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Clarify the mapping of files to queenside

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This patch replaces the obscure expressions mapping files ABCDEFGH to ABCDDCBA
by explicite calls 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 check that the current
code for the auxiliary function is optimal.

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

Achieved with a bit of help from Sopel97, snicolet and vondele, thanks everyone!
Closes https://github.com/official-stockfish/Stockfish/pull/2325

No functional change
This commit is contained in:
nickpelling 2019-09-21 08:59:32 +01:00 • committed by Stéphane Nicolet
parent defa1ccaa9
commit d232a4ae68
5 changed files with 9 additions and 7 deletions
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1
AUTHORS
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@ -99,6 +99,7 @@ Miroslav Fontán (Hexik)
Moez Jellouli (MJZ1977) Moez Jellouli (MJZ1977)
Mohammed Li (tthsqe12) Mohammed Li (tthsqe12)
Nathan Rugg (nmrugg) Nathan Rugg (nmrugg)
Nick Pelling (nickpelling)
Nicklas Persson (NicklasPersson) Nicklas Persson (NicklasPersson)
Niklas Fiekas (niklasf) Niklas Fiekas (niklasf)
Ondrej Mosnáček (WOnder93) Ondrej Mosnáček (WOnder93)

2
src/evaluate.cpp
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@ -662,7 +662,7 @@ namespace {
|| (pos.pieces(PAWN) & (s + Up))) || (pos.pieces(PAWN) & (s + Up)))
bonus = bonus / 2; bonus = bonus / 2;
score += bonus - PassedFile * std::min(f, ~f); score += bonus - PassedFile * map_to_queenside(f);
} }
if (T) 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); b = theirPawns & file_bb(f);
int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
int d = std::min(f, ~f); File d = map_to_queenside(f);
bonus += make_score(ShelterStrength[d][ourRank], 0); bonus += make_score(ShelterStrength[d][ourRank], 0);
if (ourRank && (ourRank == theirRank - 1)) if (ourRank && (ourRank == theirRank - 1))

2
src/psqt.cpp
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@ -119,7 +119,7 @@ void init() {
for (Square s = SQ_A1; s <= SQ_H8; ++s) 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)] psq[ pc][ s] = score + (type_of(pc) == PAWN ? PBonus[rank_of(s)][file_of(s)]
: Bonus[pc][rank_of(s)][f]); : Bonus[pc][rank_of(s)][f]);
psq[~pc][~s] = -psq[pc][s]; psq[~pc][~s] = -psq[pc][s];

9
src/types.h
View file

@ -43,6 +43,7 @@
#include <climits> #include <climits>
#include <cstdint> #include <cstdint>
#include <cstdlib> #include <cstdlib>
#include <algorithm>
#if defined(_MSC_VER) #if defined(_MSC_VER)
// Disable some silly and noisy warning from MSVC compiler // Disable some silly and noisy warning from MSVC compiler
@ -358,14 +359,14 @@ constexpr Square operator~(Square s) {
return Square(s ^ SQ_A8); // Vertical flip SQ_A1 -> SQ_A8 return Square(s ^ SQ_A8); // Vertical flip SQ_A1 -> SQ_A8
} }
constexpr File operator~(File f) {
return File(f ^ FILE_H); // Horizontal flip FILE_A -> FILE_H
}
constexpr Piece operator~(Piece pc) { constexpr Piece operator~(Piece pc) {
return Piece(pc ^ 8); // Swap color of piece B_KNIGHT -> W_KNIGHT 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) { constexpr CastlingRights operator&(Color c, CastlingRights cr) {
return CastlingRights((c == WHITE ? WHITE_CASTLING : BLACK_CASTLING) & cr); return CastlingRights((c == WHITE ? WHITE_CASTLING : BLACK_CASTLING) & cr);
} }