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New extended probcut implementation

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Here the idea is to test probcut not only after bad
captures, but after any bad move, i.e. any move that
leaves the opponent with a good capture.

Ported by a patch from Onno, the difference from
original version is that we have moved probcut after
null search.

After 7917 games 4 threads 20"+0.1
Mod vs Orig: 1261 - 1095 - 5561 ELO +7 (+- 4.2) LOS 96%

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2011-05-21 17:17:11 +01:00
parent 462a39ec49
commit fca0a2dd88
4 changed files with 87 additions and 42 deletions
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44
src/movepick.cpp
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@@ -29,10 +29,11 @@ namespace {
enum MovegenPhase {
PH_TT_MOVE, // Transposition table move
PH_GOOD_CAPTURES, // Queen promotions and captures with SEE values >= 0
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
@@ -44,11 +45,10 @@ namespace {
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. As arguments we pass 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
@@ -56,7 +56,7 @@ bool MovePicker::isBadCapture() const { return phase == PH_BAD_CAPTURES; }
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
SearchStack* ss, Value beta) : pos(p), H(h) {
badCaptureThreshold = 0;
captureThreshold = 0;
badCaptures = moves + MAX_MOVES;
assert(d > DEPTH_ZERO);
@@ -74,7 +74,7 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h,
// 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;
}
@@ -109,6 +109,24 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const History& h)
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();
}
/// MovePicker::go_next_phase() generates, scores and sorts the next bunch
/// of moves when there are no more moves to try for the current phase.
@@ -124,6 +142,7 @@ void MovePicker::go_next_phase() {
return;
case PH_GOOD_CAPTURES:
case PH_GOOD_PROBCUT:
lastMove = generate<MV_CAPTURE>(pos, moves);
score_captures();
return;
@@ -270,9 +289,11 @@ Move MovePicker::get_next_move() {
move = pick_best(curMove++, lastMove).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
@@ -282,6 +303,13 @@ Move MovePicker::get_next_move() {
}
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