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When generating checks add possibly under-promotions

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In qsearch at depth 0 we generate only captures and checks.
Queen promotion moves are generated among the captures, but
under-promotion moves (both captures and non-captures) are
never generated even if they could give a discovery check.

This patch fixes this limitation extending generate_pawn_noncaptures()
to generate also check moves when required.

Apart for adding the (rare) case of an under-promotion that gives
discovery check, the patch is also a good cleanup because removes
generate_pawn_checks() altoghter.

This patch does the code clean-up but not enables the functional
change so to allow an easier debug.

No functional change and no performance change (actually a very
very small speed increase).

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-09-21 10:00:33 +01:00
parent aaffcf973e
commit aed542d74c
1 changed files with 29 additions and 71 deletions
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100
src/movegen.cpp
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@ -66,11 +66,8 @@ namespace {
template<Color Us, SquareDelta Diagonal>
MoveStack* generate_pawn_captures_diagonal(MoveStack* mlist, Bitboard pawns, Bitboard enemyPieces, bool promotion);
template<Color Us>
MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist);
template<Color Us>
MoveStack* generate_pawn_checks(const Position&, Bitboard, Square, MoveStack*);
template<Color Us, bool Checks>
MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist, Bitboard dc = EmptyBoardBB, Square ksq = SQ_NONE);
template<Color Us, SquareDelta Direction>
inline Bitboard move_pawns(Bitboard p) {
@ -92,8 +89,8 @@ namespace {
template<>
inline MoveStack* generate_piece_checks<PAWN>(const Position& p, MoveStack* m, Color us, Bitboard dc, Square ksq) {
return (us == WHITE ? generate_pawn_checks<WHITE>(p, dc, ksq, m)
: generate_pawn_checks<BLACK>(p, dc, ksq, m));
return (us == WHITE ? generate_pawn_noncaptures<WHITE, true>(p, m, dc, ksq)
: generate_pawn_noncaptures<BLACK, true>(p, m, dc, ksq));
}
// Template generate_piece_moves() with specializations and overloads
@ -112,8 +109,8 @@ namespace {
return (us == WHITE ? generate_pawn_captures<WHITE>(p, m)
: generate_pawn_captures<BLACK>(p, m));
else
return (us == WHITE ? generate_pawn_noncaptures<WHITE>(p, m)
: generate_pawn_noncaptures<BLACK>(p, m));
return (us == WHITE ? generate_pawn_noncaptures<WHITE, false>(p, m)
: generate_pawn_noncaptures<BLACK, false>(p, m));
}
template<PieceType>
@ -712,10 +709,11 @@ namespace {
return mlist;
}
template<Color Us>
MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist) {
template<Color Us, bool GenerateChecks>
MoveStack* generate_pawn_noncaptures(const Position& pos, MoveStack* mlist, Bitboard dc, Square ksq) {
// Calculate our parametrized parameters at compile time
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
const Bitboard TRank7BB = (Us == WHITE ? Rank7BB : Rank2BB);
const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
@ -723,17 +721,20 @@ namespace {
const SquareDelta TDELTA_NW = (Us == WHITE ? DELTA_NW : DELTA_SW);
const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
Bitboard b1, b2;
Bitboard b1, b2, dcPawns1, dcPawns2;
Square to;
Bitboard pawns = pos.pieces(PAWN, Us);
Bitboard emptySquares = pos.empty_squares();
if (pawns & TRank7BB) // There is some promotion candidate ?
{
Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
// When generating checks consider under-promotion moves (both captures
// and non captures) only if can give a discovery check.
Bitboard pp = GenerateChecks ? pawns & dc & EmptyBoardBB: pawns;
Bitboard enemyPieces = pos.pieces_of_color(opposite_color(Us));
// Underpromotion captures in the a1-h8 (a8-h1 for black) direction
b1 = move_pawns<Us, DELTA_NE>(pawns) & ~FileABB & enemyPieces & TRank8BB;
b1 = move_pawns<Us, DELTA_NE>(pp) & ~FileABB & enemyPieces & TRank8BB;
while (b1)
{
to = pop_1st_bit(&b1);
@ -743,7 +744,7 @@ namespace {
}
// Underpromotion captures in the h1-a8 (h8-a1 for black) direction
b1 = move_pawns<Us, DELTA_NW>(pawns) & ~FileHBB & enemyPieces & TRank8BB;
b1 = move_pawns<Us, DELTA_NW>(pp) & ~FileHBB & enemyPieces & TRank8BB;
while (b1)
{
to = pop_1st_bit(&b1);
@ -753,7 +754,7 @@ namespace {
}
// Underpromotion pawn pushes
b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares & TRank8BB;
b1 = move_pawns<Us, DELTA_N>(pp) & emptySquares & TRank8BB;
while (b1)
{
to = pop_1st_bit(&b1);
@ -763,68 +764,25 @@ namespace {
}
}
// Single pawn pushes
b2 = b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares & ~TRank8BB;
SERIALIZE_MOVES_D(b2, -TDELTA_N);
// Double pawn pushes
b2 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
return mlist;
}
template<Color Us>
MoveStack* generate_pawn_checks(const Position& pos, Bitboard dc, Square ksq, MoveStack* mlist)
{
// Calculate our parametrized parameters at compile time
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Bitboard TRank8BB = (Us == WHITE ? Rank8BB : Rank1BB);
const Bitboard TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
const SquareDelta TDELTA_N = (Us == WHITE ? DELTA_N : DELTA_S);
const SquareDelta TDELTA_S = (Us == WHITE ? DELTA_S : DELTA_N);
Square to;
Bitboard b1, b2, b3;
Bitboard pawns = pos.pieces(PAWN, Us);
if (dc & pawns)
dcPawns1 = dcPawns2 = EmptyBoardBB;
if (GenerateChecks && (dc & pawns))
{
Bitboard empty = pos.empty_squares();
// Pawn moves which gives discovered check. This is possible only if the
// pawn is not on the same file as the enemy king, because we don't
// generate captures.
b1 = pawns & ~file_bb(ksq);
// Discovered checks, single pawn pushes, no promotions
b2 = b3 = move_pawns<Us, DELTA_N>(b1 & dc) & empty & ~TRank8BB;
SERIALIZE_MOVES_D(b3, -TDELTA_N);
// Discovered checks, double pawn pushes
b3 = move_pawns<Us, DELTA_N>(b2 & TRank3BB) & empty;
SERIALIZE_MOVES_D(b3, -TDELTA_N -TDELTA_N);
dcPawns1 = move_pawns<Us, DELTA_N>(pawns & dc & ~file_bb(ksq)) & emptySquares & ~TRank8BB;
dcPawns2 = move_pawns<Us, DELTA_N>(dcPawns1 & TRank3BB) & emptySquares;
}
// Direct checks. These are possible only for pawns on neighboring files
// and in the two ranks that, after the push, are in front of the enemy king.
b1 = pawns & neighboring_files_bb(ksq) & ~dc;
// Single pawn pushes
b1 = move_pawns<Us, DELTA_N>(pawns) & emptySquares & ~TRank8BB;
b2 = GenerateChecks ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns1 : b1;
SERIALIZE_MOVES_D(b2, -TDELTA_N);
// We can get false positives if (ksq + x) is not in [0,63] range but
// is not a problem, they will be filtered out later.
b2 = b1 & (rank_bb(ksq + 2 * TDELTA_S) | rank_bb(ksq + 3 * TDELTA_S));
if (!b2)
return mlist;
// Direct checks, single pawn pushes
Bitboard empty = pos.empty_squares();
b2 = move_pawns<Us, DELTA_N>(b1) & empty;
b3 = b2 & pos.attacks_from<PAWN>(ksq, Them);
SERIALIZE_MOVES_D(b3, -TDELTA_N);
// Direct checks, double pawn pushes
b3 = move_pawns<Us, DELTA_N>(b2 & TRank3BB) & empty & pos.attacks_from<PAWN>(ksq, Them);
SERIALIZE_MOVES_D(b3, -TDELTA_N -TDELTA_N);
// Double pawn pushes
b1 = move_pawns<Us, DELTA_N>(b1 & TRank3BB) & emptySquares;
b2 = GenerateChecks ? (b1 & pos.attacks_from<PAWN>(ksq, Them)) | dcPawns2 : b1;
SERIALIZE_MOVES_D(b2, -TDELTA_N -TDELTA_N);
return mlist;
}