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Retire pawn storm evaluation

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More then 100 lines of almost useless evaluations. Prefer
code semplification to a very small and dubious advantage.

After 7457 games on russian cluster:
Mod - Orig: 1285 - 1334 - 4838  ELO -2 (+- 3.2)

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Joona Kiiski
2010-09-06 10:53:10 +03:00
committed by Marco Costalba
parent 5b5b496a6d
commit fa2478a81f
3 changed files with 7 additions and 112 deletions
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81
src/pawns.cpp
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@@ -70,36 +70,6 @@ namespace {
S(34,68), S(83,166), S(0, 0), S( 0, 0)
};
// Pawn storm tables for positions with opposite castling
const int QStormTable[64] = {
0, 0, 0, 0, 0, 0, 0, 0,
-22,-22,-22,-14,-6, 0, 0, 0,
-6,-10,-10,-10,-6, 0, 0, 0,
4, 12, 16, 12, 4, 0, 0, 0,
16, 23, 23, 16, 0, 0, 0, 0,
23, 31, 31, 23, 0, 0, 0, 0,
23, 31, 31, 23, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0
};
const int KStormTable[64] = {
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0,-10,-19,-28,-33,-33,
0, 0, 0,-10,-15,-19,-24,-24,
0, 0, 0, 0, 1, 1, 1, 1,
0, 0, 0, 0, 1, 10, 19, 19,
0, 0, 0, 0, 1, 19, 31, 27,
0, 0, 0, 0, 0, 22, 31, 22,
0, 0, 0, 0, 0, 0, 0, 0
};
// Pawn storm open file bonuses by file
const int16_t QStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 };
const int16_t KStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 };
// Pawn storm lever bonuses by file
const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 };
#undef S
}
@@ -175,35 +145,22 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
Square s;
File f;
Rank r;
int bonus;
bool passed, isolated, doubled, opposed, chain, backward, candidate;
Score value = SCORE_ZERO;
const Square* ptr = pos.piece_list_begin(Us, PAWN);
// Initialize pawn storm scores by giving bonuses for open files
// Initialize halfOpenFiles[]
for (f = FILE_A; f <= FILE_H; f++)
if (!(ourPawns & file_bb(f)))
{
pi->ksStormValue[Us] += KStormOpenFileBonus[f];
pi->qsStormValue[Us] += QStormOpenFileBonus[f];
pi->halfOpenFiles[Us] |= (1 << f);
}
// Loop through all pawns of the current color and score each pawn
while ((s = *ptr++) != SQ_NONE)
{
f = square_file(s);
r = square_rank(s);
assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
// Calculate kingside and queenside pawn storm scores for both colors to be
// used when evaluating middle game positions with opposite side castling.
bonus = (f >= FILE_F ? evaluate_pawn_storm<Us, KingSide>(s, r, f, theirPawns) : 0);
pi->ksStormValue[Us] += KStormTable[relative_square(Us, s)] + bonus;
bonus = (f <= FILE_C ? evaluate_pawn_storm<Us, QueenSide>(s, r, f, theirPawns) : 0);
pi->qsStormValue[Us] += QStormTable[relative_square(Us, s)] + bonus;
f = square_file(s);
r = square_rank(s);
// Our rank plus previous one. Used for chain detection.
b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
@@ -288,35 +245,3 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
return value;
}
/// PawnInfoTable::evaluate_pawn_storm() evaluates each pawn which seems
/// to have good chances of creating an open file by exchanging itself
/// against an enemy pawn on an adjacent file.
template<Color Us, PawnInfoTable::SideType Side>
int PawnInfoTable::evaluate_pawn_storm(Square s, Rank r, File f, Bitboard theirPawns) const {
const Bitboard StormFilesBB = (Side == KingSide ? FileFBB | FileGBB | FileHBB
: FileABB | FileBBB | FileCBB);
const int K = (Side == KingSide ? 2 : 4);
const File RookFile = (Side == KingSide ? FILE_H : FILE_A);
Bitboard b = attack_span_mask(Us, s) & theirPawns & StormFilesBB;
int bonus = 0;
while (b)
{
// Give a bonus according to the distance of the nearest enemy pawn
Square s2 = pop_1st_bit(&b);
Rank r2 = square_rank(s2);
int v = StormLeverBonus[f] - K * rank_distance(r, r2);
// If enemy pawn has no pawn beside itself is particularly vulnerable.
// Big bonus, especially against a weakness on the rook file
if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
v *= (square_file(s2) == RookFile ? 4 : 2);
bonus += v;
}
return bonus;
}