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Introduce pawn structure based history

Browse Source 
Original idea by Seer chess engine https://github.com/connormcmonigle/seer-nnue,
coding done by @Disservin, code refactoring done by @locutus2 to match the style
of other histories.

This patch introduces pawn structure based history, which assings moves values
based on last digits of pawn structure hash and piece type of moved piece and
landing square of the move. Idea is that good places for pieces are quite often
determined by pawn structure of position. Used in 3 different places
- sorting of quiet moves, sorting of quiet check evasions and in history based
pruning in search.

Passed STC:
https://tests.stockfishchess.org/tests/view/65391d08cc309ae83955dbaf
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 155488 W: 39408 L: 38913 D: 77167
Ptnml(0-2): 500, 18427, 39408, 18896, 513

Passed LTC:
https://tests.stockfishchess.org/tests/view/653a36a2cc309ae83955f181
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 70110 W: 17548 L: 17155 D: 35407
Ptnml(0-2): 33, 7859, 18889, 8230, 44

closes https://github.com/official-stockfish/Stockfish/pull/4849

Bench: 1257882

Co-Authored-By: Disservin <disservin.social@gmail.com>
Co-Authored-By: Stefan Geschwentner <locutus2@users.noreply.github.com>
This commit is contained in:
Michael Chaly
2023-10-27 17:19:31 +02:00
committed by Disservin
parent 871ab55f01
commit b0658f09b9
7 changed files with 53 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/position.cpp
+14 -3
View File
@@ -49,7 +49,7 @@ namespace Zobrist {
Key psq[PIECE_NB][SQUARE_NB];
Key enpassant[FILE_NB];
Key castling[CASTLING_RIGHT_NB];
Key side;
Key side, noPawns;
}
namespace {
@@ -128,7 +128,8 @@ void Position::init() {
for (int cr = NO_CASTLING; cr <= ANY_CASTLING; ++cr)
Zobrist::castling[cr] = rng.rand<Key>();
Zobrist::side = rng.rand<Key>();
Zobrist::side = rng.rand<Key>();
Zobrist::noPawns = rng.rand<Key>();
// Prepare the cuckoo tables
std::memset(cuckoo, 0, sizeof(cuckoo));
@@ -337,6 +338,7 @@ void Position::set_check_info() const {
void Position::set_state() const {
st->key = st->materialKey = 0;
st->pawnKey = Zobrist::noPawns;
st->nonPawnMaterial[WHITE] = st->nonPawnMaterial[BLACK] = VALUE_ZERO;
st->checkersBB = attackers_to(square<KING>(sideToMove)) & pieces(~sideToMove);
@@ -348,7 +350,10 @@ void Position::set_state() const {
Piece pc = piece_on(s);
st->key ^= Zobrist::psq[pc][s];
if (type_of(pc) != KING && type_of(pc) != PAWN)
if (type_of(pc) == PAWN)
st->pawnKey ^= Zobrist::psq[pc][s];
else if (type_of(pc) != KING)
st->nonPawnMaterial[color_of(pc)] += PieceValue[pc];
}
@@ -728,6 +733,8 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
assert(piece_on(to) == NO_PIECE);
assert(piece_on(capsq) == make_piece(them, PAWN));
}
st->pawnKey ^= Zobrist::psq[captured][capsq];
}
else
st->nonPawnMaterial[them] -= PieceValue[captured];
@@ -806,6 +813,7 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
// Update hash keys
k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[promotion][to];
st->pawnKey ^= Zobrist::psq[pc][to];
st->materialKey ^=
Zobrist::psq[promotion][pieceCount[promotion] - 1] ^ Zobrist::psq[pc][pieceCount[pc]];
@@ -813,6 +821,9 @@ void Position::do_move(Move m, StateInfo& newSt, bool givesCheck) {
st->nonPawnMaterial[us] += PieceValue[promotion];
}
// Update pawn hash key
st->pawnKey ^= Zobrist::psq[pc][from] ^ Zobrist::psq[pc][to];
// Reset rule 50 draw counter
st->rule50 = 0;
}