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Clarify the mapping of files to queenside

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Author: @nickpelling

We replace in the code the obscure expressions mapping files ABCDEFGH to ABCDDCBA
by an explicite call to an auxiliary function :

  old:   f = min(f, ~f)
  new:   f = map_to_queenside(f)

We used the Golbolt web site (https://godbolt.org) to find the optimal code
for the auxiliary function.

STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 30292 W: 6756 L: 6651 D: 16885
http://tests.stockfishchess.org/tests/view/5d8676720ebc5971531d6aa1

No functional change
This commit is contained in:
Stéphane Nicolet 2019-09-23 08:52:27 +02:00
parent 770c8d92f3
commit 7756344d5d
4 changed files with 7 additions and 3 deletions
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2
src/evaluate.cpp
View file

@ -662,7 +662,7 @@ namespace {
|| (pos.pieces(PAWN) & (s + Up)))
bonus = bonus / 2;
score += bonus - PassedFile * std::min(f, ~f);
score += bonus - PassedFile * map_to_queenside(f);
}
if (T)

2
src/pawns.cpp
View file

@ -198,7 +198,7 @@ Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
b = theirPawns & file_bb(f);
int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
int d = std::min(f, ~f);
int d = map_to_queenside(f);
bonus += make_score(ShelterStrength[d][ourRank], 0);
if (ourRank && (ourRank == theirRank - 1))

2
src/psqt.cpp
View file

@ -119,7 +119,7 @@ void init() {
for (Square s = SQ_A1; s <= SQ_H8; ++s)
{
File f = std::min(file_of(s), ~file_of(s));
File f = map_to_queenside(file_of(s));
psq[ pc][ s] = score + (type_of(pc) == PAWN ? PBonus[rank_of(s)][file_of(s)]
: Bonus[pc][rank_of(s)][f]);
psq[~pc][~s] = -psq[pc][s];

4
src/types.h
View file

@ -366,6 +366,10 @@ constexpr Piece operator~(Piece pc) {
return Piece(pc ^ 8); // Swap color of piece B_KNIGHT -> W_KNIGHT
}
inline File map_to_queenside(File f) {
return std::min(f, File(FILE_H - f)); // Map files ABCDEFGH to files ABCDDCBA
}
constexpr CastlingRights operator&(Color c, CastlingRights cr) {
return CastlingRights((c == WHITE ? WHITE_CASTLING : BLACK_CASTLING) & cr);
}