From 3300517ecb75df265489d2a9841e4fce2414fd09 Mon Sep 17 00:00:00 2001
From: protonspring <mike@whiteley.org>
Date: Mon, 14 Jan 2019 22:53:43 -0700
Subject: [PATCH] Remove AdjacentFiles

This is a non-functional simplification that removes the AdjacentFiles array.
This array is simple enough to calculate that the pre-calculated array provides
no benefit. Reduces the memory footprint.

STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 74839 W: 16390 L: 16373 D: 42076
http://tests.stockfishchess.org/tests/view/5c3d75920ebc596a450cfb67

No functionnal change
---
 src/bitboard.cpp | 6 +-----
 src/bitboard.h   | 3 +--
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 8079b783..77f49ef6 100644
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -29,7 +29,6 @@ int SquareDistance[SQUARE_NB][SQUARE_NB];
 Bitboard SquareBB[SQUARE_NB];
 Bitboard FileBB[FILE_NB];
 Bitboard RankBB[RANK_NB];
-Bitboard AdjacentFilesBB[FILE_NB];
 Bitboard ForwardRanksBB[COLOR_NB][RANK_NB];
 Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
 Bitboard LineBB[SQUARE_NB][SQUARE_NB];
@@ -97,9 +96,6 @@ void Bitboards::init() {
   for (Rank r = RANK_1; r <= RANK_8; ++r)
       RankBB[r] = r > RANK_1 ? RankBB[r - 1] << 8 : Rank1BB;
 
-  for (File f = FILE_A; f <= FILE_H; ++f)
-      AdjacentFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
-
   for (Rank r = RANK_1; r < RANK_8; ++r)
       ForwardRanksBB[WHITE][r] = ~(ForwardRanksBB[BLACK][r + 1] = ForwardRanksBB[BLACK][r] | RankBB[r]);
 
@@ -107,7 +103,7 @@ void Bitboards::init() {
       for (Square s = SQ_A1; s <= SQ_H8; ++s)
       {
           ForwardFileBB [c][s] = ForwardRanksBB[c][rank_of(s)] & FileBB[file_of(s)];
-          PawnAttackSpan[c][s] = ForwardRanksBB[c][rank_of(s)] & AdjacentFilesBB[file_of(s)];
+          PawnAttackSpan[c][s] = ForwardRanksBB[c][rank_of(s)] & adjacent_files_bb(file_of(s));
           PassedPawnMask[c][s] = ForwardFileBB [c][s] | PawnAttackSpan[c][s];
       }
 
diff --git a/src/bitboard.h b/src/bitboard.h
index f8440a23..e1c31dd7 100644
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -65,7 +65,6 @@ extern int SquareDistance[SQUARE_NB][SQUARE_NB];
 extern Bitboard SquareBB[SQUARE_NB];
 extern Bitboard FileBB[FILE_NB];
 extern Bitboard RankBB[RANK_NB];
-extern Bitboard AdjacentFilesBB[FILE_NB];
 extern Bitboard ForwardRanksBB[COLOR_NB][RANK_NB];
 extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
 extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
@@ -195,7 +194,7 @@ constexpr Bitboard double_pawn_attacks_bb(Bitboard b) {
 /// adjacent files of the given one.
 
 inline Bitboard adjacent_files_bb(File f) {
-  return AdjacentFilesBB[f];
+  return shift<EAST>(FileBB[f]) | shift<WEST>(FileBB[f]);
 }
 
 
-- 
2.39.2