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Refine probcut

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Allow probcut for depth 3 and disable deeper verification search when it would simply repeat the qsearch.

Passed STC
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 283232 W: 74450 L: 73760 D: 135022
Ptnml(0-2): 1052, 33780, 71349, 34296, 1139
https://tests.stockfishchess.org/tests/view/67843b58460e2910c51ddcc6

Passed LTC
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 339654 W: 86845 L: 85893 D: 166916
Ptnml(0-2): 298, 37734, 92802, 38704, 289
https://tests.stockfishchess.org/tests/view/678aa722c00c743bc9e9face

closes https://github.com/official-stockfish/Stockfish/pull/5797

bench 1288648
This commit is contained in:
Daniel Monroe
2025-01-12 13:59:38 -08:00
committed by Joost VandeVondele
parent 738ac2a100
commit f00d91f8ac
1 changed files with 6 additions and 5 deletions
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src/search.cpp
+6 -5
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@@ -860,7 +860,7 @@ Value Search::Worker::search(
// If we have a good enough capture (or queen promotion) and a reduced search // If we have a good enough capture (or queen promotion) and a reduced search
// returns a value much above beta, we can (almost) safely prune the previous move. // returns a value much above beta, we can (almost) safely prune the previous move.
probCutBeta = beta + 174 - 56 * improving; probCutBeta = beta + 174 - 56 * improving;
if (depth > 3 if (depth >= 3
&& !is_decisive(beta) && !is_decisive(beta)
// If value from transposition table is lower than probCutBeta, don't attempt // If value from transposition table is lower than probCutBeta, don't attempt
// probCut there and in further interactions with transposition table cutoff // probCut there and in further interactions with transposition table cutoff
@@ -871,6 +871,7 @@ Value Search::Worker::search(
assert(probCutBeta < VALUE_INFINITE && probCutBeta > beta); assert(probCutBeta < VALUE_INFINITE && probCutBeta > beta);
MovePicker mp(pos, ttData.move, probCutBeta - ss->staticEval, &thisThread->captureHistory); MovePicker mp(pos, ttData.move, probCutBeta - ss->staticEval, &thisThread->captureHistory);
Depth probCutDepth = std::max(depth - 4, 0);
while ((move = mp.next_move()) != Move::none()) while ((move = mp.next_move()) != Move::none())
{ {
@@ -899,9 +900,9 @@ Value Search::Worker::search(
value = -qsearch<NonPV>(pos, ss + 1, -probCutBeta, -probCutBeta + 1); value = -qsearch<NonPV>(pos, ss + 1, -probCutBeta, -probCutBeta + 1);
// If the qsearch held, perform the regular search // If the qsearch held, perform the regular search
if (value >= probCutBeta) if (value >= probCutBeta && probCutDepth > 0)
value = value = -search<NonPV>(pos, ss + 1, -probCutBeta, -probCutBeta + 1, probCutDepth,
-search<NonPV>(pos, ss + 1, -probCutBeta, -probCutBeta + 1, depth - 4, !cutNode); !cutNode);
pos.undo_move(move); pos.undo_move(move);
@@ -909,7 +910,7 @@ Value Search::Worker::search(
{ {
// Save ProbCut data into transposition table // Save ProbCut data into transposition table
ttWriter.write(posKey, value_to_tt(value, ss->ply), ss->ttPv, BOUND_LOWER, ttWriter.write(posKey, value_to_tt(value, ss->ply), ss->ttPv, BOUND_LOWER,
depth - 3, move, unadjustedStaticEval, tt.generation()); probCutDepth + 1, move, unadjustedStaticEval, tt.generation());
if (!is_decisive(value)) if (!is_decisive(value))
return value - (probCutBeta - beta); return value - (probCutBeta - beta);