+/*
+ 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);
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