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8662bdf)
Drop useless condition
abs(ttValue) < VALUE_KNOWN_WIN
And extend singular extension search to cases when ttValue
stores a mate score. This improves mate finding and does
not introduce any regression.
Yery tested this patch against current master on the 6500+
Chest mate suite with 200K fixed nodes:
shortest mates found: master: 1206 patch:1205
any mate found: master: 1903 patch: 2003
with 1 sec time:
shortest mates found: master: 2667 patch: 2628
any mate found: master: 3585 patch: 3646
Verified for no regression:
STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 25655 W: 4578 L: 4465 D: 16612
LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 66247 W: 8618 L: 8557 D: 49072
bench:
6335042
singularExtensionNode = !rootNode
&& depth >= 8 * ONE_PLY
&& ttMove != MOVE_NONE
singularExtensionNode = !rootNode
&& depth >= 8 * ONE_PLY
&& ttMove != MOVE_NONE
- /* && ttValue != VALUE_NONE Already implicit in the next condition */
- && abs(ttValue) < VALUE_KNOWN_WIN
+ && ttValue != VALUE_NONE
&& !excludedMove // Recursive singular search is not allowed
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
&& !excludedMove // Recursive singular search is not allowed
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
&& !extension
&& pos.legal(move))
{
&& !extension
&& pos.legal(move))
{
- Value rBeta = ttValue - 2 * depth / ONE_PLY;
+ Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY;
ss->excludedMove = move;
ss->skipEarlyPruning = true;
Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY;
ss->excludedMove = move;
ss->skipEarlyPruning = true;