// Unsupported pawn penalty
const Score UnsupportedPawnPenalty = S(20, 10);
+ // Center bind bonus: Two pawns controlling the same central square
+ const Bitboard CenterBindMask[COLOR_NB] = {
+ (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB),
+ (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB)
+ };
+
+ const Score CenterBind = S(16, 0);
+
// Weakness of our pawn shelter in front of the king by [distance from edge][rank]
const Value ShelterWeakness[][RANK_NB] = {
{ V( 99), V(20), V(26), V(54), V(85), V( 92), V(108) },
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);
+ unsupported = !(connected & p);
isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & forward_bb(Us, s);
opposed = theirPawns & forward_bb(Us, s);
lever = theirPawns & pawnAttacksBB[s];
// Test for backward pawn.
- // If the pawn is passed, isolated, connected or a lever it cannot be
+ // If the pawn is passed, isolated, lever or connected it cannot be
// backward. If there are friendly pawns behind on adjacent files
// it cannot be backward either.
if ( (passed | isolated | lever | connected)
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.
b = e->semiopenFiles[Us] ^ 0xFF;
e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
+ // Center binds: Two pawns controlling the same central square
+ b = shift_bb<Right>(ourPawns) & shift_bb<Left>(ourPawns) & CenterBindMask[Us];
+ score += popcount<Max15>(b) * CenterBind;
+
return score;
}
for (int phalanx = 0; phalanx <= 1; ++phalanx)
for (Rank r = RANK_2; r < RANK_8; ++r)
{
- int bonus = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0);
- Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed);
+ int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
+ Connected[opposed][phalanx][r] = make_score( 3 * v / 2, v);
}
}