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Adjust usage of history in futility pruning
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This patch refines 0ac8aca that uses history heuristics in futility pruning.
Now it adds main history of the move to in and also increases effect by factor of 2.

passed STC
https://tests.stockfishchess.org/tests/view/61a156829e83391467a2b2c9
LLR: 2.94 (-2.94,2.94) <0.00,2.50>
Total: 68464 W: 17920 L: 17587 D: 32957
Ptnml(0-2): 239, 7711, 18025, 7992, 265

passed LTC
https://tests.stockfishchess.org/tests/view/61a1bde99e83391467a2b305
LLR: 2.95 (-2.94,2.94) <0.50,3.00>
Total: 26088 W: 6926 L: 6674 D: 12488
Ptnml(0-2): 18, 2619, 7531, 2845, 31

closes #3812

bench 6804653
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Vizvezdenec authored and vondele committed Nov 27, 2021
1 parent 4bb11e8 commit 8bb5a43
Showing 1 changed file with 3 additions and 1 deletion.
4 changes: 3 additions & 1 deletion src/search.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1063,10 +1063,12 @@ namespace {
&& history < -3000 * depth + 3000)
continue;

history += thisThread->mainHistory[us][from_to(move)];

// Futility pruning: parent node (~5 Elo)
if ( !ss->inCheck
&& lmrDepth < 8
&& ss->staticEval + 172 + 145 * lmrDepth + history / 256 <= alpha)
&& ss->staticEval + 172 + 145 * lmrDepth + history / 128 <= alpha)
continue;

// Prune moves with negative SEE (~20 Elo)
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