Move pawn and material tables under Thread class

This change allows to remove some quite a bit of code
and seems the natural thing to do.

Introduced file thread.cpp to move away from search.cpp a lot
of threads related stuff.

No functional change.

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

src/thread.cpp

@@ -0,0 +1,333 @@
+/*
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+
+  Stockfish is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  Stockfish is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <iostream>
+
+#include "thread.h"
+#include "ucioption.h"
+
+ThreadsManager ThreadsMgr; // Global object definition
+
+namespace {
+
+ // init_thread() is the function which is called when a new thread is
+ // launched. It simply calls the idle_loop() function with the supplied
+ // threadID. There are two versions of this function; one for POSIX
+ // threads and one for Windows threads.
+
+#if !defined(_MSC_VER)
+
+  void* init_thread(void* threadID) {
+
+    ThreadsMgr.idle_loop(*(int*)threadID, NULL);
+    return NULL;
+  }
+
+#else
+
+  DWORD WINAPI init_thread(LPVOID threadID) {
+
+    ThreadsMgr.idle_loop(*(int*)threadID, NULL);
+    return 0;
+  }
+
+#endif
+
+}
+
+
+// read_uci_options() updates number of active threads and other internal
+// parameters according to the UCI options values. It is called before
+// to start a new search.
+
+void ThreadsManager::read_uci_options() {
+
+  maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
+  minimumSplitDepth       = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
+  useSleepingThreads      = Options["Use Sleeping Threads"].value<bool>();
+  activeThreads           = Options["Threads"].value<int>();
+}
+
+// init_threads() is called during startup. Initializes locks and condition
+// variables and launches all threads sending them immediately to sleep.
+
+void ThreadsManager::init_threads() {
+
+  int i, arg[MAX_THREADS];
+  bool ok;
+
+  // This flag is needed to properly end the threads when program exits
+  allThreadsShouldExit = false;
+
+  // Threads will sent to sleep as soon as created, only main thread is kept alive
+  activeThreads = 1;
+
+  lock_init(&mpLock);
+
+  for (i = 0; i < MAX_THREADS; i++)
+  {
+      // Initialize thread and split point locks
+      lock_init(&threads[i].sleepLock);
+      cond_init(&threads[i].sleepCond);
+
+      for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
+          lock_init(&(threads[i].splitPoints[j].lock));
+
+      // All threads but first should be set to THREAD_INITIALIZING
+      threads[i].state = (i == 0 ? THREAD_SEARCHING : THREAD_INITIALIZING);
+
+      // Not in Threads c'tor to avoid global initialization order issues
+      threads[i].pawnTable.init();
+      threads[i].materialTable.init();
+  }
+
+  // Create and startup the threads
+  for (i = 1; i < MAX_THREADS; i++)
+  {
+      arg[i] = i;
+
+#if !defined(_MSC_VER)
+      pthread_t pthread[1];
+      ok = (pthread_create(pthread, NULL, init_thread, (void*)(&arg[i])) == 0);
+      pthread_detach(pthread[0]);
+#else
+      ok = (CreateThread(NULL, 0, init_thread, (LPVOID)(&arg[i]), 0, NULL) != NULL);
+#endif
+      if (!ok)
+      {
+          std::cout << "Failed to create thread number " << i << std::endl;
+          exit(EXIT_FAILURE);
+      }
+
+      // Wait until the thread has finished launching and is gone to sleep
+      while (threads[i].state == THREAD_INITIALIZING) {}
+  }
+}
+
+
+// exit_threads() is called when the program exits. It makes all the
+// helper threads exit cleanly.
+
+void ThreadsManager::exit_threads() {
+
+  // Force the woken up threads to exit idle_loop() and hence terminate
+  allThreadsShouldExit = true;
+
+  for (int i = 0; i < MAX_THREADS; i++)
+  {
+      // Wake up all the threads and waits for termination
+      if (i != 0)
+      {
+          threads[i].wake_up();
+          while (threads[i].state != THREAD_TERMINATED) {}
+      }
+
+      // Now we can safely destroy the locks and wait conditions
+      lock_destroy(&threads[i].sleepLock);
+      cond_destroy(&threads[i].sleepCond);
+
+      for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
+          lock_destroy(&(threads[i].splitPoints[j].lock));
+  }
+
+  lock_destroy(&mpLock);
+}
+
+
+// cutoff_at_splitpoint() checks whether a beta cutoff has occurred in
+// the thread's currently active split point, or in some ancestor of
+// the current split point.
+
+bool ThreadsManager::cutoff_at_splitpoint(int threadID) const {
+
+  assert(threadID >= 0 && threadID < activeThreads);
+
+  SplitPoint* sp = threads[threadID].splitPoint;
+
+  for ( ; sp && !sp->betaCutoff; sp = sp->parent) {}
+  return sp != NULL;
+}
+
+
+// thread_is_available() checks whether the thread with threadID "slave" is
+// available to help the thread with threadID "master" at a split point. An
+// obvious requirement is that "slave" must be idle. With more than two
+// threads, this is not by itself sufficient:  If "slave" is the master of
+// some active split point, it is only available as a slave to the other
+// threads which are busy searching the split point at the top of "slave"'s
+// split point stack (the "helpful master concept" in YBWC terminology).
+
+bool ThreadsManager::thread_is_available(int slave, int master) const {
+
+  assert(slave >= 0 && slave < activeThreads);
+  assert(master >= 0 && master < activeThreads);
+  assert(activeThreads > 1);
+
+  if (threads[slave].state != THREAD_AVAILABLE || slave == master)
+      return false;
+
+  // Make a local copy to be sure doesn't change under our feet
+  int localActiveSplitPoints = threads[slave].activeSplitPoints;
+
+  // No active split points means that the thread is available as
+  // a slave for any other thread.
+  if (localActiveSplitPoints == 0 || activeThreads == 2)
+      return true;
+
+  // Apply the "helpful master" concept if possible. Use localActiveSplitPoints
+  // that is known to be > 0, instead of threads[slave].activeSplitPoints that
+  // could have been set to 0 by another thread leading to an out of bound access.
+  if (threads[slave].splitPoints[localActiveSplitPoints - 1].slaves[master])
+      return true;
+
+  return false;
+}
+
+
+// available_thread_exists() tries to find an idle thread which is available as
+// a slave for the thread with threadID "master".
+
+bool ThreadsManager::available_thread_exists(int master) const {
+
+  assert(master >= 0 && master < activeThreads);
+  assert(activeThreads > 1);
+
+  for (int i = 0; i < activeThreads; i++)
+      if (thread_is_available(i, master))
+          return true;
+
+  return false;
+}
+
+
+// split() does the actual work of distributing the work at a node between
+// several available threads. If it does not succeed in splitting the
+// node (because no idle threads are available, or because we have no unused
+// split point objects), the function immediately returns. If splitting is
+// possible, a SplitPoint object is initialized with all the data that must be
+// copied to the helper threads and we tell our helper threads that they have
+// been assigned work. This will cause them to instantly leave their idle loops and
+// call search().When all threads have returned from search() then split() returns.
+
+template <bool Fake>
+void ThreadsManager::split(Position& pos, SearchStack* ss, Value* alpha, const Value beta,
+                           Value* bestValue, Depth depth, Move threatMove,
+                           int moveCount, MovePicker* mp, bool pvNode) {
+  assert(pos.is_ok());
+  assert(*bestValue >= -VALUE_INFINITE);
+  assert(*bestValue <= *alpha);
+  assert(*alpha < beta);
+  assert(beta <= VALUE_INFINITE);
+  assert(depth > DEPTH_ZERO);
+  assert(pos.thread() >= 0 && pos.thread() < activeThreads);
+  assert(activeThreads > 1);
+
+  int i, master = pos.thread();
+  Thread& masterThread = threads[master];
+
+  lock_grab(&mpLock);
+
+  // If no other thread is available to help us, or if we have too many
+  // active split points, don't split.
+  if (   !available_thread_exists(master)
+      || masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
+  {
+      lock_release(&mpLock);
+      return;
+  }
+
+  // Pick the next available split point object from the split point stack
+  SplitPoint& splitPoint = masterThread.splitPoints[masterThread.activeSplitPoints++];
+
+  // Initialize the split point object
+  splitPoint.parent = masterThread.splitPoint;
+  splitPoint.master = master;
+  splitPoint.betaCutoff = false;
+  splitPoint.depth = depth;
+  splitPoint.threatMove = threatMove;
+  splitPoint.alpha = *alpha;
+  splitPoint.beta = beta;
+  splitPoint.pvNode = pvNode;
+  splitPoint.bestValue = *bestValue;
+  splitPoint.mp = mp;
+  splitPoint.moveCount = moveCount;
+  splitPoint.pos = &pos;
+  splitPoint.nodes = 0;
+  splitPoint.ss = ss;
+  for (i = 0; i < activeThreads; i++)
+      splitPoint.slaves[i] = 0;
+
+  masterThread.splitPoint = &splitPoint;
+
+  // If we are here it means we are not available
+  assert(masterThread.state != THREAD_AVAILABLE);
+
+  int workersCnt = 1; // At least the master is included
+
+  // Allocate available threads setting state to THREAD_BOOKED
+  for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
+      if (thread_is_available(i, master))
+      {
+          threads[i].state = THREAD_BOOKED;
+          threads[i].splitPoint = &splitPoint;
+          splitPoint.slaves[i] = 1;
+          workersCnt++;
+      }
+
+  assert(Fake || workersCnt > 1);
+
+  // We can release the lock because slave threads are already booked and master is not available
+  lock_release(&mpLock);
+
+  // Tell the threads that they have work to do. This will make them leave
+  // their idle loop.
+  for (i = 0; i < activeThreads; i++)
+      if (i == master || splitPoint.slaves[i])
+      {
+          assert(i == master || threads[i].state == THREAD_BOOKED);
+
+          threads[i].state = THREAD_WORKISWAITING; // This makes the slave to exit from idle_loop()
+
+          if (useSleepingThreads && i != master)
+              threads[i].wake_up();
+      }
+
+  // Everything is set up. The master thread enters the idle loop, from
+  // which it will instantly launch a search, because its state is
+  // THREAD_WORKISWAITING.  We send the split point as a second parameter to the
+  // idle loop, which means that the main thread will return from the idle
+  // loop when all threads have finished their work at this split point.
+  idle_loop(master, &splitPoint);
+
+  // We have returned from the idle loop, which means that all threads are
+  // finished. Update alpha and bestValue, and return.
+  lock_grab(&mpLock);
+
+  *alpha = splitPoint.alpha;
+  *bestValue = splitPoint.bestValue;
+  masterThread.activeSplitPoints--;
+  masterThread.splitPoint = splitPoint.parent;
+  pos.set_nodes_searched(pos.nodes_searched() + splitPoint.nodes);
+
+  lock_release(&mpLock);
+}
+
+// Explicit template instantiations
+template void ThreadsManager::split<0>(Position&, SearchStack*, Value*, const Value, Value*, Depth, Move, int, MovePicker*, bool);
+template void ThreadsManager::split<1>(Position&, SearchStack*, Value*, const Value, Value*, Depth, Move, int, MovePicker*, bool);