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Move hindsight reductions above cutoffs

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Passed STC
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 52640 W: 13701 L: 13361 D: 25578
Ptnml(0-2): 168, 6143, 13356, 6487, 166
https://tests.stockfishchess.org/tests/view/6918dc407ca8781852332339

Passed LTC
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 207690 W: 53187 L: 52520 D: 101983
Ptnml(0-2): 93, 22515, 57994, 23118, 125
https://tests.stockfishchess.org/tests/view/6919dd307ca87818523324c7

closes https://github.com/official-stockfish/Stockfish/pull/6448

Bench: 2912398
This commit is contained in:
Daniel Monroe
2025-12-01 17:35:34 +01:00
committed by Joost VandeVondele
parent abd835dcbc
commit 5297ba0a1a
1 changed files with 50 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/search.cpp
+50 -48
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@@ -702,6 +702,56 @@ Value Search::Worker::search(
// At this point, if excluded, skip straight to step 6, static eval. However,
// to save indentation, we list the condition in all code between here and there.
// Step 6. Static evaluation of the position
Value unadjustedStaticEval = VALUE_NONE;
const auto correctionValue = correction_value(*this, pos, ss);
if (ss->inCheck)
{
// Skip early pruning when in check
ss->staticEval = eval = (ss - 2)->staticEval;
improving = false;
}
else if (excludedMove)
unadjustedStaticEval = eval = ss->staticEval;
else if (ss->ttHit)
{
// Never assume anything about values stored in TT
unadjustedStaticEval = ttData.eval;
if (!is_valid(unadjustedStaticEval))
unadjustedStaticEval = evaluate(pos);
ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
// ttValue can be used as a better position evaluation
if (is_valid(ttData.value)
&& (ttData.bound & (ttData.value > eval ? BOUND_LOWER : BOUND_UPPER)))
eval = ttData.value;
}
else
{
unadjustedStaticEval = evaluate(pos);
ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
// Static evaluation is saved as it was before adjustment by correction history
ttWriter.write(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_UNSEARCHED, Move::none(),
unadjustedStaticEval, tt.generation());
}
// Set up the improving flag, which is true if current static evaluation is
// bigger than the previous static evaluation at our turn (if we were in
// check at our previous move we go back until we weren't in check) and is
// false otherwise. The improving flag is used in various pruning heuristics.
// Similarly, opponentWorsening is true if our static evaluation is better
// for us than at the last ply.
improving = ss->staticEval > (ss - 2)->staticEval;
opponentWorsening = ss->staticEval > -(ss - 1)->staticEval;
// Hindsight adjustment of reductions based on static evaluation difference.
if (priorReduction >= 3 && !opponentWorsening)
depth++;
if (priorReduction >= 2 && depth >= 2 && ss->staticEval + (ss - 1)->staticEval > 173)
depth--;
// At non-PV nodes we check for an early TT cutoff
if (!PvNode && !excludedMove && ttData.depth > depth - (ttData.value <= beta)
&& is_valid(ttData.value) // Can happen when !ttHit or when access race in probe()
@@ -799,41 +849,8 @@ Value Search::Worker::search(
}
}
// Step 6. Static evaluation of the position
Value unadjustedStaticEval = VALUE_NONE;
const auto correctionValue = correction_value(*this, pos, ss);
if (ss->inCheck)
{
// Skip early pruning when in check
ss->staticEval = eval = (ss - 2)->staticEval;
improving = false;
goto moves_loop;
}
else if (excludedMove)
unadjustedStaticEval = eval = ss->staticEval;
else if (ss->ttHit)
{
// Never assume anything about values stored in TT
unadjustedStaticEval = ttData.eval;
if (!is_valid(unadjustedStaticEval))
unadjustedStaticEval = evaluate(pos);
ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
// ttValue can be used as a better position evaluation
if (is_valid(ttData.value)
&& (ttData.bound & (ttData.value > eval ? BOUND_LOWER : BOUND_UPPER)))
eval = ttData.value;
}
else
{
unadjustedStaticEval = evaluate(pos);
ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);
// Static evaluation is saved as it was before adjustment by correction history
ttWriter.write(posKey, VALUE_NONE, ss->ttPv, BOUND_NONE, DEPTH_UNSEARCHED, Move::none(),
unadjustedStaticEval, tt.generation());
}
// Use static evaluation difference to improve quiet move ordering
if (((ss - 1)->currentMove).is_ok() && !(ss - 1)->inCheck && !priorCapture)
@@ -845,21 +862,6 @@ Value Search::Worker::search(
pawnHistory[pawn_history_index(pos)][pos.piece_on(prevSq)][prevSq] << evalDiff * 13;
}
// Set up the improving flag, which is true if current static evaluation is
// bigger than the previous static evaluation at our turn (if we were in
// check at our previous move we go back until we weren't in check) and is
// false otherwise. The improving flag is used in various pruning heuristics.
// Similarly, opponentWorsening is true if our static evaluation is better
// for us than at the last ply.
improving = ss->staticEval > (ss - 2)->staticEval;
opponentWorsening = ss->staticEval > -(ss - 1)->staticEval;
// Hindsight adjustment of reductions based on static evaluation difference.
if (priorReduction >= 3 && !opponentWorsening)
depth++;
if (priorReduction >= 2 && depth >= 2 && ss->staticEval + (ss - 1)->staticEval > 169)
depth--;
// Step 7. Razoring
// If eval is really low, skip search entirely and return the qsearch value.