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Do more extensions in nodes far from the root
Parameters found by @FauziAkram in the latest tune. Passed VVLTC w/ LTC Bound: LLR: 2.95 (-2.94,2.94) <0.50,2.50> Total: 243264 W: 63452 L: 62774 D: 117038 Ptnml(0-2): 18, 22494, 75934, 23164, 22 https://tests.stockfishchess.org/tests/view/680e82b23629b02d74b15e27 Passed VVLTC w/ STC Bound: LLR: 2.94 (-2.94,2.94) <0.00,2.00> Total: 37838 W: 9935 L: 9667 D: 18236 Ptnml(0-2): 6, 3383, 11873, 3651, 6 https://tests.stockfishchess.org/tests/view/681e707a3629b02d74b176e8 STC Elo Estimate: Elo: -0.49 ± 2.4 (95%) LOS: 34.8% Total: 20000 W: 5118 L: 5146 D: 9736 Ptnml(0-2): 55, 2365, 5182, 2349, 49 nElo: -0.96 ± 4.8 (95%) PairsRatio: 0.99 https://tests.stockfishchess.org/tests/view/6822af4b3629b02d74b17be6 closes https://github.com/official-stockfish/Stockfish/pull/6059 Bench: 2135382
This commit is contained in:
Shawn Xu
Disservin
114
src/search.cpp
114
src/search.cpp
@@ -1100,72 +1100,68 @@ moves_loop: // When in check, search starts here
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}
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// Step 15. Extensions
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// We take care to not overdo to avoid search getting stuck.
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if (ss->ply < thisThread->rootDepth * 2)
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// Singular extension search. If all moves but one
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// fail low on a search of (alpha-s, beta-s), and just one fails high on
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// (alpha, beta), then that move is singular and should be extended. To
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// verify this we do a reduced search on the position excluding the ttMove
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// and if the result is lower than ttValue minus a margin, then we will
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// extend the ttMove. Recursive singular search is avoided.
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// (*Scaler) Generally, higher singularBeta (i.e closer to ttValue)
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// and lower extension margins scale well.
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if (!rootNode && move == ttData.move && !excludedMove
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&& depth >= 6 - (thisThread->completedDepth > 27) + ss->ttPv && is_valid(ttData.value)
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&& !is_decisive(ttData.value) && (ttData.bound & BOUND_LOWER)
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&& ttData.depth >= depth - 3)
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{
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// Singular extension search. If all moves but one
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// fail low on a search of (alpha-s, beta-s), and just one fails high on
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// (alpha, beta), then that move is singular and should be extended. To
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// verify this we do a reduced search on the position excluding the ttMove
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// and if the result is lower than ttValue minus a margin, then we will
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// extend the ttMove. Recursive singular search is avoided.
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Value singularBeta = ttData.value - (58 + 76 * (ss->ttPv && !PvNode)) * depth / 57;
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Depth singularDepth = newDepth / 2;
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// (*Scaler) Generally, higher singularBeta (i.e closer to ttValue)
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// and lower extension margins scale well.
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ss->excludedMove = move;
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value = search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
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ss->excludedMove = Move::none();
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if (!rootNode && move == ttData.move && !excludedMove
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&& depth >= 6 - (thisThread->completedDepth > 27) + ss->ttPv
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&& is_valid(ttData.value) && !is_decisive(ttData.value)
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&& (ttData.bound & BOUND_LOWER) && ttData.depth >= depth - 3)
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if (value < singularBeta)
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{
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Value singularBeta = ttData.value - (58 + 76 * (ss->ttPv && !PvNode)) * depth / 57;
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Depth singularDepth = newDepth / 2;
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int corrValAdj1 = std::abs(correctionValue) / 248400;
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int corrValAdj2 = std::abs(correctionValue) / 249757;
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int doubleMargin = -4 + 244 * PvNode - 206 * !ttCapture - corrValAdj1
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- 997 * ttMoveHistory / 131072
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- (ss->ply * 2 > thisThread->rootDepth * 3) * 47;
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int tripleMargin = 84 + 269 * PvNode - 253 * !ttCapture + 91 * ss->ttPv
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- corrValAdj2 - (ss->ply * 2 > thisThread->rootDepth * 3) * 54;
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ss->excludedMove = move;
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value =
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search<NonPV>(pos, ss, singularBeta - 1, singularBeta, singularDepth, cutNode);
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ss->excludedMove = Move::none();
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extension =
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1 + (value < singularBeta - doubleMargin) + (value < singularBeta - tripleMargin);
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if (value < singularBeta)
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{
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int corrValAdj1 = std::abs(correctionValue) / 248400;
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int corrValAdj2 = std::abs(correctionValue) / 249757;
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int doubleMargin = -4 + 244 * PvNode - 206 * !ttCapture - corrValAdj1
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- 997 * ttMoveHistory / 131072;
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int tripleMargin =
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84 + 269 * PvNode - 253 * !ttCapture + 91 * ss->ttPv - corrValAdj2;
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extension = 1 + (value < singularBeta - doubleMargin)
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+ (value < singularBeta - tripleMargin);
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depth++;
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}
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// Multi-cut pruning
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// Our ttMove is assumed to fail high based on the bound of the TT entry,
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// and if after excluding the ttMove with a reduced search we fail high
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// over the original beta, we assume this expected cut-node is not
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// singular (multiple moves fail high), and we can prune the whole
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// subtree by returning a softbound.
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else if (value >= beta && !is_decisive(value))
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return value;
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// Negative extensions
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// If other moves failed high over (ttValue - margin) without the
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// ttMove on a reduced search, but we cannot do multi-cut because
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// (ttValue - margin) is lower than the original beta, we do not know
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// if the ttMove is singular or can do a multi-cut, so we reduce the
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// ttMove in favor of other moves based on some conditions:
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// If the ttMove is assumed to fail high over current beta
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else if (ttData.value >= beta)
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extension = -3;
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// If we are on a cutNode but the ttMove is not assumed to fail high
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// over current beta
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else if (cutNode)
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extension = -2;
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depth++;
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}
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// Multi-cut pruning
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// Our ttMove is assumed to fail high based on the bound of the TT entry,
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// and if after excluding the ttMove with a reduced search we fail high
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// over the original beta, we assume this expected cut-node is not
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// singular (multiple moves fail high), and we can prune the whole
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// subtree by returning a softbound.
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else if (value >= beta && !is_decisive(value))
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return value;
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// Negative extensions
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// If other moves failed high over (ttValue - margin) without the
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// ttMove on a reduced search, but we cannot do multi-cut because
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// (ttValue - margin) is lower than the original beta, we do not know
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// if the ttMove is singular or can do a multi-cut, so we reduce the
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// ttMove in favor of other moves based on some conditions:
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// If the ttMove is assumed to fail high over current beta
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else if (ttData.value >= beta)
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extension = -3;
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// If we are on a cutNode but the ttMove is not assumed to fail high
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// over current beta
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else if (cutNode)
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extension = -2;
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}
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// Step 16. Make the move
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