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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)
Mohammed Li (tthsqe12)
Nathan Rugg (nmrugg)
Nick Pelling (nickpelling)
Nicklas Persson (NicklasPersson)
Niklas Fiekas (niklasf)
Ondrej Mosnáček (WOnder93)

2
src/evaluate.cpp
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@@ -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
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@@ -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);
File d = map_to_queenside(f);
bonus += make_score(ShelterStrength[d][ourRank], 0);
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)
{
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];

9
src/types.h
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@@ -43,6 +43,7 @@
#include <climits>
#include <cstdint>
#include <cstdlib>
#include <algorithm>
#if defined(_MSC_VER)
// 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
}
constexpr File operator~(File f) {
return File(f ^ FILE_H); // Horizontal flip FILE_A -> FILE_H
}
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);
}