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Try bad captures before non-captures

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Consider sligtly negative captures as good if at low
depth and far from beta.

After 999 games at 1+0
Mod vs Orig +169 =694 -136  +11 ELO

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2010-02-27 17:09:07 +01:00
parent 68eb7e77f1
commit 14dbeb22dd
3 changed files with 13 additions and 6 deletions
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13
src/movepick.cpp
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@@ -71,10 +71,11 @@ namespace {
/// move ordering is at the current node.
MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
const History& h, SearchStack* ss) : pos(p), H(h) {
const History& h, SearchStack* ss, Value beta) : pos(p), H(h) {
int searchTT = ttm;
ttMoves[0].move = ttm;
lastBadCapture = badCaptures;
badCaptureThreshold = 0;
pinned = p.pinned_pieces(pos.side_to_move());
@@ -90,8 +91,14 @@ MovePicker::MovePicker(const Position& p, Move ttm, Depth d,
if (p.is_check())
phasePtr = EvasionsPhaseTable;
else if (d > Depth(0))
{
// Consider sligtly negative captures as good if at low
// depth and far from beta.
if (ss && ss->eval < beta - PawnValueMidgame && d < 3 * OnePly)
badCaptureThreshold = -PawnValueMidgame;
phasePtr = MainSearchPhaseTable;
else if (d == Depth(0))
} else if (d == Depth(0))
phasePtr = QsearchWithChecksPhaseTable;
else
{
@@ -290,7 +297,7 @@ Move MovePicker::get_next_move() {
{
// Check for a non negative SEE now
int seeValue = pos.see_sign(move);
if (seeValue >= 0)
if (seeValue >= badCaptureThreshold)
return move;
// Losing capture, move it to the badCaptures[] array, note