X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=3a80e161ff42238a3eb77c396e9a0feb80159fcc;hp=b87c689479d2a7909667a591d31c49b6b6cc21d4;hb=88de112b84a5285c2afb3e075a05c2ab8ad3fd33;hpb=a0486ecb40513db8141fa27c026f64771b8ebb55 diff --git a/src/search.cpp b/src/search.cpp index b87c6894..3a80e161 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -71,16 +71,6 @@ namespace { return Value((175 - 50 * improving) * d / ONE_PLY); } - // Margin for pruning capturing moves: almost linear in depth - constexpr int CapturePruneMargin[] = { 0, - 1 * PawnValueEg * 1055 / 1000, - 2 * PawnValueEg * 1042 / 1000, - 3 * PawnValueEg * 963 / 1000, - 4 * PawnValueEg * 1038 / 1000, - 5 * PawnValueEg * 950 / 1000, - 6 * PawnValueEg * 930 / 1000 - }; - // Futility and reductions lookup tables, initialized at startup int FutilityMoveCounts[2][16]; // [improving][depth] int Reductions[2][2][64][64]; // [pv][improving][depth][moveNumber] @@ -296,6 +286,7 @@ void Thread::search() { MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr); double timeReduction = 1.0; Color us = rootPos.side_to_move(); + bool failedLow; std::memset(ss-4, 0, 7 * sizeof(Stack)); for (int i = 4; i > 0; i--) @@ -305,7 +296,7 @@ void Thread::search() { beta = VALUE_INFINITE; if (mainThread) - mainThread->bestMoveChanges = 0, mainThread->failedLow = false; + mainThread->bestMoveChanges = 0, failedLow = false; size_t multiPV = Options["MultiPV"]; Skill skill(Options["Skill Level"]); @@ -346,7 +337,7 @@ void Thread::search() { // Age out PV variability metric if (mainThread) - mainThread->bestMoveChanges *= 0.517, mainThread->failedLow = false; + mainThread->bestMoveChanges *= 0.517, failedLow = false; // 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. @@ -423,7 +414,7 @@ void Thread::search() { if (mainThread) { - mainThread->failedLow = true; + failedLow = true; Threads.stopOnPonderhit = false; } } @@ -471,7 +462,7 @@ void Thread::search() { && !Threads.stop && !Threads.stopOnPonderhit) { - const int F[] = { mainThread->failedLow, + const int F[] = { failedLow, bestValue - mainThread->previousScore }; int improvingFactor = std::max(246, std::min(832, 306 + 119 * F[0] - 6 * F[1])); @@ -519,13 +510,25 @@ namespace { template Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) { - // Use quiescence search when needed - if (depth < ONE_PLY) - return qsearch(pos, ss, alpha, beta); - constexpr bool PvNode = NT == PV; const bool rootNode = PvNode && ss->ply == 0; + // Check if we have an upcoming move which draws by repetition, or + // if the opponent had an alternative move earlier to this position. + if ( pos.rule50_count() >= 3 + && alpha < VALUE_DRAW + && !rootNode + && pos.has_game_cycle(ss->ply)) + { + alpha = VALUE_DRAW; + if (alpha >= beta) + return alpha; + } + + // Dive into quiescence search when the depth reaches zero + if (depth < ONE_PLY) + return qsearch(pos, ss, alpha, beta); + assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE); assert(PvNode || (alpha == beta - 1)); assert(DEPTH_ZERO < depth && depth < DEPTH_MAX); @@ -578,17 +581,6 @@ namespace { beta = std::min(mate_in(ss->ply+1), beta); if (alpha >= beta) return alpha; - - // Check if there exists a move which draws by repetition, or an alternative - // earlier move to this position. - if ( pos.rule50_count() >= 3 - && alpha < VALUE_DRAW - && pos.has_game_cycle(ss->ply)) - { - alpha = VALUE_DRAW; - if (alpha >= beta) - return alpha; - } } assert(0 <= ss->ply && ss->ply < MAX_PLY); @@ -751,7 +743,7 @@ namespace { && ss->staticEval >= beta - 36 * depth / ONE_PLY + 225 && !excludedMove && pos.non_pawn_material(us) - && (ss->ply > thisThread->nmpMinPly || us != thisThread->nmpColor)) + && (ss->ply >= thisThread->nmpMinPly || us != thisThread->nmpColor)) { assert(eval - beta >= 0); @@ -780,7 +772,7 @@ namespace { // Do verification search at high depths, with null move pruning disabled // for us, until ply exceeds nmpMinPly. - thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4 - 1; + thisThread->nmpMinPly = ss->ply + 3 * (depth-R) / 4; thisThread->nmpColor = us; Value v = search(pos, ss, beta-1, beta, depth-R, false); @@ -961,7 +953,7 @@ moves_loop: // When in check, search starts from here } else if ( depth < 7 * ONE_PLY // (~20 Elo) && !extension - && !pos.see_ge(move, -Value(CapturePruneMargin[depth / ONE_PLY]))) + && !pos.see_ge(move, -Value(PawnValueEg * (depth / ONE_PLY)))) continue; } @@ -996,8 +988,7 @@ moves_loop: // When in check, search starts from here if (captureOrPromotion) // (~5 Elo) { // Increase reduction by comparing opponent's stat score - if ( (ss-1)->statScore >= 0 - && thisThread->captureHistory[movedPiece][to_sq(move)][type_of(pos.captured_piece())] < 0) + if ((ss-1)->statScore >= 0) r += ONE_PLY; r -= r ? ONE_PLY : DEPTH_ZERO; @@ -1164,9 +1155,10 @@ moves_loop: // When in check, search starts from here { // Quiet best move: update move sorting heuristics if (!pos.capture_or_promotion(bestMove)) - update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, stat_bonus(depth)); + update_quiet_stats(pos, ss, bestMove, quietsSearched, quietCount, + stat_bonus(depth + (bestValue > beta + PawnValueMg ? ONE_PLY : DEPTH_ZERO))); else - update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth)); + update_capture_stats(pos, bestMove, capturesSearched, captureCount, stat_bonus(depth + ONE_PLY)); // Extra penalty for a quiet TT move in previous ply when it gets refuted if ((ss-1)->moveCount == 1 && !pos.captured_piece())