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Sometimes do a reduced search if LMR is skipped
If the node doesn't go through LMR and r is too big, reduce search depth by one ply. STC: LLR: 2.94 (-2.94,2.94) <0.00,2.00> Total: 664888 W: 176375 L: 175169 D: 313344 Ptnml(0-2): 1965, 73754, 179851, 74858, 2016 https://tests.stockfishchess.org/tests/view/6399414c93ed41c57ede8fb8 LTC: LLR: 2.94 (-2.94,2.94) <0.50,2.50> Total: 150784 W: 40553 L: 40031 D: 70200 Ptnml(0-2): 76, 14668, 45387, 15180, 81 https://tests.stockfishchess.org/tests/view/639dee6e11c576d919dc2b38 closes https://github.com/official-stockfish/Stockfish/pull/4290 Bench: 3727508
This commit is contained in:
Alfredo Menezes
Joost VandeVondele
parent
61ea1534ff
commit
c2d507005c
1 changed files with 48 additions and 48 deletions
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@ -1120,6 +1120,52 @@ moves_loop: // When in check, search starts here
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// Step 16. Make the move
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pos.do_move(move, st, givesCheck);
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Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);
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// Decrease reduction if position is or has been on the PV
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// and node is not likely to fail low. (~3 Elo)
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if ( ss->ttPv
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&& !likelyFailLow)
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r -= 2;
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// Decrease reduction if opponent's move count is high (~1 Elo)
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if ((ss-1)->moveCount > 7)
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r--;
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// Increase reduction for cut nodes (~3 Elo)
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if (cutNode)
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r += 2;
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// Increase reduction if ttMove is a capture (~3 Elo)
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if (ttCapture)
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r++;
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// Decrease reduction for PvNodes based on depth
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if (PvNode)
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r -= 1 + 11 / (3 + depth);
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// Decrease reduction if ttMove has been singularly extended (~1 Elo)
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if (singularQuietLMR)
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r--;
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// Decrease reduction if we move a threatened piece (~1 Elo)
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if ( depth > 9
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&& (mp.threatenedPieces & from_sq(move)))
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r--;
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// Increase reduction if next ply has a lot of fail high
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if ((ss+1)->cutoffCnt > 3)
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r++;
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ss->statScore = 2 * thisThread->mainHistory[us][from_to(move)]
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+ (*contHist[0])[movedPiece][to_sq(move)]
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+ (*contHist[1])[movedPiece][to_sq(move)]
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+ (*contHist[3])[movedPiece][to_sq(move)]
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- 4433;
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// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
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r -= ss->statScore / (13000 + 4152 * (depth > 7 && depth < 19));
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// Step 17. Late moves reduction / extension (LMR, ~98 Elo)
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// We use various heuristics for the sons of a node after the first son has
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// been searched. In general we would like to reduce them, but there are many
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@ -1130,52 +1176,6 @@ moves_loop: // When in check, search starts here
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|| !capture
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|| (cutNode && (ss-1)->moveCount > 1)))
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{
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Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);
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// Decrease reduction if position is or has been on the PV
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// and node is not likely to fail low. (~3 Elo)
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if ( ss->ttPv
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&& !likelyFailLow)
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r -= 2;
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// Decrease reduction if opponent's move count is high (~1 Elo)
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if ((ss-1)->moveCount > 7)
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r--;
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// Increase reduction for cut nodes (~3 Elo)
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if (cutNode)
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r += 2;
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// Increase reduction if ttMove is a capture (~3 Elo)
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if (ttCapture)
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r++;
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// Decrease reduction for PvNodes based on depth
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if (PvNode)
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r -= 1 + 11 / (3 + depth);
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// Decrease reduction if ttMove has been singularly extended (~1 Elo)
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if (singularQuietLMR)
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r--;
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// Decrease reduction if we move a threatened piece (~1 Elo)
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if ( depth > 9
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&& (mp.threatenedPieces & from_sq(move)))
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r--;
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// Increase reduction if next ply has a lot of fail high
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if ((ss+1)->cutoffCnt > 3)
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r++;
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ss->statScore = 2 * thisThread->mainHistory[us][from_to(move)]
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+ (*contHist[0])[movedPiece][to_sq(move)]
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+ (*contHist[1])[movedPiece][to_sq(move)]
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+ (*contHist[3])[movedPiece][to_sq(move)]
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- 4433;
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// Decrease/increase reduction for moves with a good/bad history (~30 Elo)
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r -= ss->statScore / (13000 + 4152 * (depth > 7 && depth < 19));
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// In general we want to cap the LMR depth search at newDepth, but when
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// reduction is negative, we allow this move a limited search extension
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// beyond the first move depth. This may lead to hidden double extensions.
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@ -1209,10 +1209,10 @@ moves_loop: // When in check, search starts here
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}
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}
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// Step 18. Full depth search when LMR is skipped
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// Step 18. Full depth search when LMR is skipped. If expected reduction is high, reduce its depth by 1.
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else if (!PvNode || moveCount > 1)
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{
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value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
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value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 4), !cutNode);
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}
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// For PV nodes only, do a full PV search on the first move or after a fail
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