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Big King Safety tuning

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ShelterWeakness and Stormdanger array are now indexed additionally by
file pair (a/h,b/g,c/f,d/e). The special case of king blocking a pawn
is incorporated in the StormDanger array.  Finally the 93 parameters
are tuned by SPSA on LTC.

STC
ELO: 3.46 +-2.2 (95%) LOS: 99.9%
Total: 40000 W: 8275 L: 7877 D: 23848

LTC
LLR: 2.96 (-2.94,2.94) [0.00,6.00]
Total: 10311 W: 1876 L: 1721 D: 6714

Bench: 9498821

Resolves #163
This commit is contained in:
Stefan Geschwentner 2014-12-21 01:49:56 +08:00 • committed by Gary Linscott
parent 9cae6e66ce
commit 3231038262
1 changed files with 32 additions and 22 deletions
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54
src/pawns.cpp
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@ -60,23 +60,36 @@ namespace {
// Unsupported pawn penalty
const Score UnsupportedPawnPenalty = S(20, 10);
// Weakness of our pawn shelter in front of the king indexed by [rank]
const Value ShelterWeakness[RANK_NB] =
{ V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
// Weakness of our pawn shelter in front of the king indexed by [file pairs (a/h,b/g,c/f,d/e)][rank]
const Value ShelterWeakness[][RANK_NB] = {
{ V(101), V(10), V(24), V(68), V(90), V( 95), V(102) },
{ V(105), V( 1), V(30), V(76), V(95), V(100), V(105) },
{ V( 99), V( 0), V(32), V(72), V(92), V(101), V(100) },
{ V( 94), V( 1), V(31), V(68), V(89), V( 98), V(106) } };
// Danger of enemy pawns moving toward our king indexed by
// [edge files][no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
const Value StormDanger[][3][RANK_NB] = {
{ { V( 0), V(64), V(128), V(51), V(26) },
{ V(26), V(32), V( 96), V(38), V(20) },
{ V( 0), V( 0), V(160), V(25), V(13) } },
{ { V( 0), V(64), V(128), V(51), V(26) },
{ V(26), V(32), V( 96), V(38), V(20) },
{ V( 0), V( 0), V( 80), V(13), V( 7) } } };
// [file pairs (a/h,b/g,c/f,d/e)][no friendly pawn | pawn unblocked | pawn blocked by pawn| pawn blocked by king][rank of enemy pawn]
const Value StormDanger[][4][RANK_NB] = {
{ { V( 0), V( 61), V( 128), V(47), V(27) },
{ V(25), V( 33), V( 95), V(39), V(21) },
{ V( 0), V( 0), V( 80), V(14), V( 8) },
{ V( 0), V(-300), V(-300), V(54), V(23) } },
{ { V( 0), V( 66), V( 131), V(49), V(27) },
{ V(24), V( 33), V( 97), V(42), V(22) },
{ V( 0), V( 0), V( 163), V(28), V(12) },
{ V( 0), V( 67), V( 128), V(46), V(24) } },
{ { V( 0), V( 62), V( 126), V(52), V(23) },
{ V(24), V( 33), V( 93), V(35), V(23) },
{ V( 0), V( 0), V( 163), V(25), V(15) },
{ V( 0), V( 64), V( 130), V(50), V(29) } },
{ { V( 0), V( 63), V( 128), V(52), V(26) },
{ V(26), V( 27), V( 96), V(37), V(22) },
{ V( 0), V( 0), V( 161), V(24), V(14) },
{ V( 0), V( 63), V( 127), V(51), V(24) } } };
// Max bonus for king safety. Corresponds to start position with all the pawns
// in front of the king and no enemy pawn on the horizon.
const Value MaxSafetyBonus = V(263);
const Value MaxSafetyBonus = V(261);
#undef S
#undef V
@ -233,7 +246,6 @@ template<Color Us>
Value Entry::shelter_storm(const Position& pos, Square ksq) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
const Bitboard Edges = (FileABB | FileHBB) & (Rank2BB | Rank3BB);
Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq));
Bitboard ourPawns = b & pos.pieces(Us);
@ -249,15 +261,13 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
b = theirPawns & file_bb(f);
Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
if ( (Edges & make_square(f, rkThem))
&& file_of(ksq) == f
&& relative_rank(Us, ksq) == rkThem - 1)
safety += 200;
else
safety -= ShelterWeakness[rkUs]
+ StormDanger[f == FILE_A || f == FILE_H]
[rkUs == RANK_1 ? 0 :
rkThem != rkUs + 1 ? 1 : 2][rkThem];
safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs]
+ StormDanger[std::min(f, FILE_H - f)]
[file_of(ksq) == f && relative_rank(Us, ksq) == rkThem - 1 ? 3 :
rkUs == RANK_1 ? 0 :
rkThem != rkUs + 1 ? 1 :
/* pawn blocked by pawn */ 2 ]
[rkThem];
}
return safety;