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Add a known draw case in kpk bitbase generation

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Early classify as known draws the positions
where white king is trapped on the rook file.

Suggested by Dan Honeycutt.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2012-05-19 08:38:23 +01:00
parent f86182e791
commit 0ecc920a09
1 changed files with 8 additions and 1 deletions
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9
src/bitbase.cpp
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@ -156,7 +156,7 @@ namespace {
&& rank_of(psq) < RANK_7)
return DRAW;
// Case 4: White king in front of pawn and black has opposition
// Case 4: White king in front of pawn and black has opposition
if ( stm == WHITE
&& wksq == psq + DELTA_N
&& bksq == wksq + DELTA_N + DELTA_N
@ -168,6 +168,13 @@ namespace {
&& file_of(psq) == FILE_A)
return DRAW;
// Case 6: White king trapped on the rook file
if ( file_of(wksq) == FILE_A
&& file_of(psq) == FILE_A
&& rank_of(wksq) > rank_of(psq)
&& bksq == wksq + 2)
return DRAW;
return UNKNOWN;
}