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Retire PieceOffset[] in book.cpp

Browse source 
And calculate piece offset on the fly. Also
improve comments.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2012-05-27 13:43:15 +01:00
parent 61a054b170
commit 6828325881
1 changed files with 5 additions and 6 deletions
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11
src/book.cpp
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@ -306,11 +306,6 @@ namespace {
const Key* ZobEnPassant = PolyGlotRandoms + 772;
const Key* ZobTurn = PolyGlotRandoms + 780;
// PieceOffset is calculated as 64 * (PolyPiece ^ 1) where PolyPiece
// is: BP = 0, WP = 1, BN = 2, WN = 3 ... BK = 10, WK = 11
const int PieceOffset[] = { 0, 64, 192, 320, 448, 576, 704, 0,
0, 0, 128, 256, 384, 512, 640 };
// book_key() returns the PolyGlot hash key of the given position
uint64_t book_key(const Position& pos) {
@ -319,8 +314,12 @@ namespace {
while (b)
{
// Piece offset is at 64 * polyPiece where polyPiece is defined as:
// BP = 0, WP = 1, BN = 2, WN = 3, ... BK = 10, WK = 11
Square s = pop_1st_bit(&b);
key ^= ZobPiece[PieceOffset[pos.piece_on(s)] + s];
Piece p = pos.piece_on(s);
int polyPiece = 2 * (type_of(p) - 1) + (color_of(p) == WHITE);
key ^= ZobPiece[64 * polyPiece + s];
}
b = pos.can_castle(ALL_CASTLES);