string uci_pv(const Position& pos, Depth depth, Value alpha, Value beta);
struct Skill {
- Skill(int l, size_t rootSize) : level(l),
- candidates(l < 20 ? std::min(4, (int)rootSize) : 0),
- best(MOVE_NONE) {}
- ~Skill() {
- if (candidates) // Swap best PV line with the sub-optimal one
- std::swap(RootMoves[0], *std::find(RootMoves.begin(),
- RootMoves.end(), best ? best : pick_move()));
- }
-
- size_t candidates_size() const { return candidates; }
+ Skill(int l) : level(l) {}
+ bool enabled() const { return level < 20; }
bool time_to_pick(Depth depth) const { return depth / ONE_PLY == 1 + level; }
- Move pick_move();
+ Move best_move(size_t multiPV) { return best ? best : pick_best(multiPV); }
+ Move pick_best(size_t multiPV);
int level;
- size_t candidates;
- Move best;
+ Move best = MOVE_NONE;
};
} // namespace
CheckInfo ci(pos);
const bool leaf = (depth == 2 * ONE_PLY);
- for (MoveList<LEGAL> it(pos); *it; ++it)
+ for (const ExtMove& ms : MoveList<LEGAL>(pos))
{
if (Root && depth <= ONE_PLY)
cnt = 1, nodes++;
else
{
- pos.do_move(*it, st, ci, pos.gives_check(*it, ci));
+ pos.do_move(ms.move, st, ci, pos.gives_check(ms.move, ci));
cnt = leaf ? MoveList<LEGAL>(pos).size() : perft<false>(pos, depth - ONE_PLY);
nodes += cnt;
- pos.undo_move(*it);
+ pos.undo_move(ms.move);
}
if (Root)
- sync_cout << UCI::move(*it, pos.is_chess960()) << ": " << cnt << sync_endl;
+ sync_cout << UCI::move(ms.move, pos.is_chess960()) << ": " << cnt << sync_endl;
}
return nodes;
}
}
}
- for (size_t i = 0; i < Threads.size(); ++i)
- Threads[i]->maxPly = 0;
+ for (Thread* th : Threads)
+ th->maxPly = 0;
Threads.timer->run = true;
Threads.timer->notify_one(); // Wake up the recurring timer
sync_cout << "bestmove " << UCI::move(RootMoves[0].pv[0], RootPos.is_chess960());
- if (RootMoves[0].pv.size() > 1)
+ if (RootMoves[0].pv.size() > 1 || RootMoves[0].extract_ponder_from_tt(RootPos))
std::cout << " ponder " << UCI::move(RootMoves[0].pv[1], RootPos.is_chess960());
std::cout << sync_endl;
Followupmoves.clear();
size_t multiPV = Options["MultiPV"];
- Skill skill(Options["Skill Level"], RootMoves.size());
+ Skill skill(Options["Skill Level"]);
+
+ // When playing with strength handicap enable MultiPV search that we will
+ // use behind the scenes to retrieve a set of possible moves.
+ if (skill.enabled())
+ multiPV = std::max(multiPV, (size_t)4);
- // Do we have to play with skill handicap? In this case enable MultiPV search
- // that we will use behind the scenes to retrieve a set of possible moves.
- multiPV = std::max(multiPV, skill.candidates_size());
+ multiPV = std::min(multiPV, RootMoves.size());
// Iterative deepening loop until requested to stop or target depth reached
while (++depth < DEPTH_MAX && !Signals.stop && (!Limits.depth || depth <= Limits.depth))
// Save the last iteration's scores before first PV line is searched and
// all the move scores except the (new) PV are set to -VALUE_INFINITE.
- for (size_t i = 0; i < RootMoves.size(); ++i)
- RootMoves[i].previousScore = RootMoves[i].score;
+ for (RootMove& rm : RootMoves)
+ rm.previousScore = rm.score;
// MultiPV loop. We perform a full root search for each PV line
- for (PVIdx = 0; PVIdx < std::min(multiPV, RootMoves.size()) && !Signals.stop; ++PVIdx)
+ for (PVIdx = 0; PVIdx < multiPV && !Signals.stop; ++PVIdx)
{
// Reset aspiration window starting size
if (depth >= 5 * ONE_PLY)
// When failing high/low give some update (without cluttering
// the UI) before a re-search.
- if ( (bestValue <= alpha || bestValue >= beta)
+ if ( multiPV == 1
+ && (bestValue <= alpha || bestValue >= beta)
&& Time::now() - SearchTime > 3000)
sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
sync_cout << "info nodes " << RootPos.nodes_searched()
<< " time " << Time::now() - SearchTime << sync_endl;
- else if ( PVIdx + 1 == std::min(multiPV, RootMoves.size())
- || Time::now() - SearchTime > 3000)
+ else if (PVIdx + 1 == multiPV || Time::now() - SearchTime > 3000)
sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
- // If skill levels are enabled and time is up, pick a sub-optimal best move
- if (skill.candidates_size() && skill.time_to_pick(depth))
- skill.pick_move();
+ // If skill level is enabled and time is up, pick a sub-optimal best move
+ if (skill.enabled() && skill.time_to_pick(depth))
+ skill.pick_best(multiPV);
// Have we found a "mate in x"?
if ( Limits.mate
}
}
}
+
+ // If skill level is enabled, swap best PV line with the sub-optimal one
+ if (skill.enabled())
+ std::swap(RootMoves[0], *std::find(RootMoves.begin(),
+ RootMoves.end(), skill.best_move(multiPV)));
}
splitPoint = ss->splitPoint;
bestMove = splitPoint->bestMove;
bestValue = splitPoint->bestValue;
- tte = NULL;
+ tte = nullptr;
ttHit = false;
ttMove = excludedMove = MOVE_NONE;
ttValue = VALUE_NONE;
// If ttMove is quiet, update killers, history, counter move and followup move on TT hit
if (ttValue >= beta && ttMove && !pos.capture_or_promotion(ttMove) && !inCheck)
- update_stats(pos, ss, ttMove, depth, NULL, 0);
+ update_stats(pos, ss, ttMove, depth, nullptr, 0);
return ttValue;
}
}
if (PvNode)
- (ss+1)->pv = NULL;
+ (ss+1)->pv = nullptr;
extension = DEPTH_ZERO;
captureOrPromotion = pos.capture_or_promotion(move);
newDepth = depth - ONE_PLY + extension;
// Step 13. Pruning at shallow depth
- if ( !captureOrPromotion
+ if ( !RootNode
+ && !captureOrPromotion
&& !inCheck
&& !dangerous
&& bestValue > VALUE_MATED_IN_MAX_PLY)
}
- // When playing with a strength handicap, choose best move among the first 'candidates'
- // RootMoves using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
+ // When playing with strength handicap, choose best move among a set of RootMoves
+ // using a statistical rule dependent on 'level'. Idea by Heinz van Saanen.
- Move Skill::pick_move() {
+ Move Skill::pick_best(size_t multiPV) {
// PRNG sequence should be non-deterministic, so we seed it with the time at init
static PRNG rng(Time::now());
// RootMoves are already sorted by score in descending order
- int variance = std::min(RootMoves[0].score - RootMoves[candidates - 1].score, PawnValueMg);
+ int variance = std::min(RootMoves[0].score - RootMoves[multiPV - 1].score, PawnValueMg);
int weakness = 120 - 2 * level;
int maxScore = -VALUE_INFINITE;
- best = MOVE_NONE;
// Choose best move. For each move score we add two terms both dependent on
- // weakness. One deterministic and bigger for weaker moves, and one random,
+ // weakness. One deterministic and bigger for weaker levels, and one random,
// then we choose the move with the resulting highest score.
- for (size_t i = 0; i < candidates; ++i)
+ for (size_t i = 0; i < multiPV; ++i)
{
int score = RootMoves[i].score;
- // Don't allow crazy blunders even at very low skills
- if (i > 0 && RootMoves[i - 1].score > score + 2 * PawnValueMg)
- break;
-
// This is our magic formula
score += ( weakness * int(RootMoves[0].score - score)
+ variance * (rng.rand<unsigned>() % weakness)) / 128;
size_t uciPVSize = std::min((size_t)Options["MultiPV"], RootMoves.size());
int selDepth = 0;
- for (size_t i = 0; i < Threads.size(); ++i)
- if (Threads[i]->maxPly > selDepth)
- selDepth = Threads[i]->maxPly;
+ for (Thread* th : Threads)
+ if (th->maxPly > selDepth)
+ selDepth = th->maxPly;
for (size_t i = 0; i < uciPVSize; ++i)
{
}
+ /// RootMove::extract_ponder_from_tt() is called in case we have no ponder move before
+ /// exiting the search, for instance in case we stop the search during a fail high at
+ /// root. We try hard to have a ponder move to return to the GUI, otherwise in case of
+ /// 'ponder on' we have nothing to think on.
+
+ Move RootMove::extract_ponder_from_tt(Position& pos)
+ {
+ StateInfo st;
+ bool found;
+
+ assert(pv.size() == 1);
+
+ pos.do_move(pv[0], st);
+ TTEntry* tte = TT.probe(pos.key(), found);
+ Move m = found ? tte->move() : MOVE_NONE;
+ if (!MoveList<LEGAL>(pos).contains(m))
+ m = MOVE_NONE;
+
+ pos.undo_move(pv[0]);
+ pv.push_back(m);
+ return m;
+ }
+
+
/// Thread::idle_loop() is where the thread is parked when it has no work to do
void Thread::idle_loop() {
// Pointer 'this_sp' is not null only if we are called from split(), and not
// at the thread creation. This means we are the split point's master.
- SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : NULL;
+ SplitPoint* this_sp = splitPointsSize ? activeSplitPoint : nullptr;
assert(!this_sp || (this_sp->masterThread == this && searching));
sp->mutex.lock();
- assert(activePosition == NULL);
+ assert(activePosition == nullptr);
activePosition = &pos;
assert(searching);
searching = false;
- activePosition = NULL;
+ activePosition = nullptr;
sp->slavesMask.reset(idx);
sp->allSlavesSearching = false;
sp->nodes += pos.nodes_searched();
for (size_t i = 0; i < Threads.size(); ++i)
{
const int size = Threads[i]->splitPointsSize; // Local copy
- sp = size ? &Threads[i]->splitPoints[size - 1] : NULL;
+ sp = size ? &Threads[i]->splitPoints[size - 1] : nullptr;
if ( sp
&& sp->allSlavesSearching
}
// Grab the lock to avoid races with Thread::notify_one()
- mutex.lock();
+ std::unique_lock<std::mutex> lk(mutex);
// If we are master and all slaves have finished then exit idle_loop
if (this_sp && this_sp->slavesMask.none())
{
assert(!searching);
- mutex.unlock();
break;
}
// If we are not searching, wait for a condition to be signaled instead of
// wasting CPU time polling for work.
if (!searching && !exit)
- sleepCondition.wait(mutex);
-
- mutex.unlock();
+ sleepCondition.wait(lk);
}
}
// Loop across all split points and sum accumulated SplitPoint nodes plus
// all the currently active positions nodes.
- for (size_t i = 0; i < Threads.size(); ++i)
- for (int j = 0; j < Threads[i]->splitPointsSize; ++j)
+ for (Thread* th : Threads)
+ for (int i = 0; i < th->splitPointsSize; ++i)
{
- SplitPoint& sp = Threads[i]->splitPoints[j];
+ SplitPoint& sp = th->splitPoints[i];
sp.mutex.lock();
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