namespace {
enum MovegenPhase {
- PH_TT_MOVES, // Transposition table move and mate killer
- PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= 0
+ PH_TT_MOVE, // Transposition table move
+ PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= captureThreshold (captureThreshold <= 0)
+ PH_GOOD_PROBCUT, // Queen promotions and captures with SEE values > captureThreshold (captureThreshold >= 0)
PH_KILLERS, // Killer moves from the current ply
PH_NONCAPTURES, // Non-captures and underpromotions
- PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < 0
+ PH_BAD_CAPTURES, // Queen promotions and captures with SEE values < captureThreshold (captureThreshold <= 0)
PH_EVASIONS, // Check evasions
PH_QCAPTURES, // Captures in quiescence search
PH_QCHECKS, // Non-capture checks in quiescence search
};
CACHE_LINE_ALIGNMENT
- const uint8_t MainSearchTable[] = { PH_TT_MOVES, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP };
- const uint8_t EvasionTable[] = { PH_TT_MOVES, PH_EVASIONS, PH_STOP };
- const uint8_t QsearchWithChecksTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_QCHECKS, PH_STOP };
- const uint8_t QsearchWithoutChecksTable[] = { PH_TT_MOVES, PH_QCAPTURES, PH_STOP };
+ const uint8_t MainSearchTable[] = { PH_TT_MOVE, PH_GOOD_CAPTURES, PH_KILLERS, PH_NONCAPTURES, PH_BAD_CAPTURES, PH_STOP };
+ const uint8_t EvasionTable[] = { PH_TT_MOVE, PH_EVASIONS, PH_STOP };
+ const uint8_t QsearchWithChecksTable[] = { PH_TT_MOVE, PH_QCAPTURES, PH_QCHECKS, PH_STOP };
+ const uint8_t QsearchWithoutChecksTable[] = { PH_TT_MOVE, PH_QCAPTURES, PH_STOP };
+ const uint8_t ProbCutTable[] = { PH_TT_MOVE, PH_GOOD_PROBCUT, PH_STOP };
}
-bool MovePicker::isBadCapture() const { return phase == PH_BAD_CAPTURES; }
-
-/// Constructor for the MovePicker class. Apart from the position for which
-/// it is asked to pick legal moves, MovePicker also wants some information
+/// Constructors for the MovePicker class. As arguments we pass information
/// to help it to return the presumably good moves first, to decide which
/// moves to return (in the quiescence search, for instance, we only want to
/// search captures, promotions and some checks) and about how important good
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
SearchStack* ss, Value beta) : pos(p), H(h) {
- int searchTT = ttm;
- ttMoves[0].move = ttm;
- badCaptureThreshold = 0;
+ captureThreshold = 0;
badCaptures = moves + MAX_MOVES;
assert(d > DEPTH_ZERO);
if (p.in_check())
{
- ttMoves[1].move = killers[0].move = killers[1].move = MOVE_NONE;
+ killers[0].move = killers[1].move = MOVE_NONE;
phasePtr = EvasionTable;
}
else
{
- ttMoves[1].move = (ss->mateKiller == ttm) ? MOVE_NONE : ss->mateKiller;
- searchTT |= ttMoves[1].move;
killers[0].move = ss->killers[0];
killers[1].move = ss->killers[1];
// Consider sligtly negative captures as good if at low
// depth and far from beta.
if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * ONE_PLY)
- badCaptureThreshold = -PawnValueMidgame;
+ captureThreshold = -PawnValueMidgame;
phasePtr = MainSearchTable;
}
- phasePtr += int(!searchTT) - 1;
+ ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE);
+ phasePtr += int(ttMove == MOVE_NONE) - 1;
go_next_phase();
}
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h)
: pos(p), H(h) {
- int searchTT = ttm;
- ttMoves[0].move = ttm;
- ttMoves[1].move = MOVE_NONE;
assert(d <= DEPTH_ZERO);
// qsearch tree explosion due to a possible perpetual check or
// similar rare cases when TT table is full.
if (ttm != MOVE_NONE && !pos.move_is_capture(ttm) && !move_is_promotion(ttm))
- searchTT = ttMoves[0].move = MOVE_NONE;
+ ttm = MOVE_NONE;
}
- phasePtr += int(!searchTT) - 1;
+ ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE);
+ phasePtr += int(ttMove == MOVE_NONE) - 1;
+ go_next_phase();
+}
+
+MovePicker::MovePicker(const Position& p, Move ttm, const History& h, int parentCapture)
+ : pos(p), H(h) {
+
+ assert (!pos.in_check());
+
+ // In ProbCut we consider only captures better than parent's move
+ captureThreshold = parentCapture;
+ phasePtr = ProbCutTable;
+
+ if ( ttm != MOVE_NONE
+ && (!pos.move_is_capture(ttm) || pos.see(ttm) <= captureThreshold))
+ ttm = MOVE_NONE;
+
+ ttMove = (ttm && pos.move_is_pl(ttm) ? ttm : MOVE_NONE);
+ phasePtr += int(ttMove == MOVE_NONE) - 1;
go_next_phase();
}
phase = *(++phasePtr);
switch (phase) {
- case PH_TT_MOVES:
- curMove = ttMoves;
- lastMove = curMove + 2;
+ case PH_TT_MOVE:
+ lastMove = curMove + 1;
return;
case PH_GOOD_CAPTURES:
+ case PH_GOOD_PROBCUT:
lastMove = generate<MV_CAPTURE>(pos, moves);
score_captures();
return;
}
/// MovePicker::get_next_move() is the most important method of the MovePicker
-/// class. It returns a new legal move every time it is called, until there
+/// class. It returns a new pseudo legal move every time it is called, until there
/// are no more moves left. It picks the move with the biggest score from a list
/// of generated moves taking care not to return the tt move if has already been
/// searched previously. Note that this function is not thread safe so should be
switch (phase) {
- case PH_TT_MOVES:
- move = (curMove++)->move;
- if ( move != MOVE_NONE
- && pos.move_is_pl(move))
- return move;
+ case PH_TT_MOVE:
+ curMove++;
+ return ttMove;
break;
case PH_GOOD_CAPTURES:
move = pick_best(curMove++, lastMove).move;
- if ( move != ttMoves[0].move
- && move != ttMoves[1].move)
+ if (move != ttMove)
{
+ assert(captureThreshold <= 0); // Otherwise we must use see instead of see_sign
+
// Check for a non negative SEE now
int seeValue = pos.see_sign(move);
- if (seeValue >= badCaptureThreshold)
+ if (seeValue >= captureThreshold)
return move;
// Losing capture, move it to the tail of the array, note
- // that move has now been already checked for legality.
+ // that move has now been already checked for pseudo legality.
(--badCaptures)->move = move;
badCaptures->score = seeValue;
}
break;
+ case PH_GOOD_PROBCUT:
+ move = pick_best(curMove++, lastMove).move;
+ if ( move != ttMove
+ && pos.see(move) > captureThreshold)
+ return move;
+ break;
+
case PH_KILLERS:
move = (curMove++)->move;
if ( move != MOVE_NONE
&& pos.move_is_pl(move)
- && move != ttMoves[0].move
- && move != ttMoves[1].move
+ && move != ttMove
&& !pos.move_is_capture(move))
return move;
break;
insertion_sort<MoveStack>(lastGoodNonCapture, lastMove);
move = (curMove++)->move;
- if ( move != ttMoves[0].move
- && move != ttMoves[1].move
+ if ( move != ttMove
&& move != killers[0].move
&& move != killers[1].move)
return move;
case PH_EVASIONS:
case PH_QCAPTURES:
move = pick_best(curMove++, lastMove).move;
- if (move != ttMoves[0].move)
+ if (move != ttMove)
return move;
break;
case PH_QCHECKS:
move = (curMove++)->move;
- if ( move != ttMoves[0].move)
+ if (move != ttMove)
return move;
break;
projects / stockfish / blobdiff