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Init threat offsets at compile time

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Init threat offsets at compile time. Avoid another global init function call.

Passed STC Non-Regression:
https://tests.stockfishchess.org/tests/view/694971a83c8768ca4507275c
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 43296 W: 11284 L: 11077 D: 20935
Ptnml(0-2): 152, 4611, 11924, 4800, 161

closes https://github.com/official-stockfish/Stockfish/pull/6487

No functional change
This commit is contained in:
Disservin
2025-12-23 21:42:45 +01:00
parent 4d4c6ebd02
commit 73b3b18595
6 changed files with 293 additions and 173 deletions
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src/bitboard.cpp
+2 -46
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@@ -32,7 +32,6 @@ uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
Bitboard LineBB[SQUARE_NB][SQUARE_NB];
Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
Bitboard RayPassBB[SQUARE_NB][SQUARE_NB];
Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
alignas(64) Magic Magics[SQUARE_NB][2];
@@ -42,13 +41,6 @@ Bitboard RookTable[0x19000]; // To store rook attacks
Bitboard BishopTable[0x1480]; // To store bishop attacks
void init_magics(PieceType pt, Bitboard table[], Magic magics[][2]);
// Returns the bitboard of target square for the given step
// from the given square. If the step is off the board, returns empty bitboard.
Bitboard safe_destination(Square s, int step) {
Square to = Square(s + step);
return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
}
}
// Returns an ASCII representation of a bitboard suitable
@@ -86,18 +78,6 @@ void Bitboards::init() {
for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
{
PseudoAttacks[WHITE][s1] = pawn_attacks_bb<WHITE>(square_bb(s1));
PseudoAttacks[BLACK][s1] = pawn_attacks_bb<BLACK>(square_bb(s1));
for (int step : {-9, -8, -7, -1, 1, 7, 8, 9})
PseudoAttacks[KING][s1] |= safe_destination(s1, step);
for (int step : {-17, -15, -10, -6, 6, 10, 15, 17})
PseudoAttacks[KNIGHT][s1] |= safe_destination(s1, step);
PseudoAttacks[QUEEN][s1] = PseudoAttacks[BISHOP][s1] = attacks_bb<BISHOP>(s1, 0);
PseudoAttacks[QUEEN][s1] |= PseudoAttacks[ROOK][s1] = attacks_bb<ROOK>(s1, 0);
for (PieceType pt : {BISHOP, ROOK})
for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
{
@@ -115,30 +95,6 @@ void Bitboards::init() {
}
namespace {
Bitboard sliding_attack(PieceType pt, Square sq, Bitboard occupied) {
Bitboard attacks = 0;
Direction RookDirections[4] = {NORTH, SOUTH, EAST, WEST};
Direction BishopDirections[4] = {NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST};
for (Direction d : (pt == ROOK ? RookDirections : BishopDirections))
{
Square s = sq;
while (safe_destination(s, d))
{
attacks |= (s += d);
if (occupied & s)
{
break;
}
}
}
return attacks;
}
// Computes all rook and bishop attacks at startup. Magic
// bitboards are used to look up attacks of sliding pieces. As a reference see
// https://www.chessprogramming.org/Magic_Bitboards. In particular, here we use
@@ -167,7 +123,7 @@ void init_magics(PieceType pt, Bitboard table[], Magic magics[][2]) {
// the number of 1s of the mask. Hence we deduce the size of the shift to
// apply to the 64 or 32 bits word to get the index.
Magic& m = magics[s][pt - BISHOP];
m.mask = sliding_attack(pt, s, 0) & ~edges;
m.mask = Bitboards::sliding_attack(pt, s, 0) & ~edges;
#ifndef USE_PEXT
m.shift = (Is64Bit ? 64 : 32) - popcount(m.mask);
#endif
@@ -184,7 +140,7 @@ void init_magics(PieceType pt, Bitboard table[], Magic magics[][2]) {
#ifndef USE_PEXT
occupancy[size] = b;
#endif
reference[size] = sliding_attack(pt, s, b);
reference[size] = Bitboards::sliding_attack(pt, s, b);
if (HasPext)
m.attacks[pext(b, m.mask)] = reference[size];