X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=ed6ed2088e19b3c0bd5e19278645ea151ba0b1be;hp=ebf3c59a02355d780e31d79b48d8e70c36ee7d6c;hb=6f1013794cecc179e7432004b8555e64ddca75a5;hpb=be509525336b65419e708678abe4e16efb5f6f4d
diff --git a/src/bitbase.cpp b/src/bitbase.cpp
index ebf3c59a..ed6ed208 100644
--- a/src/bitbase.cpp
+++ b/src/bitbase.cpp
@@ -2,6 +2,7 @@
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -17,21 +18,21 @@
along with this program. If not, see .
*/
-#include
#include
#include
#include
+#include
#include "bitboard.h"
#include "types.h"
namespace {
- // There are 24 possible pawn squares: the first 4 files and ranks from 2 to 7
- const unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
+ // There are 24 possible pawn squares: files A to D and ranks from 2 to 7.
+ // Positions with the pawn on files E to H will be mirrored before probing.
+ constexpr unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
- // Each uint32_t stores results of 32 positions, one per bit
- uint32_t KPKBitbase[MAX_INDEX / 32];
+ std::bitset KPKBitbase;
// A KPK bitbase index is an integer in [0, IndexMax] range
//
@@ -42,8 +43,8 @@ namespace {
// bit 12: side to move (WHITE or BLACK)
// bit 13-14: white pawn file (from FILE_A to FILE_D)
// bit 15-17: white pawn RANK_7 - rank (from RANK_7 - RANK_7 to RANK_7 - RANK_2)
- unsigned index(Color us, Square bksq, Square wksq, Square psq) {
- return wksq | (bksq << 6) | (us << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15);
+ unsigned index(Color stm, Square bksq, Square wksq, Square psq) {
+ return int(wksq) | (bksq << 6) | (stm << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15);
}
enum Result {
@@ -53,19 +54,15 @@ namespace {
WIN = 4
};
- inline Result& operator|=(Result& r, Result v) { return r = Result(r | v); }
+ Result& operator|=(Result& r, Result v) { return r = Result(r | v); }
struct KPKPosition {
KPKPosition() = default;
explicit KPKPosition(unsigned idx);
operator Result() const { return result; }
- Result classify(const std::vector& db)
- { return us == WHITE ? classify(db) : classify(db); }
+ Result classify(const std::vector& db);
- template Result classify(const std::vector& db);
-
- unsigned id;
- Color us;
+ Color stm;
Square ksq[COLOR_NB], psq;
Result result;
};
@@ -73,31 +70,33 @@ namespace {
} // namespace
-bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color us) {
+bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color stm) {
assert(file_of(wpsq) <= FILE_D);
- unsigned idx = index(us, bksq, wksq, wpsq);
- return KPKBitbase[idx / 32] & (1 << (idx & 0x1F));
+ return KPKBitbase[index(stm, bksq, wksq, wpsq)];
}
void Bitbases::init() {
std::vector db(MAX_INDEX);
+ unsigned idx, repeat = 1;
// Initialize db with known win / draw positions
- std::generate(db.begin(), db.end(), [](){ static unsigned id; return KPKPosition(id++); });
+ for (idx = 0; idx < MAX_INDEX; ++idx)
+ db[idx] = KPKPosition(idx);
// Iterate through the positions until none of the unknown positions can be
// changed to either wins or draws (15 cycles needed).
- while (std::accumulate(db.begin(), db.end(), false, [&](bool repeat, KPKPosition& pos)
- { return (pos == UNKNOWN && pos.classify(db) != UNKNOWN) || repeat; })){}
-
- // Map 32 results into one KPKBitbase[] entry
- for (auto& pos : db)
- if (pos == WIN)
- KPKBitbase[pos.id / 32] |= 1 << (pos.id & 0x1F);
+ while (repeat)
+ for (repeat = idx = 0; idx < MAX_INDEX; ++idx)
+ repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN);
+
+ // Fill the bitbase with the decisive results
+ for (idx = 0; idx < MAX_INDEX; ++idx)
+ if (db[idx] == WIN)
+ KPKBitbase.set(idx);
}
@@ -105,31 +104,30 @@ namespace {
KPKPosition::KPKPosition(unsigned idx) {
- id = idx;
ksq[WHITE] = Square((idx >> 0) & 0x3F);
ksq[BLACK] = Square((idx >> 6) & 0x3F);
- us = Color ((idx >> 12) & 0x01);
- psq = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7));
+ stm = Color ((idx >> 12) & 0x01);
+ psq = make_square(File((idx >> 13) & 0x3), Rank(RANK_7 - ((idx >> 15) & 0x7)));
// Check if two pieces are on the same square or if a king can be captured
if ( distance(ksq[WHITE], ksq[BLACK]) <= 1
|| ksq[WHITE] == psq
|| ksq[BLACK] == psq
- || (us == WHITE && (StepAttacksBB[PAWN][psq] & ksq[BLACK])))
+ || (stm == WHITE && (PawnAttacks[WHITE][psq] & ksq[BLACK])))
result = INVALID;
// Immediate win if a pawn can be promoted without getting captured
- else if ( us == WHITE
+ else if ( stm == WHITE
&& rank_of(psq) == RANK_7
- && ksq[us] != psq + DELTA_N
- && ( distance(ksq[~us], psq + DELTA_N) > 1
- || (StepAttacksBB[KING][ksq[us]] & (psq + DELTA_N))))
+ && ksq[stm] != psq + NORTH
+ && ( distance(ksq[~stm], psq + NORTH) > 1
+ || (PseudoAttacks[KING][ksq[stm]] & (psq + NORTH))))
result = WIN;
// Immediate draw if it is a stalemate or a king captures undefended pawn
- else if ( us == BLACK
- && ( !(StepAttacksBB[KING][ksq[us]] & ~(StepAttacksBB[KING][ksq[~us]] | StepAttacksBB[PAWN][psq]))
- || (StepAttacksBB[KING][ksq[us]] & psq & ~StepAttacksBB[KING][ksq[~us]])))
+ else if ( stm == BLACK
+ && ( !(PseudoAttacks[KING][ksq[stm]] & ~(PseudoAttacks[KING][ksq[~stm]] | PawnAttacks[~stm][psq]))
+ || (PseudoAttacks[KING][ksq[stm]] & psq & ~PseudoAttacks[KING][ksq[~stm]])))
result = DRAW;
// Position will be classified later
@@ -137,7 +135,6 @@ namespace {
result = UNKNOWN;
}
- template
Result KPKPosition::classify(const std::vector& db) {
// White to move: If one move leads to a position classified as WIN, the result
@@ -149,27 +146,25 @@ namespace {
// of the current position is DRAW. If all moves lead to positions classified
// as WIN, the position is classified as WIN, otherwise the current position is
// classified as UNKNOWN.
-
- const Color Them = (Us == WHITE ? BLACK : WHITE);
- const Result Good = (Us == WHITE ? WIN : DRAW);
- const Result Bad = (Us == WHITE ? DRAW : WIN);
+ const Result Good = (stm == WHITE ? WIN : DRAW);
+ const Result Bad = (stm == WHITE ? DRAW : WIN);
Result r = INVALID;
- Bitboard b = StepAttacksBB[KING][ksq[Us]];
+ Bitboard b = PseudoAttacks[KING][ksq[stm]];
while (b)
- r |= Us == WHITE ? db[index(Them, ksq[Them] , pop_lsb(&b), psq)]
- : db[index(Them, pop_lsb(&b), ksq[Them] , psq)];
+ r |= stm == WHITE ? db[index(BLACK, ksq[BLACK] , pop_lsb(&b), psq)]
+ : db[index(WHITE, pop_lsb(&b), ksq[WHITE], psq)];
- if (Us == WHITE)
+ if (stm == WHITE)
{
if (rank_of(psq) < RANK_7) // Single push
- r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N)];
+ r |= db[index(BLACK, ksq[BLACK], ksq[WHITE], psq + NORTH)];
if ( rank_of(psq) == RANK_2 // Double push
- && psq + DELTA_N != ksq[Us]
- && psq + DELTA_N != ksq[Them])
- r |= db[index(Them, ksq[Them], ksq[Us], psq + DELTA_N + DELTA_N)];
+ && psq + NORTH != ksq[WHITE]
+ && psq + NORTH != ksq[BLACK])
+ r |= db[index(BLACK, ksq[BLACK], ksq[WHITE], psq + NORTH + NORTH)];
}
return result = r & Good ? Good : r & UNKNOWN ? UNKNOWN : Bad;