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remove two xors by setting the hash keys for unreachable squares to zero #5754

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remove two xors by setting the hash keys for unreachable squares to zero #5754

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bbfad96
remove two xors by setting the hash keys for unreachable squares to zero
ces42 Jan 7, 2025
c1626d5
Fix materialKey
ces42 Jan 27, 2025
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13 changes: 8 additions & 5 deletions src/position.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,9 @@ void Position::init() {
for (Piece pc : Pieces)
for (Square s = SQ_A1; s <= SQ_H8; ++s)
Zobrist::psq[pc][s] = rng.rand<Key>();
// pawns on these squares will promote
std::fill_n(Zobrist::psq[W_PAWN] + SQ_A8, 8, 0);
std::fill_n(Zobrist::psq[B_PAWN], 8, 0);

for (File f = FILE_A; f <= FILE_H; ++f)
Zobrist::enpassant[f] = rng.rand<Key>();
Expand Down Expand Up @@ -380,7 +383,7 @@ void Position::set_state() const {

for (Piece pc : Pieces)
for (int cnt = 0; cnt < pieceCount[pc]; ++cnt)
st->materialKey ^= Zobrist::psq[pc][cnt];
st->materialKey ^= Zobrist::psq[pc][8 + cnt];
}


Expand Down Expand Up @@ -780,7 +783,7 @@ void Position::do_move(Move m,
remove_piece(capsq);

k ^= Zobrist::psq[captured][capsq];
st->materialKey ^= Zobrist::psq[captured][pieceCount[captured]];
st->materialKey ^= Zobrist::psq[captured][8 + pieceCount[captured]];

// Reset rule 50 counter
st->rule50 = 0;
Expand Down Expand Up @@ -844,10 +847,10 @@ void Position::do_move(Move m,
dp.dirty_num++;

// Update hash keys
k ^= Zobrist::psq[pc][to] ^ Zobrist::psq[promotion][to];
st->pawnKey ^= Zobrist::psq[pc][to];
// Zobrist::psq[pc][to] is zero, so we don't need to clear it
k ^= Zobrist::psq[promotion][to];
st->materialKey ^=
Zobrist::psq[promotion][pieceCount[promotion] - 1] ^ Zobrist::psq[pc][pieceCount[pc]];
Zobrist::psq[promotion][8 + pieceCount[promotion] - 1] ^ Zobrist::psq[pc][8 + pieceCount[pc]];

if (promotionType <= BISHOP)
st->minorPieceKey ^= Zobrist::psq[promotion][to];
Expand Down
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