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Adjust LMR with correction history
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A positive constant increase in base reduction is applied to counter the
decrease in average reduction from this tweak.

Passed STC:
LLR: 2.98 (-2.94,2.94) <0.00,2.00>
Total: 109216 W: 28415 L: 27989 D: 52812
Ptnml(0-2): 310, 12848, 27911, 13184, 355
https://tests.stockfishchess.org/tests/view/6760bb0e86d5ee47d9542f26

Passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 66918 W: 17073 L: 16694 D: 33151
Ptnml(0-2): 33, 7175, 18666, 7550, 35
https://tests.stockfishchess.org/tests/view/6761e10f86d5ee47d95431fa

closes #5727

Bench: 1294909
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@xu-shawn @Disservin
xu-shawn authored and Disservin committed Dec 22, 2024
1 parent a04b072 commit e7e78aa
Showing 1 changed file with 22 additions and 18 deletions.
40 changes: 22 additions & 18 deletions src/search.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -77,25 +77,25 @@ constexpr int futility_move_count(bool improving, Depth depth) {
return (3 + depth * depth) / (2 - improving);
}

// Add correctionHistory value to raw staticEval and guarantee evaluation
// does not hit the tablebase range.
Value to_corrected_static_eval(Value v, const Worker& w, const Position& pos, Stack* ss) {
int correction_value(const Worker& w, const Position& pos, Stack* ss) {
const Color us = pos.side_to_move();
const auto m = (ss - 1)->currentMove;
const auto pcv = w.pawnCorrectionHistory[us][pawn_structure_index<Correction>(pos)];
const auto macv = w.majorPieceCorrectionHistory[us][major_piece_index(pos)];
const auto micv = w.minorPieceCorrectionHistory[us][minor_piece_index(pos)];
const auto wnpcv = w.nonPawnCorrectionHistory[WHITE][us][non_pawn_index<WHITE>(pos)];
const auto bnpcv = w.nonPawnCorrectionHistory[BLACK][us][non_pawn_index<BLACK>(pos)];
int cntcv = 1;
const auto cntcv =
m.is_ok() ? (*(ss - 2)->continuationCorrectionHistory)[pos.piece_on(m.to_sq())][m.to_sq()]
: 0;

if (m.is_ok())
cntcv = int((*(ss - 2)->continuationCorrectionHistory)[pos.piece_on(m.to_sq())][m.to_sq()]);
return (6384 * pcv + 3583 * macv + 6492 * micv + 6725 * (wnpcv + bnpcv) + 5880 * cntcv);
}

const auto cv =
(6384 * pcv + 3583 * macv + 6492 * micv + 6725 * (wnpcv + bnpcv) + cntcv * 5880) / 131072;
v += cv;
return std::clamp(v, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
// Add correctionHistory value to raw staticEval and guarantee evaluation
// does not hit the tablebase range.
Value to_corrected_static_eval(Value v, const int cv) {
return std::clamp(v + cv / 131072, VALUE_TB_LOSS_IN_MAX_PLY + 1, VALUE_TB_WIN_IN_MAX_PLY - 1);
}

// History and stats update bonus, based on depth
Expand Down Expand Up @@ -709,7 +709,8 @@ Value Search::Worker::search(
}

// Step 6. Static evaluation of the position
Value unadjustedStaticEval = VALUE_NONE;
Value unadjustedStaticEval = VALUE_NONE;
const auto correctionValue = correction_value(*thisThread, pos, ss);
if (ss->inCheck)
{
// Skip early pruning when in check
Expand All @@ -733,8 +734,7 @@ Value Search::Worker::search(
else if (PvNode)
Eval::NNUE::hint_common_parent_position(pos, networks[numaAccessToken], refreshTable);

ss->staticEval = eval =
to_corrected_static_eval(unadjustedStaticEval, *thisThread, pos, ss);
ss->staticEval = eval = to_corrected_static_eval(unadjustedStaticEval, correctionValue);

// ttValue can be used as a better position evaluation (~7 Elo)
if (is_valid(ttData.value)
Expand All @@ -744,8 +744,7 @@ Value Search::Worker::search(
else
{
unadjustedStaticEval = evaluate(pos);
ss->staticEval = eval =
to_corrected_static_eval(unadjustedStaticEval, *thisThread, pos, ss);
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(),
Expand Down Expand Up @@ -1155,6 +1154,10 @@ Value Search::Worker::search(

// These reduction adjustments have no proven non-linear scaling

r += 330;

r -= std::min(std::abs(correctionValue) / 32768, 2048);

// Increase reduction for cut nodes (~4 Elo)
if (cutNode)
r += 2518 - (ttData.depth >= depth && ss->ttPv) * 991;
Expand Down Expand Up @@ -1525,7 +1528,8 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta)
return ttData.value;

// Step 4. Static evaluation of the position
Value unadjustedStaticEval = VALUE_NONE;
Value unadjustedStaticEval = VALUE_NONE;
const auto correctionValue = correction_value(*thisThread, pos, ss);
if (ss->inCheck)
bestValue = futilityBase = -VALUE_INFINITE;
else
Expand All @@ -1537,7 +1541,7 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta)
if (!is_valid(unadjustedStaticEval))
unadjustedStaticEval = evaluate(pos);
ss->staticEval = bestValue =
to_corrected_static_eval(unadjustedStaticEval, *thisThread, pos, ss);
to_corrected_static_eval(unadjustedStaticEval, correctionValue);

// ttValue can be used as a better position evaluation (~13 Elo)
if (is_valid(ttData.value) && !is_decisive(ttData.value)
Expand All @@ -1550,7 +1554,7 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta)
unadjustedStaticEval =
(ss - 1)->currentMove != Move::null() ? evaluate(pos) : -(ss - 1)->staticEval;
ss->staticEval = bestValue =
to_corrected_static_eval(unadjustedStaticEval, *thisThread, pos, ss);
to_corrected_static_eval(unadjustedStaticEval, correctionValue);
}

// Stand pat. Return immediately if static value is at least beta
Expand Down

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