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
+ Copyright (C) 2015-2020 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
void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus);
void update_quiet_stats(const Position& pos, Stack* ss, Move move, int bonus);
void update_all_stats(const Position& pos, Stack* ss, Move bestMove, Value bestValue, Value beta, Square prevSq,
- Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth);
+ Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth, bool pastPV);
// perft() is our utility to verify move generation. All the leaf nodes up
// to the given depth are generated and counted, and the sum is returned.
contempt = (us == WHITE ? make_score(ct, ct / 2)
: -make_score(ct, ct / 2));
+ int searchAgainCounter = 0;
+
// Iterative deepening loop until requested to stop or the target depth is reached
while ( ++rootDepth < MAX_PLY
&& !Threads.stop
size_t pvFirst = 0;
pvLast = 0;
+ if (!Threads.increaseDepth)
+ searchAgainCounter++;
+
// MultiPV loop. We perform a full root search for each PV line
for (pvIdx = 0; pvIdx < multiPV && !Threads.stop; ++pvIdx)
{
int failedHighCnt = 0;
while (true)
{
- Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt);
+ Depth adjustedDepth = std::max(1, rootDepth - failedHighCnt - searchAgainCounter);
bestValue = ::search<PV>(rootPos, ss, alpha, beta, adjustedDepth, false);
// Bring the best move to the front. It is critical that sorting
else
Threads.stop = true;
}
+ else if ( Threads.increaseDepth
+ && !mainThread->ponder
+ && Time.elapsed() > Time.optimum() * fallingEval * reduction * bestMoveInstability * 0.6)
+ Threads.increaseDepth = false;
+ else
+ Threads.increaseDepth = true;
}
mainThread->iterValue[iterIdx] = bestValue;
if (ttValue >= beta)
{
if (!pos.capture_or_promotion(ttMove))
- update_quiet_stats(pos, ss, ttMove, stat_bonus(depth));
+ update_quiet_stats(pos, ss, ttMove, stat_bonus(depth + (!PvNode && ttPv)));
// Extra penalty for early quiet moves of the previous ply
if ((ss-1)->moveCount <= 2 && !priorCapture)
// Penalty for a quiet ttMove that fails low
else if (!pos.capture_or_promotion(ttMove))
{
- int penalty = -stat_bonus(depth);
+ int penalty = -stat_bonus(depth + (!PvNode && ttPv));
thisThread->mainHistory[us][from_to(ttMove)] << penalty;
update_continuation_histories(ss, pos.moved_piece(ttMove), to_sq(ttMove), penalty);
}
}
- return ttValue;
+
+ if (pos.rule50_count() < 90)
+ return ttValue;
}
// Step 5. Tablebases probe
tte->save(posKey, VALUE_NONE, ttPv, BOUND_NONE, DEPTH_NONE, MOVE_NONE, eval);
}
- // Step 7. Razoring (~2 Elo)
+ // Step 7. Razoring (~1 Elo)
if ( !rootNode // The required rootNode PV handling is not available in qsearch
&& depth < 2
&& eval <= alpha - RazorMargin)
return qsearch<NT>(pos, ss, alpha, beta);
- improving = (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval >= (ss-4)->staticEval
- || (ss-4)->staticEval == VALUE_NONE) : ss->staticEval >= (ss-2)->staticEval;
+ improving = (ss-2)->staticEval == VALUE_NONE ? (ss->staticEval > (ss-4)->staticEval
+ || (ss-4)->staticEval == VALUE_NONE) : ss->staticEval > (ss-2)->staticEval;
- // Step 8. Futility pruning: child node (~30 Elo)
+ // Step 8. Futility pruning: child node (~50 Elo)
if ( !PvNode
&& depth < 6
&& eval - futility_margin(depth, improving) >= beta
// Step 9. Null move search with verification search (~40 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
- && (ss-1)->statScore < 23405
+ && (ss-1)->statScore < 23397
&& eval >= beta
&& eval >= ss->staticEval
- && ss->staticEval >= beta - 32 * depth + 317 - improving * 30
+ && ss->staticEval >= beta - 32 * depth - 30 * improving + 120 * ttPv + 292
&& !excludedMove
&& pos.non_pawn_material(us)
&& (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor))
}
}
- // Step 11. Internal iterative deepening (~2 Elo)
+ // Step 11. Internal iterative deepening (~1 Elo)
if (depth >= 7 && !ttMove)
{
search<NT>(pos, ss, alpha, beta, depth - 7, cutNode);
// Calculate new depth for this move
newDepth = depth - 1;
- // Step 13. Pruning at shallow depth (~170 Elo)
+ // Step 13. Pruning at shallow depth (~200 Elo)
if ( !rootNode
&& pos.non_pawn_material(us)
&& bestValue > VALUE_MATED_IN_MAX_PLY)
&& (*contHist[1])[movedPiece][to_sq(move)] < CounterMovePruneThreshold)
continue;
- // Futility pruning: parent node (~2 Elo)
+ // Futility pruning: parent node (~5 Elo)
if ( lmrDepth < 6
&& !inCheck
- && ss->staticEval + 255 + 182 * lmrDepth <= alpha
+ && ss->staticEval + 235 + 172 * lmrDepth <= alpha
&& thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)]
+ (*contHist[1])[movedPiece][to_sq(move)]
- + (*contHist[3])[movedPiece][to_sq(move)] < 30000)
+ + (*contHist[3])[movedPiece][to_sq(move)] < 25000)
continue;
- // Prune moves with negative SEE (~10 Elo)
+ // Prune moves with negative SEE (~20 Elo)
if (!pos.see_ge(move, Value(-(32 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth)))
continue;
}
- else if (!pos.see_ge(move, Value(-194) * depth)) // (~20 Elo)
- continue;
+ else if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo)
+ {
+ if (captureOrPromotion && captureCount < 32)
+ capturesSearched[captureCount++] = move;
+ continue;
+ }
}
- // Step 14. Extensions (~70 Elo)
+ // Step 14. Extensions (~75 Elo)
- // Singular extension search (~60 Elo). If all moves but one fail low on a
+ // Singular extension search (~70 Elo). If all moves but one fail low on a
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
// then that move is singular and should be extended. To verify this we do
// a reduced search on all the other moves but the ttMove and if the
// Step 15. Make the move
pos.do_move(move, st, givesCheck);
- // Step 16. Reduced depth search (LMR). If the move fails high it will be
+ // Step 16. Reduced depth search (LMR, ~200 Elo). If the move fails high it will be
// re-searched at full depth.
if ( depth >= 3
- && moveCount > 1 + 2 * rootNode
+ && moveCount > 1 + rootNode + (rootNode && bestValue < alpha)
&& (!rootNode || thisThread->best_move_count(move) == 0)
&& ( !captureOrPromotion
|| moveCountPruning
if (th.marked())
r++;
- // Decrease reduction if position is or has been on the PV
+ // Decrease reduction if position is or has been on the PV (~10 Elo)
if (ttPv)
r -= 2;
- // Decrease reduction if opponent's move count is high (~10 Elo)
+ // Decrease reduction if opponent's move count is high (~5 Elo)
if ((ss-1)->moveCount > 14)
r--;
- // Decrease reduction if ttMove has been singularly extended
+ // Decrease reduction if ttMove has been singularly extended (~3 Elo)
if (singularLMR)
r -= 2;
if (!captureOrPromotion)
{
- // Increase reduction if ttMove is a capture (~0 Elo)
+ // Increase reduction if ttMove is a capture (~5 Elo)
if (ttCapture)
r++;
- // Increase reduction for cut nodes (~5 Elo)
+ // Increase reduction for cut nodes (~10 Elo)
if (cutNode)
r += 2;
// Decrease reduction for moves that escape a capture. Filter out
// castling moves, because they are coded as "king captures rook" and
- // hence break make_move(). (~5 Elo)
+ // hence break make_move(). (~2 Elo)
else if ( type_of(move) == NORMAL
&& !pos.see_ge(reverse_move(move)))
- r -= 2;
+ r -= 2 + ttPv;
ss->statScore = thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)]
r -= ss->statScore / 16384;
}
+ // Increase reduction for captures/promotions if late move and at low depth
+ else if (depth < 8 && moveCount > 2)
+ r++;
+
Depth d = clamp(newDepth - r, 1, newDepth);
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
else if (bestMove)
update_all_stats(pos, ss, bestMove, bestValue, beta, prevSq,
- quietsSearched, quietCount, capturesSearched, captureCount, depth);
+ quietsSearched, quietCount, capturesSearched, captureCount, depth, (!PvNode && ttPv));
// Bonus for prior countermove that caused the fail low
else if ( (depth >= 3 || PvNode)
// update_all_stats() updates stats at the end of search() when a bestMove is found
void update_all_stats(const Position& pos, Stack* ss, Move bestMove, Value bestValue, Value beta, Square prevSq,
- Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth) {
+ Move* quietsSearched, int quietCount, Move* capturesSearched, int captureCount, Depth depth, bool pastPV) {
int bonus1, bonus2;
Color us = pos.side_to_move();
PieceType captured = type_of(pos.piece_on(to_sq(bestMove)));
bonus1 = stat_bonus(depth + 1);
- bonus2 = bestValue > beta + PawnValueMg ? bonus1 // larger bonus
- : stat_bonus(depth); // smaller bonus
+ bonus2 = pastPV || bestValue > beta + PawnValueMg ? bonus1 // larger bonus
+ : stat_bonus(depth); // smaller bonus
if (!pos.capture_or_promotion(bestMove))
{
projects / stockfish / blobdiff