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Speedup KPK bitbase of 25%

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Change the way the index is coded so that
now looping from 0 to IndexMax generates
the pawns from RANK_7 down to RANK2.

Becuase positions with pawns at RANK_7
are easily classified as wins/draws, this
small trick allows to reduce the number
of needed iterations from 30 down to 26!

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2013-02-13 12:26:08 +01:00
parent f2950ae206
commit 10d29add18
1 changed files with 4 additions and 4 deletions
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8
src/bitbase.cpp
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@ -39,9 +39,9 @@ namespace {
// bit 1- 6: black king square (from SQ_A1 to SQ_H8)
// bit 7-12: white king square (from SQ_A1 to SQ_H8)
// bit 13-14: white pawn file (from FILE_A to FILE_D)
// bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1)
// bit 15-17: white pawn 6 - rank (from 6 - RANK_7 to 6 - RANK_2)
unsigned index(Color stm, Square bksq, Square wksq, Square psq) {
return stm + (bksq << 1) + (wksq << 7) + (file_of(psq) << 13) + ((rank_of(psq) - 1) << 15);
return stm + (bksq << 1) + (wksq << 7) + (file_of(psq) << 13) + ((6 - rank_of(psq)) << 15);
}
enum Result {
@ -94,7 +94,7 @@ void Bitbases::init_kpk() {
for (idx = 0; idx < IndexMax; idx++)
db[idx].classify_leaf(idx);
// Iterate until all positions are classified (30 cycles needed)
// Iterate until all positions are classified (26 cycles needed)
while (repeat)
for (repeat = idx = 0; idx < IndexMax; idx++)
if (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN)
@ -114,7 +114,7 @@ namespace {
stm = Color(idx & 1);
bksq = Square((idx >> 1) & 0x3F);
wksq = Square((idx >> 7) & 0x3F);
psq = File((idx >> 13) & 3) | Rank((idx >> 15) + 1);
psq = File((idx >> 13) & 3) | Rank(6 - (idx >> 15));
// Check if two pieces are on the same square or if a king can be captured
if ( wksq == psq || wksq == bksq || bksq == psq