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Revert "Mix alpha and statScore for reduction"

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This reverts commit 8bab09749d.

In this form the patch reduces mate finding effectiveness, as the large alpha value has negative influence on the reductions.

see also https://github.com/official-stockfish/Stockfish/pull/4183

Bench: 4114228
This commit is contained in:
Joost VandeVondele 2022-10-05 22:59:05 +02:00
parent 8bab09749d
commit da937e219e
1 changed files with 3 additions and 3 deletions
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6
src/search.cpp
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@ -787,9 +787,9 @@ namespace {
// The depth condition is important for mate finding. // The depth condition is important for mate finding.
if ( !ss->ttPv if ( !ss->ttPv
&& depth < 8 && depth < 8
&& eval - futility_margin(depth, improving) - (ss-1)->statScore / 301 >= beta && eval - futility_margin(depth, improving) - (ss-1)->statScore / 303 >= beta
&& eval >= beta && eval >= beta
&& eval < 28692) // larger than VALUE_KNOWN_WIN, but smaller than TB wins && eval < 28031) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
return eval; return eval;
// Step 9. Null move search with verification search (~22 Elo) // Step 9. Null move search with verification search (~22 Elo)
@ -1179,7 +1179,7 @@ moves_loop: // When in check, search starts here
- 4433; - 4433;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo) // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
r -= (ss->statScore + 5 * alpha) / 15448; r -= ss->statScore / 13628;
// In general we want to cap the LMR depth search at newDepth, but when // In general we want to cap the LMR depth search at newDepth, but when
// reduction is negative, we allow this move a limited search extension // reduction is negative, we allow this move a limited search extension