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https://github.com/sockspls/badfish
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Assorted code style and comments in pawns.cpp and pawns.h
The only interesting thing is that a backward or isolated pawn cannot be a candidate passer, so code this condition. No functional change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
parent
8e71ee7ec6
commit
2f1935078d
4 changed files with 65 additions and 83 deletions
101
src/pawns.cpp
101
src/pawns.cpp
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@ -17,27 +17,15 @@
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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////
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//// Includes
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////
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#include <cassert>
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#include <cstring>
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#include "bitboard.h"
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#include "bitcount.h"
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#include "pawns.h"
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#include "position.h"
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////
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//// Local definitions
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////
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namespace {
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/// Constants and variables
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#define S(mg, eg) make_score(mg, eg)
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// Doubled pawn penalty by opposed flag and file
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@ -77,14 +65,9 @@ namespace {
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}
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////
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//// Functions
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////
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/// PawnInfoTable::get_pawn_info() takes a position object as input, computes
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/// a PawnInfo object, and returns a pointer to it. The result is also stored
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/// in a hash table, so we don't have to recompute everything when the same
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/// in an hash table, so we don't have to recompute everything when the same
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/// pawn structure occurs again.
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PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
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@ -100,11 +83,11 @@ PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
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if (pi->key == key)
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return pi;
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// Clear the PawnInfo object, and set the key
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memset(pi, 0, sizeof(PawnInfo));
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pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
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pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
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// Initialize PawnInfo entry
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pi->key = key;
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pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0;
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pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
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pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
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// Calculate pawn attacks
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Bitboard wPawns = pos.pieces(PAWN, WHITE);
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@ -124,13 +107,16 @@ PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
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template<Color Us>
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Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
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Bitboard theirPawns, PawnInfo* pi) const {
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const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
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const Color Them = (Us == WHITE ? BLACK : WHITE);
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Bitboard b;
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Square s;
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File f;
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Rank r;
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bool passed, isolated, doubled, opposed, chain, backward, candidate;
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Score value = SCORE_ZERO;
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const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
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const Square* ptr = pos.piece_list_begin(Us, PAWN);
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// Loop through all pawns of the current color and score each pawn
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@ -144,11 +130,11 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
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// This file cannot be half open
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pi->halfOpenFiles[Us] &= ~(1 << f);
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// Our rank plus previous one. Used for chain detection.
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// Our rank plus previous one. Used for chain detection
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b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
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// Passed, isolated, doubled or member of a pawn
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// chain (but not the backward one) ?
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// Flag the pawn as passed, isolated, doubled or member of a pawn
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// chain (but not the backward one).
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passed = !(theirPawns & passed_pawn_mask(Us, s));
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doubled = ourPawns & squares_in_front_of(Us, s);
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opposed = theirPawns & squares_in_front_of(Us, s);
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@ -156,15 +142,13 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
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chain = ourPawns & neighboring_files_bb(f) & b;
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// Test for backward pawn
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//
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backward = false;
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// If the pawn is passed, isolated, or member of a pawn chain
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// it cannot be backward. If can capture an enemy pawn or if
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// there are friendly pawns behind on neighboring files it cannot
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// be backward either.
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// If the pawn is passed, isolated, or member of a pawn chain it cannot
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// be backward. If there are friendly pawns behind on neighboring files
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// or if can capture an enemy pawn it cannot be backward either.
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if ( !(passed | isolated | chain)
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&& !(ourPawns & attack_span_mask(opposite_color(Us), s))
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&& !(ourPawns & attack_span_mask(Them, s))
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&& !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
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{
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// We now know that there are no friendly pawns beside or behind this
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@ -178,21 +162,24 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
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while (!(b & (ourPawns | theirPawns)))
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Us == WHITE ? b <<= 8 : b >>= 8;
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// The friendly pawn needs to be at least two ranks closer than the enemy
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// pawn in order to help the potentially backward pawn advance.
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// The friendly pawn needs to be at least two ranks closer than the
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// enemy pawn in order to help the potentially backward pawn advance.
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backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
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}
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assert(passed | opposed | (attack_span_mask(Us, s) & theirPawns));
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assert(opposed | passed | (attack_span_mask(Us, s) & theirPawns));
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// Test for candidate passed pawn
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candidate = !(opposed | passed)
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&& (b = attack_span_mask(opposite_color(Us), s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
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// A not passed pawn is a candidate to become passed if it is free to
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// advance and if the number of friendly pawns beside or behind this
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// pawn on neighboring files is higher or equal than the number of
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// enemy pawns in the forward direction on the neighboring files.
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candidate = !(opposed | passed | backward | isolated)
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&& (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
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&& count_1s<Max15>(b) >= count_1s<Max15>(attack_span_mask(Us, s) & theirPawns);
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// Mark the pawn as passed. Pawn will be properly scored in evaluation
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// because we need full attack info to evaluate passed pawns. Only the
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// frontmost passed pawn on each file is considered a true passed pawn.
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// Passed pawns will be properly scored in evaluation because we need
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// full attack info to evaluate passed pawns. Only the frontmost passed
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// pawn on each file is considered a true passed pawn.
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if (passed && !doubled)
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set_bit(&(pi->passedPawns[Us]), s);
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@ -214,3 +201,33 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
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}
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return value;
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}
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/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
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/// only when king square changes, about 20% of total king_shelter() calls.
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template<Color Us>
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Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
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const int Shift = (Us == WHITE ? 8 : -8);
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Bitboard pawns;
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int r, shelter = 0;
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if (relative_rank(Us, ksq) <= RANK_4)
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{
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pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
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r = ksq & (7 << 3);
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for (int i = 0; i < 3; i++)
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{
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r += Shift;
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shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (64 >> i);
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}
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}
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kingSquares[Us] = ksq;
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kingShelters[Us] = make_score(shelter, 0);
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return kingShelters[Us];
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}
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// Explicit template instantiation
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template Score PawnInfo::updateShelter<WHITE>(const Position& pos, Square ksq);
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template Score PawnInfo::updateShelter<BLACK>(const Position& pos, Square ksq);
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42
src/pawns.h
42
src/pawns.h
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@ -20,7 +20,6 @@
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#if !defined(PAWNS_H_INCLUDED)
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#define PAWNS_H_INCLUDED
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#include "bitboard.h"
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#include "position.h"
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#include "tt.h"
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#include "types.h"
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@ -66,28 +65,14 @@ private:
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/// method is get_pawn_info, which returns a pointer to a PawnInfo object.
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class PawnInfoTable : public SimpleHash<PawnInfo, PawnTableSize> {
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enum SideType { KingSide, QueenSide };
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public:
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PawnInfo* get_pawn_info(const Position& pos) const;
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void prefetch(Key key) const;
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private:
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template<Color Us>
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Score evaluate_pawns(const Position& pos, Bitboard ourPawns, Bitboard theirPawns, PawnInfo* pi) const;
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};
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inline Square pawn_push(Color c) {
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return c == WHITE ? DELTA_N : DELTA_S;
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}
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inline void PawnInfoTable::prefetch(Key key) const {
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unsigned index = unsigned(key & (PawnTableSize - 1));
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PawnInfo* pi = entries + index;
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::prefetch((char*) pi);
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}
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inline Score PawnInfo::pawns_value() const {
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return value;
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@ -102,7 +87,7 @@ inline Bitboard PawnInfo::passed_pawns(Color c) const {
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}
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inline int PawnInfo::file_is_half_open(Color c, File f) const {
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return (halfOpenFiles[c] & (1 << int(f)));
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return halfOpenFiles[c] & (1 << int(f));
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}
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inline int PawnInfo::has_open_file_to_left(Color c, File f) const {
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@ -113,31 +98,6 @@ inline int PawnInfo::has_open_file_to_right(Color c, File f) const {
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return halfOpenFiles[c] & ~((1 << int(f+1)) - 1);
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}
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/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
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/// only when king square changes, about 20% of total king_shelter() calls.
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template<Color Us>
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Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
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const int Shift = (Us == WHITE ? 8 : -8);
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Bitboard pawns;
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int r, shelter = 0;
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if (relative_rank(Us, ksq) <= RANK_4)
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{
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pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
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r = square_rank(ksq) * 8;
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for (int i = 1; i < 4; i++)
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{
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r += Shift;
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shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
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}
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}
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kingSquares[Us] = ksq;
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kingShelters[Us] = make_score(shelter, 0);
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return kingShelters[Us];
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}
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template<Color Us>
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inline Score PawnInfo::king_shelter(const Position& pos, Square ksq) {
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return kingSquares[Us] == ksq ? kingShelters[Us] : updateShelter<Us>(pos, ksq);
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1
src/tt.h
1
src/tt.h
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@ -51,6 +51,7 @@ public:
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virtual ~SimpleHash() { delete [] entries; }
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Entry* find(Key key) const { return entries + ((uint32_t)key & (HashSize - 1)); }
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void prefetch(Key key) const { ::prefetch((char*)find(key)); }
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protected:
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Entry* entries;
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@ -463,4 +463,8 @@ inline bool square_is_ok(Square s) {
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return s >= SQ_A1 && s <= SQ_H8;
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}
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inline Square pawn_push(Color c) {
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return c == WHITE ? DELTA_N : DELTA_S;
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}
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#endif // !defined(TYPES_H_INCLUDED)
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