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Code Issues Releases Wiki Activity

Rename yields_to_threat and prevents_threat

Browse source 
Follow Lucas suggestions and better name these
two functions.

No functional change.
This commit is contained in:
Marco Costalba 2012-12-26 12:15:55 +01:00
parent 894c43a1d6
commit db097921bc
1 changed files with 52 additions and 50 deletions
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102
src/search.cpp
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@ -99,8 +99,8 @@ namespace {
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
bool check_is_dangerous(Position& pos, Move move, Value futilityBase, Value beta);
bool yields_to_threat(const Position& pos, Move move, Move threat);
bool prevents_threat(const Position& pos, Move move, Move threat);
bool allows_move(const Position& pos, Move first, Move second);
bool prevents_move(const Position& pos, Move first, Move second);
string uci_pv(const Position& pos, int depth, Value alpha, Value beta);
struct Skill {
@ -683,7 +683,7 @@ namespace {
if ( depth < 5 * ONE_PLY
&& (ss-1)->reduction
&& threatMove != MOVE_NONE
&& yields_to_threat(pos, (ss-1)->currentMove, threatMove))
&& allows_move(pos, (ss-1)->currentMove, threatMove))
threatExtension = true;
}
}
@ -802,7 +802,7 @@ split_point_start: // At split points actual search starts from here
if (PvNode && dangerous)
ext = ONE_PLY;
else if (threatExtension && prevents_threat(pos, move, threatMove))
else if (threatExtension && prevents_move(pos, move, threatMove))
ext = ONE_PLY;
else if (givesCheck && pos.see_sign(move) >= 0)
@ -847,7 +847,7 @@ split_point_start: // At split points actual search starts from here
// Move count based pruning
if ( depth < 16 * ONE_PLY
&& moveCount >= FutilityMoveCounts[depth]
&& (!threatMove || !prevents_threat(pos, move, threatMove)))
&& (!threatMove || !prevents_move(pos, move, threatMove)))
{
if (SpNode)
sp->mutex.lock();
@ -1346,39 +1346,40 @@ split_point_start: // At split points actual search starts from here
}
// yields_to_threat() tests whether the move at previous ply yields to the so
// called threat move (the best move returned from a null search that fails
// low). Here 'yields to' means that the move somehow made the threat possible
// for instance if the moving piece is the same in both moves.
// allows_move() tests whether the move at previous ply (first) somehow makes a
// second move possible, for instance if the moving piece is the same in both
// moves. Normally the second move is the threat move (the best move returned
// from a null search that fails low).
bool yields_to_threat(const Position& pos, Move move, Move threat) {
bool allows_move(const Position& pos, Move first, Move second) {
assert(is_ok(move));
assert(is_ok(threat));
assert(color_of(pos.piece_on(from_sq(threat))) == ~pos.side_to_move());
assert(is_ok(first));
assert(is_ok(second));
assert(color_of(pos.piece_on(from_sq(second))) == ~pos.side_to_move());
assert(color_of(pos.piece_on(to_sq(first))) == ~pos.side_to_move());
Square mfrom = from_sq(move);
Square mto = to_sq(move);
Square tfrom = from_sq(threat);
Square tto = to_sq(threat);
Square m1from = from_sq(first);
Square m2from = from_sq(second);
Square m1to = to_sq(first);
Square m2to = to_sq(second);
// The piece is the same or threat's destination was vacated by the move
if (mto == tfrom || tto == mfrom)
// The piece is the same or second's destination was vacated by the first move
if (m1to == m2from || m2to == m1from)
return true;
// Threat moves through the vacated square
if (between_bb(tfrom, tto) & mfrom)
// Second one moves through the square vacated by first one
if (between_bb(m2from, m2to) & m1from)
return true;
// Threat's destination is defended by the move's piece
Bitboard matt = pos.attacks_from(pos.piece_on(mto), mto, pos.pieces() ^ tfrom);
if (matt & tto)
// Second's destination is defended by the first move's piece
Bitboard m1att = pos.attacks_from(pos.piece_on(m1to), m1to, pos.pieces() ^ m2from);
if (m1att & m2to)
return true;
// Threat gives a discovered check through the move's checking piece
if (matt & pos.king_square(pos.side_to_move()))
// Second move gives a discovered check through the first's checking piece
if (m1att & pos.king_square(pos.side_to_move()))
{
assert(between_bb(mto, pos.king_square(pos.side_to_move())) & tfrom);
assert(between_bb(m1to, pos.king_square(pos.side_to_move())) & m2from);
return true;
}
@ -1386,51 +1387,52 @@ split_point_start: // At split points actual search starts from here
}
// prevents_threat() tests whether a move is able to defend against the so
// called threat move (the best move returned from a null search that fails
// low). In this case will not be pruned.
// prevents_move() tests whether a move (first) is able to defend against an
// opponent's move (second). In this case will not be pruned. Normally the
// second move is the threat move (the best move returned from a null search
// that fails low).
bool prevents_threat(const Position& pos, Move move, Move threat) {
bool prevents_move(const Position& pos, Move first, Move second) {
assert(is_ok(move));
assert(is_ok(threat));
assert(!pos.is_capture_or_promotion(move));
assert(!pos.is_passed_pawn_push(move));
assert(is_ok(first));
assert(is_ok(second));
assert(!pos.is_capture_or_promotion(first));
assert(!pos.is_passed_pawn_push(first));
Square mfrom = from_sq(move);
Square mto = to_sq(move);
Square tfrom = from_sq(threat);
Square tto = to_sq(threat);
Square m1from = from_sq(first);
Square m2from = from_sq(second);
Square m1to = to_sq(first);
Square m2to = to_sq(second);
// Don't prune moves of the threatened piece
if (mfrom == tto)
if (m1from == m2to)
return true;
// If the threatened piece has value less than or equal to the value of the
// threat piece, don't prune moves which defend it.
if ( pos.is_capture(threat)
&& ( PieceValue[MG][pos.piece_on(tfrom)] >= PieceValue[MG][pos.piece_on(tto)]
|| type_of(pos.piece_on(tfrom)) == KING))
if ( pos.is_capture(second)
&& ( PieceValue[MG][pos.piece_on(m2from)] >= PieceValue[MG][pos.piece_on(m2to)]
|| type_of(pos.piece_on(m2from)) == KING))
{
// Update occupancy as if the piece and the threat are moving
Bitboard occ = pos.pieces() ^ mfrom ^ mto ^ tfrom;
Piece piece = pos.piece_on(mfrom);
Bitboard occ = pos.pieces() ^ m1from ^ m1to ^ m2from;
Piece piece = pos.piece_on(m1from);
// The moved piece attacks the square 'tto' ?
if (pos.attacks_from(piece, mto, occ) & tto)
if (pos.attacks_from(piece, m1to, occ) & m2to)
return true;
// Scan for possible X-ray attackers behind the moved piece
Bitboard xray = (attacks_bb< ROOK>(tto, occ) & pos.pieces(color_of(piece), QUEEN, ROOK))
| (attacks_bb<BISHOP>(tto, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP));
Bitboard xray = (attacks_bb< ROOK>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, ROOK))
| (attacks_bb<BISHOP>(m2to, occ) & pos.pieces(color_of(piece), QUEEN, BISHOP));
// Verify attackers are triggered by our move and not already existing
if (xray && (xray ^ (xray & pos.attacks_from<QUEEN>(tto))))
if (xray && (xray ^ (xray & pos.attacks_from<QUEEN>(m2to))))
return true;
}
// Don't prune safe moves which block the threat path
if ((between_bb(tfrom, tto) & mto) && pos.see_sign(move) >= 0)
if ((between_bb(m2from, m2to) & m1to) && pos.see_sign(first) >= 0)
return true;
return false;