Subversion Repositories Games.Chess Giants

/*

  Stockfish, a UCI chess playing engine derived from Glaurung 2.1

  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)

  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad

  Copyright (C) 2015-2016 Marco Costalba, Joona Kiiski, Gary Linscott, 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 <algorithm> // For std::count

#include <cassert>

#include "movegen.h"

#include "search.h"

#include "thread.h"

#include "uci.h"

#include "syzygy/tbprobe.h"

ThreadPool Threads; // Global object

/// Thread constructor launches the thread and then waits until it goes to sleep

/// in idle_loop().

Thread::Thread() {

  resetCalls = exit = false;

  maxPly = callsCnt = 0;

  tbHits = 0;

  history.clear();

  counterMoves.clear();

  idx = Threads.size(); // Start from 0

  std::unique_lock<Mutex> lk(mutex);

  searching = true;

  nativeThread = std::thread(&Thread::idle_loop, this);

  sleepCondition.wait(lk, [&]{ return !searching; });

}

/// Thread destructor waits for thread termination before returning

Thread::~Thread() {

  mutex.lock();

  exit = true;

  sleepCondition.notify_one();

  mutex.unlock();

  nativeThread.join();

}

/// Thread::wait_for_search_finished() waits on sleep condition

/// until not searching

void Thread::wait_for_search_finished() {

  std::unique_lock<Mutex> lk(mutex);

  sleepCondition.wait(lk, [&]{ return !searching; });

}

/// Thread::wait() waits on sleep condition until condition is true

void Thread::wait(std::atomic_bool& condition) {

  std::unique_lock<Mutex> lk(mutex);

  sleepCondition.wait(lk, [&]{ return bool(condition); });

}

/// Thread::start_searching() wakes up the thread that will start the search

void Thread::start_searching(bool resume) {

  std::unique_lock<Mutex> lk(mutex);

  if (!resume)

      searching = true;

  sleepCondition.notify_one();

}

/// Thread::idle_loop() is where the thread is parked when it has no work to do

void Thread::idle_loop() {

  while (!exit)

  {

      std::unique_lock<Mutex> lk(mutex);

      searching = false;

      while (!searching && !exit)

      {

          sleepCondition.notify_one(); // Wake up any waiting thread

          sleepCondition.wait(lk);

      }

      lk.unlock();

      if (!exit)

          search();

  }

}

/// ThreadPool::init() creates and launches requested threads that will go

/// immediately to sleep. We cannot use a constructor because Threads is a

/// static object and we need a fully initialized engine at this point due to

/// allocation of Endgames in the Thread constructor.

void ThreadPool::init() {

  push_back(new MainThread);

  read_uci_options();

}

/// ThreadPool::exit() terminates threads before the program exits. Cannot be

/// done in destructor because threads must be terminated before deleting any

/// static objects while still in main().

void ThreadPool::exit() {

  while (size())

      delete back(), pop_back();

}

/// ThreadPool::read_uci_options() updates internal threads parameters from the

/// corresponding UCI options and creates/destroys threads to match requested

/// number. Thread objects are dynamically allocated.

void ThreadPool::read_uci_options() {

  size_t requested = Options["Threads"];

  assert(requested > 0);

  while (size() < requested)

      push_back(new Thread);

  while (size() > requested)

      delete back(), pop_back();

}

/// ThreadPool::nodes_searched() returns the number of nodes searched

uint64_t ThreadPool::nodes_searched() const {

  uint64_t nodes = 0;

  for (Thread* th : *this)

      nodes += th->rootPos.nodes_searched();

  return nodes;

}

/// ThreadPool::tb_hits() returns the number of TB hits

uint64_t ThreadPool::tb_hits() const {

  uint64_t hits = 0;

  for (Thread* th : *this)

      hits += th->tbHits;

  return hits;

}

/// ThreadPool::start_thinking() wakes up the main thread sleeping in idle_loop()

/// and starts a new search, then returns immediately.

void ThreadPool::start_thinking(Position& pos, StateListPtr& states,

                                const Search::LimitsType& limits) {

  main()->wait_for_search_finished();

  Search::Signals.stopOnPonderhit = Search::Signals.stop = false;

  Search::Limits = limits;

  Search::RootMoves rootMoves;

  for (const auto& m : MoveList<LEGAL>(pos))

      if (   limits.searchmoves.empty()

          || std::count(limits.searchmoves.begin(), limits.searchmoves.end(), m))

          rootMoves.push_back(Search::RootMove(m));

  if (!rootMoves.empty())

      Tablebases::filter_root_moves(pos, rootMoves);

  // After ownership transfer 'states' becomes empty, so if we stop the search

  // and call 'go' again without setting a new position states.get() == NULL.

  assert(states.get() || setupStates.get());

  if (states.get())

      setupStates = std::move(states); // Ownership transfer, states is now empty

  StateInfo tmp = setupStates->back();

  for (Thread* th : Threads)

  {

      th->maxPly = 0;

      th->tbHits = 0;

      th->rootDepth = DEPTH_ZERO;

      th->rootMoves = rootMoves;

      th->rootPos.set(pos.fen(), pos.is_chess960(), &setupStates->back(), th);

  }

  setupStates->back() = tmp; // Restore st->previous, cleared by Position::set()

  main()->start_searching();

}