{ S(20, 28), S(29, 31), S(33, 31), S(33, 31),
S(33, 31), S(33, 31), S(29, 31), S(20, 28) } };
- // Connected bonus by rank
- const int Connected[RANK_NB] = {0, 6, 15, 10, 57, 75, 135, 258};
+ // Connected pawn bonus by opposed, phalanx flags and rank
+ Score Connected[2][2][RANK_NB];
// Levers bonus by rank
const Score Lever[RANK_NB] = {
S( 0, 0), S( 0, 0), S(0, 0), S(0, 0),
S(20,20), S(40,40), S(0, 0), S(0, 0) };
- // Bonus for file distance of the two outermost pawns
- const Score PawnsFileSpan = S(0, 15);
-
// Unsupported pawn penalty
const Score UnsupportedPawnPenalty = S(20, 10);
{ V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
// Danger of enemy pawns moving toward our king indexed by
- // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn]
- const Value StormDanger[][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) } };
+ // [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) } } };
// 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 Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b, p, doubled;
+ Bitboard b, p, doubled, connected;
Square s;
- bool passed, isolated, opposed, connected, backward, unsupported, lever;
+ bool passed, isolated, opposed, phalanx, backward, unsupported, lever;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
- Rank r = rank_of(s), rr = relative_rank(Us, s);
File f = file_of(s);
// This file cannot be semi-open
// Previous rank
p = rank_bb(s - pawn_push(Us));
- // 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;
+ connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p);
+ phalanx = connected & rank_bb(s);
unsupported = !(ourPawns & adjacent_files_bb(f) & p);
isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & forward_bb(Us, s);
value -= UnsupportedPawnPenalty;
if (doubled)
- value -= Doubled[f] / rank_distance(s, lsb(doubled));
+ value -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
if (backward)
value -= Backward[opposed][f];
- if (connected) {
- int bonus = Connected[rr];
- if (ourPawns & adjacent_files_bb(f) & rank_bb(r))
- bonus += (Connected[rr+1] - Connected[rr]) / 2;
- value += make_score(bonus / 2, bonus >> opposed);
- }
+ if (connected)
+ value += Connected[opposed][phalanx][relative_rank(Us, s)];
if (lever)
- value += Lever[rr];
+ value += Lever[relative_rank(Us, s)];
}
b = e->semiopenFiles[Us] ^ 0xFF;
e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0;
- // In endgame it's better to have pawns on both wings. So give a bonus according
- // to file distance between left and right outermost pawns.
- value += PawnsFileSpan * e->pawnSpan[Us];
-
return value;
}
namespace Pawns {
+/// init() initializes some tables used by evaluation. Instead of hard-coded
+/// tables, when makes sense, we prefer to calculate them with a formula to
+/// reduce independent parameters and to allow easier tuning and better insight.
+
+void init()
+{
+ static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 };
+
+ for (int opposed = 0; opposed <= 1; ++opposed)
+ 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);
+ }
+}
+
+
/// probe() takes a position as input, computes a Entry object, and returns a
/// pointer to it. The result is also stored in a hash table, so we don't have
/// to recompute everything when the same pawn structure occurs again.
safety += 200;
else
safety -= ShelterWeakness[rkUs]
- + StormDanger[rkUs == RANK_1 ? 0 :
+ + StormDanger[f == FILE_A || f == FILE_H]
+ [rkUs == RANK_1 ? 0 :
rkThem != rkUs + 1 ? 1 : 2][rkThem];
}
kingSquares[Us] = ksq;
castlingRights[Us] = pos.can_castle(Us);
- minKPdistance[Us] = 0;
+ minKingPawnDistance[Us] = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
if (pawns)
- while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
+ while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
- return make_score(0, -16 * minKPdistance[Us]);
+ return make_score(0, -16 * minKingPawnDistance[Us]);
Value bonus = shelter_storm<Us>(pos, ksq);
if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
- return make_score(bonus, -16 * minKPdistance[Us]);
+ return make_score(bonus, -16 * minKingPawnDistance[Us]);
}
// Explicit template instantiation
projects / stockfish / blobdiff