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) 2015-2019 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"

#include "tt.h"

ThreadPool Threads; // Global object

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

/// in idle_loop(). Note that 'searching' and 'exit' should be alredy set.

Thread::Thread(size_t n) : idx(n), stdThread(&Thread::idle_loop, this) {

  wait_for_search_finished();

}

/// Thread destructor wakes up the thread in idle_loop() and waits

/// for its termination. Thread should be already waiting.

Thread::~Thread() {

  assert(!searching);

  exit = true;

  start_searching();

  stdThread.join();

}

/// Thread::clear() reset histories, usually before a new game

void Thread::clear() {

  counterMoves.fill(MOVE_NONE);

  mainHistory.fill(0);

  captureHistory.fill(0);

  for (auto& to : continuationHistory)

      for (auto& h : to)

          h->fill(0);

  continuationHistory[NO_PIECE][0]->fill(Search::CounterMovePruneThreshold - 1);

}

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

void Thread::start_searching() {

  std::lock_guard<Mutex> lk(mutex);

  searching = true;

  cv.notify_one(); // Wake up the thread in idle_loop()

}

/// Thread::wait_for_search_finished() blocks on the condition variable

/// until the thread has finished searching.

void Thread::wait_for_search_finished() {

  std::unique_lock<Mutex> lk(mutex);

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

}

/// Thread::idle_loop() is where the thread is parked, blocked on the

/// condition variable, when it has no work to do.

void Thread::idle_loop() {

  // If OS already scheduled us on a different group than 0 then don't overwrite

  // the choice, eventually we are one of many one-threaded processes running on

  // some Windows NUMA hardware, for instance in fishtest. To make it simple,

  // just check if running threads are below a threshold, in this case all this

  // NUMA machinery is not needed.

  if (Options["Threads"] > 8)

      WinProcGroup::bindThisThread(idx);

  while (true)

  {

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

      searching = false;

      cv.notify_one(); // Wake up anyone waiting for search finished

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

      if (exit)

          return;

      lk.unlock();

      search();

  }

}

/// ThreadPool::set() creates/destroys threads to match the requested number.

/// Created and launched threads will go immediately to sleep in idle_loop.

/// Upon resizing, threads are recreated to allow for binding if necessary.

void ThreadPool::set(size_t requested) {

  if (size() > 0) { // destroy any existing thread(s)

      main()->wait_for_search_finished();

      while (size() > 0)

          delete back(), pop_back();

  }

  if (requested > 0) { // create new thread(s)

      push_back(new MainThread(0));

      while (size() < requested)

          push_back(new Thread(size()));

      clear();

  }

  // Reallocate the hash with the new threadpool size

  TT.resize(Options["Hash"]);

}

/// ThreadPool::clear() sets threadPool data to initial values.

void ThreadPool::clear() {

  for (Thread* th : *this)

      th->clear();

  main()->callsCnt = 0;

  main()->previousScore = VALUE_INFINITE;

  main()->previousTimeReduction = 1.0;

}

/// ThreadPool::start_thinking() wakes up main thread waiting in idle_loop() and

/// returns immediately. Main thread will wake up other threads and start the search.

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

                                const Search::LimitsType& limits, bool ponderMode) {

  main()->wait_for_search_finished();

  stopOnPonderhit = stop = false;

  ponder = ponderMode;

  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.emplace_back(m);

  if (!rootMoves.empty())

      Tablebases::rank_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

  // We use Position::set() to set root position across threads. But there are

  // some StateInfo fields (previous, pliesFromNull, capturedPiece) that cannot

  // be deduced from a fen string, so set() clears them and to not lose the info

  // we need to backup and later restore setupStates->back(). Note that setupStates

  // is shared by threads but is accessed in read-only mode.

  StateInfo tmp = setupStates->back();

  for (Thread* th : *this)

  {

      th->nodes = th->tbHits = th->nmpMinPly = 0;

      th->rootDepth = th->completedDepth = DEPTH_ZERO;

      th->rootMoves = rootMoves;

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

  }

  setupStates->back() = tmp;

  main()->start_searching();

}