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Apex Pawns

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Pawns which are supported already have a bonus. Apex are pawns which are
supported twice.
This patch gives an additional 50% bonus for them.

STC
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 6549 W: 1333 L: 1209 D: 4007

LTC
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 18002 W: 3037 L: 2850 D: 12115

Bench: 8069601

Resolves #267
This commit is contained in:
Alain SAVARD 2015-02-27 01:50:35 +08:00 • committed by Gary Linscott
parent e2226cbb20
commit fce799294c
1 changed files with 13 additions and 9 deletions
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22
src/pawns.cpp
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@ -110,9 +110,9 @@ namespace {
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
Bitboard b, p, doubled, connected;
Bitboard b, p, doubled, connected, supported;
Square s;
bool passed, isolated, opposed, phalanx, backward, unsupported, lever;
bool passed, isolated, opposed, phalanx, backward, lever;
Score score = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
@ -138,13 +138,12 @@ namespace {
e->semiopenFiles[Us] &= ~(1 << f);
// Previous rank
p = rank_bb(s - pawn_push(Us));
p = rank_bb(s - Up);
// Flag the pawn as passed, isolated, doubled,
// unsupported or connected (but not the backward one).
// Flag the pawn
connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p);
phalanx = connected & rank_bb(s);
unsupported = !(ourPawns & adjacent_files_bb(f) & p);
supported = connected & p;
isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & forward_bb(Us, s);
opposed = theirPawns & forward_bb(Us, s);
@ -160,7 +159,7 @@ namespace {
backward = false;
else
{
// We now know that there are no friendly pawns beside or behind this
// We now know there are no friendly pawns beside or behind this
// pawn on adjacent files. We now check whether the pawn is
// backward by looking in the forward direction on the adjacent
// files, and picking the closest pawn there.
@ -184,7 +183,7 @@ namespace {
if (isolated)
score -= Isolated[opposed][f];
if (unsupported && !isolated)
if (!supported && !isolated)
score -= UnsupportedPawnPenalty;
if (doubled)
@ -193,8 +192,13 @@ namespace {
if (backward)
score -= Backward[opposed][f];
if (connected)
if (connected) {
score += Connected[opposed][phalanx][relative_rank(Us, s)];
if (more_than_one(supported)) {
//apex bonus: pawn on s is supported twice
score += Connected[opposed][phalanx][relative_rank(Us, s)] / 2;
}
}
if (lever)
score += Lever[relative_rank(Us, s)];