && tte->move() != MOVE_NONE
          && move_is_legal(p, tte->move())
          && (!p.is_draw() || ply < 2)
-         && ply < pvSize)
+         && ply < PLY_MAX)
   {
       pv[ply] = tte->move();
       p.do_move(pv[ply++], st);

src/tt.h

@@ -102,7 +102,7 @@ public:
   void prefetch(const Key posKey) const;
   void new_search();
   void insert_pv(const Position& pos, Move pv[]);
-  void extract_pv(const Position& pos, Move pv[], int pvSize);
+  void extract_pv(const Position& pos, Move pv[], const int PLY_MAX);
   int full() const;
 
 private:

src/types.h

@@ -33,7 +33,7 @@ typedef __int16 int16;
 typedef unsigned __int16 uint16_t;
 typedef __int32 int32_t;
 typedef unsigned __int32 uint32_t;
-typedef __int64 int64;
+typedef __int64 int64_t;
 typedef unsigned __int64 uint64_t;
 
 typedef __int16 int16_t;

src/uci.cpp

@@ -61,6 +61,7 @@ namespace {
   void set_option(UCIInputParser& uip);
   void set_position(UCIInputParser& uip);
   bool go(UCIInputParser& uip);
+  void perft(UCIInputParser& uip);
 }
 
 
@@ -123,7 +124,7 @@ namespace {
     }
     else if (token == "ucinewgame")
     {
-        push_button("Clear Hash");
+        push_button("New Game");
         Position::init_piece_square_tables();
         RootPosition.from_fen(StartPosition);
     }
@@ -147,14 +148,16 @@ namespace {
     else if (token == "eval")
     {
         EvalInfo ei;
-        cout << "Incremental mg: " << RootPosition.mg_value()
-             << "\nIncremental eg: " << RootPosition.eg_value()
+        cout << "Incremental mg: " << mg_value(RootPosition.value())
+             << "\nIncremental eg: " << eg_value(RootPosition.value())
              << "\nFull eval: " << evaluate(RootPosition, ei, 0) << endl;
     }
     else if (token == "key")
         cout << "key: " << hex << RootPosition.get_key()
              << "\nmaterial key: " << RootPosition.get_material_key()
              << "\npawn key: " << RootPosition.get_pawn_key() << endl;
+    else if (token == "perft")
+        perft(uip);
     else
     {
         cout << "Unknown command: " << command << endl;
@@ -318,4 +321,23 @@ namespace {
                  time, inc, movesToGo, depth, nodes, moveTime, searchMoves);
   }
 
+  void perft(UCIInputParser& uip) {
+
+    string token;
+    int depth, tm, n;
+    Position pos = RootPosition;
+
+    if (uip.eof())
+        return;
+
+    uip >> depth;
+    tm = get_system_time();
+
+    n = perft(pos, depth * OnePly);
+
+    tm = get_system_time() - tm;
+    std::cout << "\nNodes " << n
+              << "\nTime (ms) " << tm
+              << "\nNodes/second " << (int)(n/(tm/1000.0)) << std::endl;
+  }
 }

src/ucioption.cpp

@@ -125,6 +125,7 @@ namespace {
     o["Threads"] = Option(1, 1, 8);
     o["Hash"] = Option(32, 4, 4096);
     o["Clear Hash"] = Option(false, BUTTON);
+    o["New Game"] = Option(false, BUTTON);
     o["Ponder"] = Option(true);
     o["OwnBook"] = Option(true);
     o["MultiPV"] = Option(1, 1, 500);
@@ -169,6 +170,18 @@ namespace {
       return ret;
   }
 
+  // Specialization for std::string where instruction 'ss >> ret;'
+  // would erroneusly tokenize a string with spaces.
+
+  template<>
+  string get_option_value<string>(const string& optionName) {
+
+      if (options.find(optionName) == options.end())
+          return string();
+
+      return options[optionName].currentValue;
+  }
+
 }
 
 ////

src/value.h

@@ -52,6 +52,32 @@ enum Value {
 };
 
 
+/// Score enum keeps a midgame and an endgame value in a single
+/// integer (enum), first LSB 16 bits are used to store endgame
+/// value, while upper bits are used for midgame value.
+
+enum Score {};
+
+inline Value eg_value(Score s) { return Value(int16_t(s & 0xffff)); }
+inline Value mg_value(Score s) { return Value((int(s) + 32768) >> 16); }
+
+inline Score make_score(int mg, int eg) { return Score((mg << 16) + eg); }
+
+inline Score operator-(Score s) { return Score(-int(s)); }
+inline Score operator+(Score s1, Score s2) { return Score(int(s1) + int(s2)); }
+inline Score operator-(Score s1, Score s2) { return Score(int(s1) - int(s2)); }
+inline void operator+=(Score& s1, Score s2) { s1 = Score(int(s1) + int(s2)); }
+inline void operator-=(Score& s1, Score s2) { s1 = Score(int(s1) - int(s2)); }
+inline Score operator*(int i, Score s) { return Score(i * int(s)); }
+
+// Division must be handled separately for each term
+inline Score operator/(Score s, int i) { return make_score(mg_value(s) / i, eg_value(s) / i); }
+
+// Only declared but not defined. We don't want to multiply two scores due to
+// a very high risk of overflow. So user should explicitly convert to integer.
+inline Score operator*(Score s1, Score s2);
+
+
 ////
 //// Constants and variables
 ////
@@ -97,8 +123,7 @@ const Value PieceValueEndgame[17] = {
 
 /// Bonus for having the side to move (modified by Joona Kiiski)
 
-const Value TempoValueMidgame = Value(48);
-const Value TempoValueEndgame = Value(22);
+const Score TempoValue = make_score(48, 22);
 
 
 ////