mirror of
https://github.com/sockspls/badfish
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345 lines
11 KiB
C++
345 lines
11 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <iostream>
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#include "thread.h"
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#include "ucioption.h"
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ThreadsManager Threads; // Global object definition
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namespace { extern "C" {
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// start_routine() is the C function which is called when a new thread
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// is launched. It simply calls idle_loop() with the supplied threadID.
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// There are two versions of this function; one for POSIX threads and
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// one for Windows threads.
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#if defined(_MSC_VER)
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DWORD WINAPI start_routine(LPVOID threadID) {
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Threads.idle_loop(*(int*)threadID, NULL);
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return 0;
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}
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#else
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void* start_routine(void* threadID) {
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Threads.idle_loop(*(int*)threadID, NULL);
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return NULL;
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}
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#endif
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} }
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// wake_up() wakes up the thread, normally at the beginning of the search or,
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// if "sleeping threads" is used, when there is some work to do.
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void Thread::wake_up() {
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lock_grab(&sleepLock);
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cond_signal(&sleepCond);
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lock_release(&sleepLock);
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}
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// cutoff_occurred() checks whether a beta cutoff has occurred in
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// the thread's currently active split point, or in some ancestor of
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// the current split point.
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bool Thread::cutoff_occurred() const {
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for (SplitPoint* sp = splitPoint; sp; sp = sp->parent)
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if (sp->is_betaCutoff)
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return true;
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return false;
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}
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// is_available_to() checks whether the thread is available to help the thread with
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// threadID "master" at a split point. An obvious requirement is that thread must be
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// idle. With more than two threads, this is not by itself sufficient: If the thread
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// is the master of some active split point, it is only available as a slave to the
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// threads which are busy searching the split point at the top of "slave"'s split
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// point stack (the "helpful master concept" in YBWC terminology).
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bool Thread::is_available_to(int master) const {
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if (state != AVAILABLE)
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return false;
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// Make a local copy to be sure doesn't become zero under our feet while
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// testing next condition and so leading to an out of bound access.
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int localActiveSplitPoints = activeSplitPoints;
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// No active split points means that the thread is available as a slave for any
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// other thread otherwise apply the "helpful master" concept if possible.
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if ( !localActiveSplitPoints
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|| splitPoints[localActiveSplitPoints - 1].is_slave[master])
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return true;
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return false;
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}
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// read_uci_options() updates number of active threads and other internal
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// parameters according to the UCI options values. It is called before
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// to start a new search.
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void ThreadsManager::read_uci_options() {
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maxThreadsPerSplitPoint = Options["Maximum Number of Threads per Split Point"].value<int>();
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minimumSplitDepth = Options["Minimum Split Depth"].value<int>() * ONE_PLY;
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useSleepingThreads = Options["Use Sleeping Threads"].value<bool>();
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activeThreads = Options["Threads"].value<int>();
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}
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// init() is called during startup. Initializes locks and condition variables
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// and launches all threads sending them immediately to sleep.
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void ThreadsManager::init() {
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int threadID[MAX_THREADS];
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// This flag is needed to properly end the threads when program exits
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allThreadsShouldExit = false;
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// Threads will sent to sleep as soon as created, only main thread is kept alive
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activeThreads = 1;
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threads[0].state = Thread::SEARCHING;
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// Allocate pawn and material hash tables for main thread
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init_hash_tables();
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// Initialize threads lock, used when allocating slaves during splitting
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lock_init(&threadsLock);
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// Initialize sleep and split point locks
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for (int i = 0; i < MAX_THREADS; i++)
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{
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lock_init(&threads[i].sleepLock);
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cond_init(&threads[i].sleepCond);
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for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
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lock_init(&(threads[i].splitPoints[j].lock));
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}
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// Create and startup all the threads but the main that is already running
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for (int i = 1; i < MAX_THREADS; i++)
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{
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threads[i].state = Thread::INITIALIZING;
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threadID[i] = i;
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#if defined(_MSC_VER)
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bool ok = (CreateThread(NULL, 0, start_routine, (LPVOID)&threadID[i], 0, NULL) != NULL);
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#else
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pthread_t pthreadID;
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bool ok = (pthread_create(&pthreadID, NULL, start_routine, (void*)&threadID[i]) == 0);
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pthread_detach(pthreadID);
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#endif
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if (!ok)
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{
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std::cout << "Failed to create thread number " << i << std::endl;
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::exit(EXIT_FAILURE);
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}
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// Wait until the thread has finished launching and is gone to sleep
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while (threads[i].state == Thread::INITIALIZING) {}
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}
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}
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// exit() is called to cleanly terminate the threads when the program finishes
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void ThreadsManager::exit() {
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// Force the woken up threads to exit idle_loop() and hence terminate
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allThreadsShouldExit = true;
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for (int i = 0; i < MAX_THREADS; i++)
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{
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// Wake up all the threads and wait for termination
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if (i != 0)
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{
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threads[i].wake_up();
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while (threads[i].state != Thread::TERMINATED) {}
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}
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// Now we can safely destroy locks and wait conditions
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lock_destroy(&threads[i].sleepLock);
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cond_destroy(&threads[i].sleepCond);
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for (int j = 0; j < MAX_ACTIVE_SPLIT_POINTS; j++)
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lock_destroy(&(threads[i].splitPoints[j].lock));
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}
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lock_destroy(&threadsLock);
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}
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// init_hash_tables() dynamically allocates pawn and material hash tables
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// according to the number of active threads. This avoids preallocating
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// memory for all possible threads if only few are used as, for instance,
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// on mobile devices where memory is scarce and allocating for MAX_THREADS
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// threads could even result in a crash.
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void ThreadsManager::init_hash_tables() {
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for (int i = 0; i < activeThreads; i++)
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{
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threads[i].pawnTable.init();
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threads[i].materialTable.init();
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}
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}
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// available_slave_exists() tries to find an idle thread which is available as
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// a slave for the thread with threadID "master".
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bool ThreadsManager::available_slave_exists(int master) const {
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assert(master >= 0 && master < activeThreads);
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for (int i = 0; i < activeThreads; i++)
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if (i != master && threads[i].is_available_to(master))
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return true;
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return false;
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}
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// split() does the actual work of distributing the work at a node between
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// several available threads. If it does not succeed in splitting the
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// node (because no idle threads are available, or because we have no unused
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// split point objects), the function immediately returns. If splitting is
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// possible, a SplitPoint object is initialized with all the data that must be
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// copied to the helper threads and we tell our helper threads that they have
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// been assigned work. This will cause them to instantly leave their idle loops and
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// call search().When all threads have returned from search() then split() returns.
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template <bool Fake>
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Value ThreadsManager::split(Position& pos, SearchStack* ss, Value alpha, Value beta,
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Value bestValue, Depth depth, Move threatMove,
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int moveCount, MovePicker* mp, int nodeType) {
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assert(pos.is_ok());
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assert(bestValue >= -VALUE_INFINITE);
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assert(bestValue <= alpha);
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assert(alpha < beta);
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assert(beta <= VALUE_INFINITE);
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assert(depth > DEPTH_ZERO);
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assert(pos.thread() >= 0 && pos.thread() < activeThreads);
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assert(activeThreads > 1);
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int i, master = pos.thread();
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Thread& masterThread = threads[master];
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// If we already have too many active split points, don't split
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if (masterThread.activeSplitPoints >= MAX_ACTIVE_SPLIT_POINTS)
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return bestValue;
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// Pick the next available split point object from the split point stack
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SplitPoint* sp = masterThread.splitPoints + masterThread.activeSplitPoints;
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// Initialize the split point object
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sp->parent = masterThread.splitPoint;
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sp->master = master;
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sp->is_betaCutoff = false;
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sp->depth = depth;
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sp->threatMove = threatMove;
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sp->alpha = alpha;
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sp->beta = beta;
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sp->nodeType = nodeType;
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sp->bestValue = bestValue;
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sp->mp = mp;
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sp->moveCount = moveCount;
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sp->pos = &pos;
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sp->nodes = 0;
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sp->ss = ss;
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for (i = 0; i < activeThreads; i++)
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sp->is_slave[i] = false;
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// If we are here it means we are not available
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assert(masterThread.state == Thread::SEARCHING);
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int workersCnt = 1; // At least the master is included
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// Try to allocate available threads and ask them to start searching setting
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// the state to Thread::WORKISWAITING, this must be done under lock protection
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// to avoid concurrent allocation of the same slave by another master.
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lock_grab(&threadsLock);
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for (i = 0; !Fake && i < activeThreads && workersCnt < maxThreadsPerSplitPoint; i++)
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if (i != master && threads[i].is_available_to(master))
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{
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workersCnt++;
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sp->is_slave[i] = true;
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threads[i].splitPoint = sp;
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// This makes the slave to exit from idle_loop()
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threads[i].state = Thread::WORKISWAITING;
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if (useSleepingThreads)
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threads[i].wake_up();
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}
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lock_release(&threadsLock);
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// We failed to allocate even one slave, return
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if (!Fake && workersCnt == 1)
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return bestValue;
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masterThread.splitPoint = sp;
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masterThread.activeSplitPoints++;
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masterThread.state = Thread::WORKISWAITING;
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// Everything is set up. The master thread enters the idle loop, from
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// which it will instantly launch a search, because its state is
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// Thread::WORKISWAITING. We send the split point as a second parameter to
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// the idle loop, which means that the main thread will return from the idle
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// loop when all threads have finished their work at this split point.
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idle_loop(master, sp);
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// In helpful master concept a master can help only a sub-tree, and
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// because here is all finished is not possible master is booked.
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assert(masterThread.state == Thread::AVAILABLE);
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// We have returned from the idle loop, which means that all threads are
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// finished. Note that changing state and decreasing activeSplitPoints is done
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// under lock protection to avoid a race with Thread::is_available_to().
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lock_grab(&threadsLock);
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masterThread.state = Thread::SEARCHING;
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masterThread.activeSplitPoints--;
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lock_release(&threadsLock);
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masterThread.splitPoint = sp->parent;
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pos.set_nodes_searched(pos.nodes_searched() + sp->nodes);
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return sp->bestValue;
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}
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// Explicit template instantiations
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template Value ThreadsManager::split<false>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
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template Value ThreadsManager::split<true>(Position&, SearchStack*, Value, Value, Value, Depth, Move, int, MovePicker*, int);
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