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Better clarify why recent generate_pawn_checks() works

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We can have false positives, but these are filtered out
anyhow by following conditions so they are harmless.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-06-12 12:05:48 +02:00
parent b5685fc564
commit 8bec65029d
1 changed files with 6 additions and 4 deletions
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10
src/movegen.cpp
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@ -132,7 +132,7 @@ namespace {
/// generate_captures generates() all pseudo-legal captures and queen /// generate_captures generates() all pseudo-legal captures and queen
/// promotions. The return value is the number of moves generated. /// promotions. The return value is the number of moves generated.
int generate_captures(const Position& pos, MoveStack* mlist) { int generate_captures(const Position& pos, MoveStack* mlist) {
@ -791,9 +791,11 @@ namespace {
// Direct checks. These are possible only for pawns on neighboring files // Direct checks. These are possible only for pawns on neighboring files
// and in the two ranks that, after the push, are in front of the enemy king. // and in the two ranks that, after the push, are in front of the enemy king.
b1 = pawns & neighboring_files_bb(ksq) & ~dc; b1 = pawns & neighboring_files_bb(ksq) & ~dc;
b2 = rank_bb(ksq + 2 * TDELTA_S) | rank_bb(ksq + 3 * TDELTA_S);
b1 &= b2; // We can get false positives if (ksq + x) is not in [0,63] range but
if (!b1) // is not a problem, they will be filtered out later.
b2 = b1 & (rank_bb(ksq + 2 * TDELTA_S) | rank_bb(ksq + 3 * TDELTA_S));
if (!b2)
return mlist; return mlist;
// Direct checks, single pawn pushes // Direct checks, single pawn pushes