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Introduce penalty for weak (=unsupported) pawns.

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We add a penalty for each pawn which is not protected by another pawn
of the same color.

Passed both short TC
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 12107 W: 2411 L: 2272 D: 7424

And long TC
LLR: 2.96 (-2.94,2.94) [0.00,6.00]
Total: 9204 W: 1605 L: 1458 D: 6141

bench: 7682173
This commit is contained in:
snicolet 2014-03-23 23:51:25 +01:00 • committed by Marco Costalba
parent 9e72e35942
commit e7362dae78
1 changed files with 21 additions and 11 deletions
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32
src/pawns.cpp
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@ -60,6 +60,9 @@ namespace {
// Bonus for file distance of the two outermost pawns
const Score PawnsFileSpan = S(0, 15);
// 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) };
@ -86,10 +89,10 @@ namespace {
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
Bitboard b;
Bitboard b, p;
Square s;
File f;
bool passed, isolated, doubled, opposed, connected, backward, candidate;
bool passed, isolated, doubled, opposed, connected, backward, candidate, unsupported;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
@ -113,16 +116,20 @@ namespace {
// This file cannot be semi-open
e->semiopenFiles[Us] &= ~(1 << f);
// Our rank plus previous one
b = rank_bb(s) | rank_bb(s - pawn_push(Us));
// Previous rank
p = rank_bb(s - pawn_push(Us));
// Flag the pawn as passed, isolated, doubled or
// connected (but not the backward one).
connected = ourPawns & adjacent_files_bb(f) & b;
isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & forward_bb(Us, s);
opposed = theirPawns & forward_bb(Us, s);
passed = !(theirPawns & passed_pawn_mask(Us, s));
// Our rank plus previous one
b = rank_bb(s) | p;
// Flag the pawn as passed, isolated, doubled,
// unsupported or connected (but not the backward one).
connected = ourPawns & adjacent_files_bb(f) & b;
unsupported = !(ourPawns & adjacent_files_bb(f) & p);
isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & forward_bb(Us, s);
opposed = theirPawns & forward_bb(Us, s);
passed = !(theirPawns & passed_pawn_mask(Us, s));
// Test for backward pawn.
// If the pawn is passed, isolated, or connected it cannot be
@ -166,6 +173,9 @@ namespace {
if (isolated)
value -= Isolated[opposed][f];
if (unsupported && !isolated)
value -= UnsupportedPawnPenalty;
if (doubled)
value -= Doubled[f];