Use int8_t instead of int for SquareDistance[]

This patch saves (4-1) * 64 * 64 = 12KiB of cache.

STC
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 176120 W: 38944 L: 38087 D: 99089
http://tests.stockfishchess.org/tests/view/5c4c9f840ebc593af5d4a7ce

LTC
As a pure speed up, I've been informed it should not require LTC.

No functional change

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 77f49ef675c506ce175a7cc4658661ff2530b65d..105d201f1c17de3ca2cfc9a1cad5a2d9aab4efd7 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -24,7 +24,7 @@
 #include "misc.h"
 
 uint8_t PopCnt16[1 << 16];
-int SquareDistance[SQUARE_NB][SQUARE_NB];
+int8_t SquareDistance[SQUARE_NB][SQUARE_NB];
 
 Bitboard SquareBB[SQUARE_NB];
 Bitboard FileBB[FILE_NB];

diff --git a/src/bitboard.h b/src/bitboard.h
index e1c31dd7c5fd1525dc61712de06fa55cf760ac7b..b64c92e1a4c54107ef2088ddf43d69c9cafc6871 100644 (file)
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -60,7 +60,7 @@ constexpr Bitboard Rank6BB = Rank1BB << (8 * 5);
 constexpr Bitboard Rank7BB = Rank1BB << (8 * 6);
 constexpr Bitboard Rank8BB = Rank1BB << (8 * 7);
 
-extern int SquareDistance[SQUARE_NB][SQUARE_NB];
+extern int8_t SquareDistance[SQUARE_NB][SQUARE_NB];
 
 extern Bitboard SquareBB[SQUARE_NB];
 extern Bitboard FileBB[FILE_NB];