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Refactor: Simplify pawn structure indexing

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Refactoring the mechanism for calculating pawn structure hash indices and make it consistent with the rest.

closes https://github.com/official-stockfish/Stockfish/pull/6205

No functional change
This commit is contained in:
FauziAkram
2025-08-04 14:56:03 +02:00
committed by Joost VandeVondele
parent a6e34f128f
commit 8e733d68fd
3 changed files with 14 additions and 18 deletions
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src/history.h
+5 -7
View File
@@ -44,14 +44,12 @@ static_assert((PAWN_HISTORY_SIZE & (PAWN_HISTORY_SIZE - 1)) == 0,
static_assert((CORRECTION_HISTORY_SIZE & (CORRECTION_HISTORY_SIZE - 1)) == 0,
"CORRECTION_HISTORY_SIZE has to be a power of 2");
enum PawnHistoryType {
Normal,
Correction
};
inline int pawn_history_index(const Position& pos) {
return pos.pawn_key() & (PAWN_HISTORY_SIZE - 1);
}
template<PawnHistoryType T = Normal>
inline int pawn_structure_index(const Position& pos) {
return pos.pawn_key() & ((T == Normal ? PAWN_HISTORY_SIZE : CORRECTION_HISTORY_SIZE) - 1);
inline int pawn_correction_history_index(const Position& pos) {
return pos.pawn_key() & (CORRECTION_HISTORY_SIZE - 1);
}
inline int minor_piece_index(const Position& pos) {
src/movepick.cpp
+1 -1
View File
@@ -158,7 +158,7 @@ ExtMove* MovePicker::score(MoveList<Type>& ml) {
{
// histories
m.value = 2 * (*mainHistory)[us][m.from_to()];
m.value += 2 * (*pawnHistory)[pawn_structure_index(pos)][pc][to];
m.value += 2 * (*pawnHistory)[pawn_history_index(pos)][pc][to];
m.value += (*continuationHistory[0])[pc][to];
m.value += (*continuationHistory[1])[pc][to];
m.value += (*continuationHistory[2])[pc][to];
src/search.cpp
+8 -10
View File
@@ -75,7 +75,7 @@ using SearchedList = ValueList<Move, SEARCHEDLIST_CAPACITY>;
int correction_value(const Worker& w, const Position& pos, const Stack* const ss) {
const Color us = pos.side_to_move();
const auto m = (ss - 1)->currentMove;
const auto pcv = w.pawnCorrectionHistory[pawn_structure_index<Correction>(pos)][us];
const auto pcv = w.pawnCorrectionHistory[pawn_correction_history_index(pos)][us];
const auto micv = w.minorPieceCorrectionHistory[minor_piece_index(pos)][us];
const auto wnpcv = w.nonPawnCorrectionHistory[non_pawn_index<WHITE>(pos)][WHITE][us];
const auto bnpcv = w.nonPawnCorrectionHistory[non_pawn_index<BLACK>(pos)][BLACK][us];
@@ -101,8 +101,7 @@ void update_correction_history(const Position& pos,
static constexpr int nonPawnWeight = 165;
workerThread.pawnCorrectionHistory[pawn_structure_index<Correction>(pos)][us]
<< bonus * 128 / 128;
workerThread.pawnCorrectionHistory[pawn_correction_history_index(pos)][us] << bonus;
workerThread.minorPieceCorrectionHistory[minor_piece_index(pos)][us] << bonus * 153 / 128;
workerThread.nonPawnCorrectionHistory[non_pawn_index<WHITE>(pos)][WHITE][us]
<< bonus * nonPawnWeight / 128;
@@ -815,7 +814,7 @@ Value Search::Worker::search(
mainHistory[~us][((ss - 1)->currentMove).from_to()] << bonus * 935 / 1024;
if (!ttHit && type_of(pos.piece_on(prevSq)) != PAWN
&& ((ss - 1)->currentMove).type_of() != PROMOTION)
pawnHistory[pawn_structure_index(pos)][pos.piece_on(prevSq)][prevSq]
pawnHistory[pawn_history_index(pos)][pos.piece_on(prevSq)][prevSq]
<< bonus * 1428 / 1024;
}
@@ -823,8 +822,7 @@ Value Search::Worker::search(
// 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.
improving = ss->staticEval > (ss - 2)->staticEval;
improving = ss->staticEval > (ss - 2)->staticEval;
opponentWorsening = ss->staticEval > -(ss - 1)->staticEval;
if (priorReduction >= (depth < 10 ? 1 : 3) && !opponentWorsening)
@@ -1069,7 +1067,7 @@ moves_loop: // When in check, search starts here
{
int history = (*contHist[0])[movedPiece][move.to_sq()]
+ (*contHist[1])[movedPiece][move.to_sq()]
+ pawnHistory[pawn_structure_index(pos)][movedPiece][move.to_sq()];
+ pawnHistory[pawn_history_index(pos)][movedPiece][move.to_sq()];
// Continuation history based pruning
if (history < -4361 * depth)
@@ -1423,7 +1421,7 @@ moves_loop: // When in check, search starts here
mainHistory[~us][((ss - 1)->currentMove).from_to()] << scaledBonus * 224 / 32768;
if (type_of(pos.piece_on(prevSq)) != PAWN && ((ss - 1)->currentMove).type_of() != PROMOTION)
pawnHistory[pawn_structure_index(pos)][pos.piece_on(prevSq)][prevSq]
pawnHistory[pawn_history_index(pos)][pos.piece_on(prevSq)][prevSq]
<< scaledBonus * 1127 / 32768;
}
@@ -1642,7 +1640,7 @@ Value Search::Worker::qsearch(Position& pos, Stack* ss, Value alpha, Value beta)
// Continuation history based pruning
if (!capture
&& (*contHist[0])[pos.moved_piece(move)][move.to_sq()]
+ pawnHistory[pawn_structure_index(pos)][pos.moved_piece(move)][move.to_sq()]
+ pawnHistory[pawn_history_index(pos)][pos.moved_piece(move)][move.to_sq()]
<= 5868)
continue;
@@ -1879,7 +1877,7 @@ void update_quiet_histories(
update_continuation_histories(ss, pos.moved_piece(move), move.to_sq(),
bonus * (bonus > 0 ? 979 : 842) / 1024);
int pIndex = pawn_structure_index(pos);
int pIndex = pawn_history_index(pos);
workerThread.pawnHistory[pIndex][pos.moved_piece(move)][move.to_sq()]
<< (bonus * (bonus > 0 ? 704 : 439) / 1024) + 70;
}