Simplify sudden death time optimization

Passed Sudden Death STC:
https://tests.stockfishchess.org/tests/view/68455fe5375c2b77d9855351
LLR: 2.91 (-2.94,2.94) <-1.75,0.25>
Total: 49248 W: 13008 L: 12798 D: 23442
Ptnml(0-2): 309, 5491, 12821, 5687, 316

Passed Sudden Death LTC:
https://tests.stockfishchess.org/tests/view/6845a392375c2b77d98553cf
LLR: 3.01 (-2.94,2.94) <-1.75,0.25>
Total: 551070 W: 141699 L: 142031 D: 267340
Ptnml(0-2): 1923, 60608, 150916, 60054, 2034

Passed Standard STC:
https://tests.stockfishchess.org/tests/view/683c5ebb6ec7634154f9d989
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 142624 W: 36808 L: 36709 D: 69107
Ptnml(0-2): 302, 15448, 39745, 15483, 334

Passed Standard LTC:
https://tests.stockfishchess.org/tests/view/683f1a4f6ec7634154f9dc5a
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 146922 W: 37381 L: 37296 D: 72245
Ptnml(0-2): 69, 13552, 46117, 13671, 52

closes https://github.com/official-stockfish/Stockfish/pull/6132

Bench: 2249459

.github/workflows/tests.yml

@@ -39,14 +39,15 @@ jobs:
             comp: ndk
             run_armv7_tests: true
             shell: bash
-          - name: Linux GCC riscv64
-            os: ubuntu-22.04
-            compiler: g++
-            comp: gcc
-            run_riscv64_tests: true
-            base_image: "riscv64/alpine:edge"
-            platform: linux/riscv64
-            shell: bash
+          # Currently segfaults in the CI unrelated to a Stockfish change.
+          # - name: Linux GCC riscv64
+          #   os: ubuntu-22.04
+          #   compiler: g++
+          #   comp: gcc
+          #   run_riscv64_tests: true
+          #   base_image: "riscv64/alpine:edge"
+          #   platform: linux/riscv64
+          #   shell: bash
           - name: Linux GCC ppc64
             os: ubuntu-22.04
             compiler: g++

src/Makefile

@@ -701,7 +701,7 @@ endif
 ifeq ($(avx512),yes)
 	CXXFLAGS += -DUSE_AVX512
 	ifeq ($(comp),$(filter $(comp),gcc clang mingw icx))
-		CXXFLAGS += -mavx512f -mavx512bw
+		CXXFLAGS += -mavx512f -mavx512bw -mavx512dq -mavx512vl
 	endif
 endif
 
@@ -996,10 +996,6 @@ net:
 format:
 	$(CLANG-FORMAT) -i $(SRCS) $(HEADERS) -style=file
 
-# default target
-default:
-	help
-
 ### ==========================================================================
 ### Section 5. Private Targets
 ### ==========================================================================
@@ -1125,6 +1121,6 @@ icx-profile-use:
 .depend: $(SRCS)
 	-@$(CXX) $(DEPENDFLAGS) -MM $(SRCS) > $@ 2> /dev/null
 
-ifeq (, $(filter $(MAKECMDGOALS), help strip install clean net objclean profileclean config-sanity))
+ifeq (, $(filter $(MAKECMDGOALS), help strip install clean net objclean profileclean format config-sanity))
 -include .depend
 endif

src/movepick.cpp

@@ -56,6 +56,7 @@ enum Stages {
     QCAPTURE
 };
 
+
 // Sort moves in descending order up to and including a given limit.
 // The order of moves smaller than the limit is left unspecified.
 void partial_insertion_sort(ExtMove* begin, ExtMove* end, int limit) {
@@ -207,6 +208,7 @@ Move MovePicker::select(Pred filter) {
 // picking the move with the highest score from a list of generated moves.
 Move MovePicker::next_move() {
 
+    constexpr int goodQuietThreshold = -14000;
 top:
     switch (stage)
     {
@@ -222,7 +224,7 @@ top:
     case PROBCUT_INIT :
     case QCAPTURE_INIT :
         cur = endBadCaptures = moves;
-        endCur               = generate<CAPTURES>(pos, cur);
+        endCur = endCaptures = generate<CAPTURES>(pos, cur);
 
         score<CAPTURES>();
         partial_insertion_sort(cur, endCur, std::numeric_limits<int>::min());
@@ -244,8 +246,7 @@ top:
     case QUIET_INIT :
         if (!skipQuiets)
         {
-            cur = endBadQuiets = endBadCaptures;
-            endCur             = generate<QUIETS>(pos, cur);
+            endCur = endGenerated = generate<QUIETS>(pos, cur);
 
             score<QUIETS>();
             partial_insertion_sort(cur, endCur, -3560 * depth);
@@ -255,12 +256,7 @@ top:
         [[fallthrough]];
 
     case GOOD_QUIET :
-        if (!skipQuiets && select([&]() {
-                if (cur->value > -14000)
-                    return true;
-                *endBadQuiets++ = *cur;
-                return false;
-            }))
+        if (!skipQuiets && select([&]() { return cur->value > goodQuietThreshold; }))
             return *(cur - 1);
 
         // Prepare the pointers to loop over the bad captures
@@ -274,22 +270,22 @@ top:
         if (select([]() { return true; }))
             return *(cur - 1);
 
-        // Prepare the pointers to loop over the bad quiets
-        cur    = endBadCaptures;
-        endCur = endBadQuiets;
+        // Prepare the pointers to loop over quiets again
+        cur    = endCaptures;
+        endCur = endGenerated;
 
         ++stage;
         [[fallthrough]];
 
     case BAD_QUIET :
         if (!skipQuiets)
-            return select([]() { return true; });
+            return select([&]() { return cur->value <= goodQuietThreshold; });
 
         return Move::none();
 
     case EVASION_INIT :
         cur    = moves;
-        endCur = generate<EVASIONS>(pos, cur);
+        endCur = endGenerated = generate<EVASIONS>(pos, cur);
 
         score<EVASIONS>();
         partial_insertion_sort(cur, endCur, std::numeric_limits<int>::min());
@@ -315,7 +311,7 @@ bool MovePicker::can_move_king_or_pawn() const {
     // SEE negative captures shouldn't be returned in GOOD_CAPTURE stage
     assert(stage > GOOD_CAPTURE && stage != EVASION_INIT);
 
-    for (const ExtMove* m = moves; m < endCur; ++m)
+    for (const ExtMove* m = moves; m < endGenerated; ++m)
     {
         PieceType movedPieceType = type_of(pos.moved_piece(*m));
         if ((movedPieceType == PAWN || movedPieceType == KING) && pos.legal(*m))

src/movepick.h

@@ -67,7 +67,7 @@ class MovePicker {
     const PieceToHistory**       continuationHistory;
     const PawnHistory*           pawnHistory;
     Move                         ttMove;
-    ExtMove *                    cur, *endCur, *endBadCaptures, *endBadQuiets;
+    ExtMove *                    cur, *endCur, *endBadCaptures, *endCaptures, *endGenerated;
     int                          stage;
     int                          threshold;
     Depth                        depth;

src/nnue/layers/affine_transform_sparse_input.h

@@ -68,9 +68,42 @@ alignas(CacheLineSize) static constexpr struct OffsetIndices {
 
 } Lookup;
 
+    #if defined(__GNUC__) || defined(__clang__)
+        #define RESTRICT __restrict__
+    #elif defined(_MSC_VER)
+        #define RESTRICT __restrict
+    #else
+        #define RESTRICT
+    #endif
+
 // Find indices of nonzero numbers in an int32_t array
 template<const IndexType InputDimensions>
-void find_nnz(const std::int32_t* input, std::uint16_t* out, IndexType& count_out) {
+void find_nnz(const std::int32_t* RESTRICT input,
+              std::uint16_t* RESTRICT      out,
+              IndexType&                   count_out) {
+
+    #ifdef USE_AVX512
+    constexpr IndexType SimdWidth = 16;  // 512 bits / 32 bits
+    constexpr IndexType NumChunks = InputDimensions / SimdWidth;
+    const __m512i       increment = _mm512_set1_epi32(SimdWidth);
+    __m512i base = _mm512_set_epi32(15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0);
+
+    IndexType count = 0;
+    for (IndexType i = 0; i < NumChunks; ++i)
+    {
+        const __m512i inputV = _mm512_load_si512(input + i * SimdWidth);
+
+        // Get a bitmask and gather non zero indices
+        const __mmask16 nnzMask = _mm512_test_epi32_mask(inputV, inputV);
+        const __m512i   nnzV    = _mm512_maskz_compress_epi32(nnzMask, base);
+        _mm512_mask_cvtepi32_storeu_epi16(out + count, 0xFFFF, nnzV);
+        count += popcount(nnzMask);
+        base = _mm512_add_epi32(base, increment);
+    }
+    count_out = count;
+
+    #else
+
     using namespace SIMD;
 
     constexpr IndexType InputSimdWidth = sizeof(vec_uint_t) / sizeof(std::int32_t);
@@ -104,6 +137,7 @@ void find_nnz(const std::int32_t* input, std::uint16_t* out, IndexType& count_ou
         }
     }
     count_out = count;
+    #endif
 }
 
 #endif

src/search.cpp

@@ -63,6 +63,9 @@ using namespace Search;
 
 namespace {
 
+constexpr int SEARCHEDLIST_CAPACITY = 32;
+using SearchedList                  = ValueList<Move, SEARCHEDLIST_CAPACITY>;
+
 // (*Scalers):
 // The values with Scaler asterisks have proven non-linear scaling.
 // They are optimized to time controls of 180 + 1.8 and longer,
@@ -119,16 +122,16 @@ void  update_pv(Move* pv, Move move, const Move* childPv);
 void  update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus);
 void  update_quiet_histories(
    const Position& pos, Stack* ss, Search::Worker& workerThread, Move move, int bonus);
-void update_all_stats(const Position&      pos,
-                      Stack*               ss,
-                      Search::Worker&      workerThread,
-                      Move                 bestMove,
-                      Square               prevSq,
-                      ValueList<Move, 32>& quietsSearched,
-                      ValueList<Move, 32>& capturesSearched,
-                      Depth                depth,
-                      Move                 TTMove,
-                      int                  moveCount);
+void update_all_stats(const Position& pos,
+                      Stack*          ss,
+                      Search::Worker& workerThread,
+                      Move            bestMove,
+                      Square          prevSq,
+                      SearchedList&   quietsSearched,
+                      SearchedList&   capturesSearched,
+                      Depth           depth,
+                      Move            TTMove,
+                      int             moveCount);
 
 }  // namespace
 
@@ -536,7 +539,6 @@ void Search::Worker::undo_null_move(Position& pos) { pos.undo_null_move(); }
 // Reset histories, usually before a new game
 void Search::Worker::clear() {
     mainHistory.fill(67);
-    lowPlyHistory.fill(107);
     captureHistory.fill(-688);
     pawnHistory.fill(-1287);
     pawnCorrectionHistory.fill(5);
@@ -606,8 +608,8 @@ Value Search::Worker::search(
     int   priorReduction;
     Piece movedPiece;
 
-    ValueList<Move, 32> capturesSearched;
-    ValueList<Move, 32> quietsSearched;
+    SearchedList capturesSearched;
+    SearchedList quietsSearched;
 
     // Step 1. Initialize node
     Worker* thisThread = this;
@@ -857,8 +859,8 @@ Value Search::Worker::search(
     {
         assert(eval - beta >= 0);
 
-        // Null move dynamic reduction based on depth and eval
-        Depth R = std::min(int(eval - beta) / 213, 6) + depth / 3 + 5;
+        // Null move dynamic reduction based on depth
+        Depth R = 7 + depth / 3;
 
         ss->currentMove                   = Move::null();
         ss->continuationHistory           = &thisThread->continuationHistory[0][0][NO_PIECE][0];
@@ -1083,7 +1085,7 @@ moves_loop:  // When in check, search starts here
 
                 lmrDepth += history / 3388;
 
-                Value baseFutility = (bestMove ? 46 : 138 + std::abs(history / 300));
+                Value baseFutility = (bestMove ? 46 : 230);
                 Value futilityValue =
                   ss->staticEval + baseFutility + 117 * lmrDepth + 102 * (ss->staticEval > alpha);
 
@@ -1207,8 +1209,7 @@ moves_loop:  // When in check, search starts here
         if ((ss + 1)->cutoffCnt > 2)
             r += 1036 + allNode * 848;
 
-        if (!capture && !givesCheck && ss->quietMoveStreak >= 2)
-            r += (ss->quietMoveStreak - 1) * 50;
+        r += (ss + 1)->quietMoveStreak * 50;
 
         // For first picked move (ttMove) reduce reduction
         if (move == ttData.move)
@@ -1392,7 +1393,7 @@ moves_loop:  // When in check, search starts here
 
         // If the move is worse than some previously searched move,
         // remember it, to update its stats later.
-        if (move != bestMove && moveCount <= 32)
+        if (move != bestMove && moveCount <= SEARCHEDLIST_CAPACITY)
         {
             if (capture)
                 capturesSearched.push_back(move);
@@ -1835,16 +1836,16 @@ void update_pv(Move* pv, Move move, const Move* childPv) {
 
 
 // Updates stats at the end of search() when a bestMove is found
-void update_all_stats(const Position&      pos,
-                      Stack*               ss,
-                      Search::Worker&      workerThread,
-                      Move                 bestMove,
-                      Square               prevSq,
-                      ValueList<Move, 32>& quietsSearched,
-                      ValueList<Move, 32>& capturesSearched,
-                      Depth                depth,
-                      Move                 ttMove,
-                      int                  moveCount) {
+void update_all_stats(const Position& pos,
+                      Stack*          ss,
+                      Search::Worker& workerThread,
+                      Move            bestMove,
+                      Square          prevSq,
+                      SearchedList&   quietsSearched,
+                      SearchedList&   capturesSearched,
+                      Depth           depth,
+                      Move            ttMove,
+                      int             moveCount) {
 
     CapturePieceToHistory& captureHistory = workerThread.captureHistory;
     Piece                  movedPiece     = pos.moved_piece(bestMove);

src/timeman.cpp

@@ -85,16 +85,13 @@ void TimeManagement::init(Search::LimitsType& limits,
     // with constants are involved.
     const int64_t   scaleFactor = useNodesTime ? npmsec : 1;
     const TimePoint scaledTime  = limits.time[us] / scaleFactor;
-    const TimePoint scaledInc   = limits.inc[us] / scaleFactor;
 
     // Maximum move horizon
     int centiMTG = limits.movestogo ? std::min(limits.movestogo * 100, 5000) : 5051;
 
     // If less than one second, gradually reduce mtg
-    if (scaledTime < 1000 && double(centiMTG) / scaledInc > 5.051)
-    {
+    if (scaledTime < 1000)
         centiMTG = scaledTime * 5.051;
-    }
 
     // Make sure timeLeft is > 0 since we may use it as a divisor
     TimePoint timeLeft =