X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fsearch.cpp;h=7f29f771c0a9eb3e05f8881502182c822e0f1e0f;hp=fe57806c7076198fee080a659dbd4d7161a5c46a;hb=353e20674b2019094059caaa3567e9a44abe9cd1;hpb=ff271093139de92ebf4f4f8b8c67474e07d6a8bf diff --git a/src/search.cpp b/src/search.cpp index fe57806c..7f29f771 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -61,8 +61,8 @@ namespace { // Different node types, used as a template parameter enum NodeType { NonPV, PV }; - constexpr uint64_t ttHitAverageWindow = 4096; - constexpr uint64_t ttHitAverageResolution = 1024; + constexpr uint64_t TtHitAverageWindow = 4096; + constexpr uint64_t TtHitAverageResolution = 1024; // Razor and futility margins constexpr int RazorMargin = 531; @@ -194,7 +194,7 @@ namespace { void Search::init() { for (int i = 1; i < MAX_MOVES; ++i) - Reductions[i] = int((24.8 + std::log(Threads.size()) / 2) * std::log(i)); + Reductions[i] = int((24.8 + std::log(Threads.size())) * std::log(i)); } @@ -280,7 +280,7 @@ void MainThread::search() { std::map votes; Value minScore = this->rootMoves[0].score; - // Find out minimum score + // Find minimum score for (Thread* th: Threads) minScore = std::min(minScore, th->rootMoves[0].score); @@ -290,19 +290,20 @@ void MainThread::search() { votes[th->rootMoves[0].pv[0]] += (th->rootMoves[0].score - minScore + 14) * int(th->completedDepth); - if (bestThread->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY) + if (abs(bestThread->rootMoves[0].score) >= VALUE_TB_WIN_IN_MAX_PLY) { - // Make sure we pick the shortest mate + // Make sure we pick the shortest mate / TB conversion or stave off mate the longest if (th->rootMoves[0].score > bestThread->rootMoves[0].score) bestThread = th; } else if ( th->rootMoves[0].score >= VALUE_TB_WIN_IN_MAX_PLY - || votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]]) + || ( th->rootMoves[0].score > VALUE_TB_LOSS_IN_MAX_PLY + && votes[th->rootMoves[0].pv[0]] > votes[bestThread->rootMoves[0].pv[0]])) bestThread = th; } } - previousScore = bestThread->rootMoves[0].score; + bestPreviousScore = bestThread->rootMoves[0].score; // Send again PV info if we have a new best thread if (bestThread != this) @@ -348,12 +349,12 @@ void Thread::search() { if (mainThread) { - if (mainThread->previousScore == VALUE_INFINITE) + if (mainThread->bestPreviousScore == VALUE_INFINITE) for (int i=0; i<4; ++i) mainThread->iterValue[i] = VALUE_ZERO; else for (int i=0; i<4; ++i) - mainThread->iterValue[i] = mainThread->previousScore; + mainThread->iterValue[i] = mainThread->bestPreviousScore; } size_t multiPV = Options["MultiPV"]; @@ -377,7 +378,7 @@ void Thread::search() { multiPV = std::max(multiPV, (size_t)4); multiPV = std::min(multiPV, rootMoves.size()); - ttHitAverage = ttHitAverageWindow * ttHitAverageResolution / 2; + ttHitAverage = TtHitAverageWindow * TtHitAverageResolution / 2; int ct = int(Options["Contempt"]) * PawnValueEg / 100; // From centipawns @@ -432,13 +433,13 @@ void Thread::search() { // Reset aspiration window starting size if (rootDepth >= 4) { - Value previousScore = rootMoves[pvIdx].previousScore; - delta = Value(21 + abs(previousScore) / 256); - alpha = std::max(previousScore - delta,-VALUE_INFINITE); - beta = std::min(previousScore + delta, VALUE_INFINITE); + Value prev = rootMoves[pvIdx].previousScore; + delta = Value(21); + alpha = std::max(prev - delta,-VALUE_INFINITE); + beta = std::min(prev + delta, VALUE_INFINITE); // Adjust contempt based on root move's previousScore (dynamic contempt) - int dct = ct + (102 - ct / 2) * previousScore / (abs(previousScore) + 157); + int dct = ct + (102 - ct / 2) * prev / (abs(prev) + 157); contempt = (us == WHITE ? make_score(dct, dct / 2) : -make_score(dct, dct / 2)); @@ -536,7 +537,7 @@ void Thread::search() { && !Threads.stop && !mainThread->stopOnPonderhit) { - double fallingEval = (332 + 6 * (mainThread->previousScore - bestValue) + double fallingEval = (332 + 6 * (mainThread->bestPreviousScore - bestValue) + 6 * (mainThread->iterValue[iterIdx] - bestValue)) / 704.0; fallingEval = Utility::clamp(fallingEval, 0.5, 1.5); @@ -625,14 +626,14 @@ namespace { Move ttMove, move, excludedMove, bestMove; Depth extension, newDepth; Value bestValue, value, ttValue, eval, maxValue; - bool ttHit, ttPv, inCheck, givesCheck, improving, didLMR, priorCapture; + bool ttHit, ttPv, formerPv, givesCheck, improving, didLMR, priorCapture; bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture, singularLMR; Piece movedPiece; int moveCount, captureCount, quietCount; // Step 1. Initialize node Thread* thisThread = pos.this_thread(); - inCheck = pos.checkers(); + ss->inCheck = pos.checkers(); priorCapture = pos.captured_piece(); Color us = pos.side_to_move(); moveCount = captureCount = quietCount = ss->moveCount = 0; @@ -653,7 +654,7 @@ namespace { if ( Threads.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) - return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) + return (ss->ply >= MAX_PLY && !ss->inCheck) ? evaluate(pos) : value_draw(pos.this_thread()); // Step 3. Mate distance pruning. Even if we mate at the next move our score @@ -695,13 +696,14 @@ namespace { ttMove = rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0] : ttHit ? tte->move() : MOVE_NONE; ttPv = PvNode || (ttHit && tte->is_pv()); + formerPv = ttPv && !PvNode; if (ttPv && depth > 12 && ss->ply - 1 < MAX_LPH && !pos.captured_piece() && is_ok((ss-1)->currentMove)) thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5); // thisThread->ttHitAverage can be used to approximate the running average of ttHit - thisThread->ttHitAverage = (ttHitAverageWindow - 1) * thisThread->ttHitAverage / ttHitAverageWindow - + ttHitAverageResolution * ttHit; + thisThread->ttHitAverage = (TtHitAverageWindow - 1) * thisThread->ttHitAverage / TtHitAverageWindow + + TtHitAverageResolution * ttHit; // At non-PV nodes we check for an early TT cutoff if ( !PvNode @@ -788,8 +790,10 @@ namespace { } } + CapturePieceToHistory& captureHistory = thisThread->captureHistory; + // Step 6. Static evaluation of the position - if (inCheck) + if (ss->inCheck) { ss->staticEval = eval = VALUE_NONE; improving = false; @@ -867,7 +871,7 @@ namespace { if (nullValue >= beta) { - // Do not return unproven mate scores + // Do not return unproven mate or TB scores if (nullValue >= VALUE_TB_WIN_IN_MAX_PLY) nullValue = beta; @@ -897,12 +901,16 @@ namespace { && depth >= 5 && abs(beta) < VALUE_TB_WIN_IN_MAX_PLY) { - Value raisedBeta = std::min(beta + 189 - 45 * improving, VALUE_INFINITE); - MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &thisThread->captureHistory); + Value raisedBeta = beta + 189 - 45 * improving; + assert(raisedBeta < VALUE_INFINITE); + MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory); int probCutCount = 0; - while ( (move = mp.next_move()) != MOVE_NONE - && probCutCount < 2 + 2 * cutNode) + while ( (move = mp.next_move()) != MOVE_NONE + && probCutCount < 2 + 2 * cutNode + && !( move == ttMove + && tte->depth() >= depth - 4 + && ttValue < raisedBeta)) if (move != excludedMove && pos.legal(move)) { assert(pos.capture_or_promotion(move)); @@ -912,7 +920,7 @@ namespace { probCutCount++; ss->currentMove = move; - ss->continuationHistory = &thisThread->continuationHistory[inCheck] + ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] [captureOrPromotion] [pos.moved_piece(move)] [to_sq(move)]; @@ -953,7 +961,7 @@ moves_loop: // When in check, search starts from here MovePicker mp(pos, ttMove, depth, &thisThread->mainHistory, &thisThread->lowPlyHistory, - &thisThread->captureHistory, + &captureHistory, contHist, countermove, ss->killers, @@ -1008,12 +1016,12 @@ moves_loop: // When in check, search starts from here // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold moveCountPruning = moveCount >= futility_move_count(improving, depth); + // Reduced depth of the next LMR search + int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0); + if ( !captureOrPromotion && !givesCheck) { - // Reduced depth of the next LMR search - int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0); - // Countermoves based pruning (~20 Elo) if ( lmrDepth < 4 + ((ss-1)->statScore > 0 || (ss-1)->moveCount == 1) && (*contHist[0])[movedPiece][to_sq(move)] < CounterMovePruneThreshold @@ -1022,7 +1030,7 @@ moves_loop: // When in check, search starts from here // Futility pruning: parent node (~5 Elo) if ( lmrDepth < 6 - && !inCheck + && !ss->inCheck && ss->staticEval + 235 + 172 * lmrDepth <= alpha && (*contHist[0])[movedPiece][to_sq(move)] + (*contHist[1])[movedPiece][to_sq(move)] @@ -1033,8 +1041,25 @@ moves_loop: // When in check, search starts from here if (!pos.see_ge(move, Value(-(32 - std::min(lmrDepth, 18)) * lmrDepth * lmrDepth))) continue; } - else if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo) - continue; + else + { + // Capture history based pruning when the move doesn't give check + if ( !givesCheck + && lmrDepth < 1 + && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0) + continue; + + // Futility pruning for captures + if ( !givesCheck + && lmrDepth < 6 + && !ss->inCheck + && ss->staticEval + 270 + 384 * lmrDepth + PieceValue[MG][type_of(pos.piece_on(to_sq(move)))] <= alpha) + continue; + + // See based pruning + if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo) + continue; + } } // Step 14. Extensions (~75 Elo) @@ -1054,10 +1079,10 @@ moves_loop: // When in check, search starts from here && tte->depth() >= depth - 3 && pos.legal(move)) { - Value singularBeta = ttValue - (((ttPv && !PvNode) + 4) * depth) / 2; - Depth halfDepth = depth / 2; + Value singularBeta = ttValue - ((formerPv + 4) * depth) / 2; + Depth singularDepth = (depth - 1 + 3 * formerPv) / 2; ss->excludedMove = move; - value = search(pos, ss, singularBeta - 1, singularBeta, halfDepth, cutNode); + value = search(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode); ss->excludedMove = MOVE_NONE; if (value < singularBeta) @@ -1073,6 +1098,18 @@ moves_loop: // When in check, search starts from here // a soft bound. else if (singularBeta >= beta) return singularBeta; + + // If the eval of ttMove is greater than beta we try also if there is an other move that + // pushes it over beta, if so also produce a cutoff + else if (ttValue >= beta) + { + ss->excludedMove = move; + value = search(pos, ss, beta - 1, beta, (depth + 3) / 2, cutNode); + ss->excludedMove = MOVE_NONE; + + if (value >= beta) + return beta; + } } // Check extension (~2 Elo) @@ -1095,6 +1132,12 @@ moves_loop: // When in check, search starts from here if (type_of(move) == CASTLING) extension = 1; + // Late irreversible move extension + if ( move == ttMove + && pos.rule50_count() > 80 + && (captureOrPromotion || type_of(movedPiece) == PAWN)) + extension = 2; + // Add extension to new depth newDepth += extension; @@ -1110,7 +1153,7 @@ moves_loop: // When in check, search starts from here // Update the current move (this must be done after singular extension search) ss->currentMove = move; - ss->continuationHistory = &thisThread->continuationHistory[inCheck] + ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] [captureOrPromotion] [movedPiece] [to_sq(move)]; @@ -1127,12 +1170,12 @@ moves_loop: // When in check, search starts from here || moveCountPruning || ss->staticEval + PieceValue[EG][pos.captured_piece()] <= alpha || cutNode - || thisThread->ttHitAverage < 375 * ttHitAverageResolution * ttHitAverageWindow / 1024)) + || thisThread->ttHitAverage < 375 * TtHitAverageResolution * TtHitAverageWindow / 1024)) { Depth r = reduction(improving, depth, moveCount); // Decrease reduction if the ttHit running average is large - if (thisThread->ttHitAverage > 500 * ttHitAverageResolution * ttHitAverageWindow / 1024) + if (thisThread->ttHitAverage > 500 * TtHitAverageResolution * TtHitAverageWindow / 1024) r--; // Reduction if other threads are searching this position. @@ -1143,13 +1186,16 @@ moves_loop: // When in check, search starts from here if (ttPv) r -= 2; + if (moveCountPruning && !formerPv) + r++; + // 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 (~3 Elo) if (singularLMR) - r -= 1 + (ttPv && !PvNode); + r -= 1 + formerPv; if (!captureOrPromotion) { @@ -1182,12 +1228,19 @@ moves_loop: // When in check, search starts from here r++; // Decrease/increase reduction for moves with a good/bad history (~30 Elo) - r -= ss->statScore / 16384; + r -= ss->statScore / 16434; + } + else + { + // Increase reduction for captures/promotions if late move and at low depth + if (depth < 8 && moveCount > 2) + r++; + + // Unless giving check, this capture is likely bad + if ( !givesCheck + && ss->staticEval + PieceValue[EG][pos.captured_piece()] + 200 * depth <= alpha) + r++; } - - // Increase reduction for captures/promotions if late move and at low depth - else if (depth < 8 && moveCount > 2) - r++; Depth d = Utility::clamp(newDepth - r, 1, newDepth); @@ -1319,11 +1372,11 @@ moves_loop: // When in check, search starts from here // must be a mate or a stalemate. If we are in a singular extension search then // return a fail low score. - assert(moveCount || !inCheck || excludedMove || !MoveList(pos).size()); + assert(moveCount || !ss->inCheck || excludedMove || !MoveList(pos).size()); if (!moveCount) bestValue = excludedMove ? alpha - : inCheck ? mated_in(ss->ply) : VALUE_DRAW; + : ss->inCheck ? mated_in(ss->ply) : VALUE_DRAW; else if (bestMove) update_all_stats(pos, ss, bestMove, bestValue, beta, prevSq, @@ -1367,7 +1420,7 @@ moves_loop: // When in check, search starts from here Move ttMove, move, bestMove; Depth ttDepth; Value bestValue, value, ttValue, futilityValue, futilityBase, oldAlpha; - bool ttHit, pvHit, inCheck, givesCheck, captureOrPromotion, evasionPrunable; + bool ttHit, pvHit, givesCheck, captureOrPromotion; int moveCount; if (PvNode) @@ -1380,20 +1433,20 @@ moves_loop: // When in check, search starts from here Thread* thisThread = pos.this_thread(); (ss+1)->ply = ss->ply + 1; bestMove = MOVE_NONE; - inCheck = pos.checkers(); + ss->inCheck = pos.checkers(); moveCount = 0; // Check for an immediate draw or maximum ply reached if ( pos.is_draw(ss->ply) || ss->ply >= MAX_PLY) - return (ss->ply >= MAX_PLY && !inCheck) ? evaluate(pos) : VALUE_DRAW; + return (ss->ply >= MAX_PLY && !ss->inCheck) ? evaluate(pos) : VALUE_DRAW; assert(0 <= ss->ply && ss->ply < MAX_PLY); // Decide whether or not to include checks: this fixes also the type of // TT entry depth that we are going to use. Note that in qsearch we use // only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS. - ttDepth = inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS + ttDepth = ss->inCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS : DEPTH_QS_NO_CHECKS; // Transposition table lookup posKey = pos.key(); @@ -1411,7 +1464,7 @@ moves_loop: // When in check, search starts from here return ttValue; // Evaluate the position statically - if (inCheck) + if (ss->inCheck) { ss->staticEval = VALUE_NONE; bestValue = futilityBase = -VALUE_INFINITE; @@ -1474,7 +1527,7 @@ moves_loop: // When in check, search starts from here moveCount++; // Futility pruning - if ( !inCheck + if ( !ss->inCheck && !givesCheck && futilityBase > -VALUE_KNOWN_WIN && !pos.advanced_pawn_push(move)) @@ -1496,14 +1549,8 @@ moves_loop: // When in check, search starts from here } } - // Detect non-capture evasions that are candidates to be pruned - evasionPrunable = inCheck - && (depth != 0 || moveCount > 2) - && bestValue > VALUE_TB_LOSS_IN_MAX_PLY - && !pos.capture(move); - // Don't search moves with negative SEE values - if ( (!inCheck || evasionPrunable) && !pos.see_ge(move)) + if ( !ss->inCheck && !pos.see_ge(move)) continue; // Speculative prefetch as early as possible @@ -1517,7 +1564,7 @@ moves_loop: // When in check, search starts from here } ss->currentMove = move; - ss->continuationHistory = &thisThread->continuationHistory[inCheck] + ss->continuationHistory = &thisThread->continuationHistory[ss->inCheck] [captureOrPromotion] [pos.moved_piece(move)] [to_sq(move)]; @@ -1551,7 +1598,7 @@ moves_loop: // When in check, search starts from here // All legal moves have been searched. A special case: If we're in check // and no legal moves were found, it is checkmate. - if (inCheck && bestValue == -VALUE_INFINITE) + if (ss->inCheck && bestValue == -VALUE_INFINITE) return mated_in(ss->ply); // Plies to mate from the root tte->save(posKey, value_to_tt(bestValue, ss->ply), pvHit, @@ -1670,8 +1717,12 @@ moves_loop: // When in check, search starts from here void update_continuation_histories(Stack* ss, Piece pc, Square to, int bonus) { for (int i : {1, 2, 4, 6}) + { + if (ss->inCheck && i > 2) + break; if (is_ok((ss-i)->currentMove)) (*(ss-i)->continuationHistory)[pc][to] << bonus; + } }