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Code Issues Releases Wiki Activity

Additional cleanup in bitbase.cpp

Browse source 
Also better document what code does.

No functional change.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2011-03-12 16:57:02 +01:00
parent c1c0984452
commit 635be39acf
2 changed files with 48 additions and 85 deletions
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131
src/bitbase.cpp
View file

@ -45,9 +45,11 @@ namespace {
Color sideToMove; Color sideToMove;
}; };
const int IndexMax = 2 * 24 * 64 * 64; // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7
const int IndexMax = 2 * 24 * 64 * 64; // color * wp_sq * wk_sq * bk_sq
uint8_t KPKBitbase[IndexMax / 8]; // Each uint32_t stores results of 32 positions, one per bit
uint32_t KPKBitbase[IndexMax / 32];
Result classify_wtm(const KPKPosition& pos, const Result bb[]); Result classify_wtm(const KPKPosition& pos, const Result bb[]);
Result classify_btm(const KPKPosition& pos, const Result bb[]); Result classify_btm(const KPKPosition& pos, const Result bb[]);
@ -55,23 +57,22 @@ namespace {
} }
int probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) { uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) {
int index = compute_index(wksq, bksq, wpsq, stm); int index = compute_index(wksq, bksq, wpsq, stm);
return KPKBitbase[index / 8] & (1 << (index & 7)); return KPKBitbase[index / 32] & (1 << (index & 31));
} }
void init_kpk_bitbase() { void init_kpk_bitbase() {
bool repeat;
int i, j, b;
KPKPosition pos;
Result bb[IndexMax]; Result bb[IndexMax];
KPKPosition pos;
bool repeat;
// Initialize table // Initialize table
for (i = 0; i < IndexMax; i++) for (int i = 0; i < IndexMax; i++)
{ {
pos.from_index(i); pos.from_index(i);
bb[i] = !pos.is_legal() ? RESULT_INVALID bb[i] = !pos.is_legal() ? RESULT_INVALID
@ -83,7 +84,7 @@ void init_kpk_bitbase() {
do { do {
repeat = false; repeat = false;
for (i = 0; i < IndexMax; i++) for (int i = 0; i < IndexMax; i++)
if (bb[i] == RESULT_UNKNOWN) if (bb[i] == RESULT_UNKNOWN)
{ {
pos.from_index(i); pos.from_index(i);
@ -96,29 +97,36 @@ void init_kpk_bitbase() {
} while (repeat); } while (repeat);
// Compress result and map into KPKBitbase[] // Map 32 position results into one KPKBitbase[] entry
for (i = 0; i < 24576; i++) for (int i = 0; i < IndexMax / 32; i++)
{ for (int j = 0; j < 32; j++)
b = 0; if (bb[32 * i + j] == RESULT_WIN || bb[32 * i + j] == RESULT_LOSS)
for (j = 0; j < 8; j++) KPKBitbase[i] |= (1 << j);
if (bb[8*i+j] == RESULT_WIN || bb[8*i+j] == RESULT_LOSS)
b |= (1 << j);
KPKBitbase[i] = (uint8_t)b;
}
} }
namespace { namespace {
// A KPK bitbase index is an integer in [0, IndexMax] range
//
// Information is mapped in this way
//
// bit 0: side to move (WHITE or BLACK)
// bit 1- 6: black king square (from SQ_A1 to SQ_H8)
// bit 7-12: white king square (from SQ_A1 to SQ_H8)
// bit 13-14: white pawn file (from FILE_A to FILE_D)
// bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1)
int compute_index(Square wksq, Square bksq, Square wpsq, Color stm) { int compute_index(Square wksq, Square bksq, Square wpsq, Color stm) {
int p = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4; assert(square_file(wpsq) <= FILE_D);
int r = int(stm) + 2 * int(bksq) + 128 * int(wksq) + 8192 * p;
assert(r >= 0 && r < IndexMax); int p = int(square_file(wpsq)) + 4 * int(square_rank(wpsq) - 1);
int r = int(stm) + 2 * int(bksq) + 128 * int(wksq) + 8192 * p;
return r; assert(r >= 0 && r < IndexMax);
return r;
} }
void KPKPosition::from_index(int index) { void KPKPosition::from_index(int index) {
@ -135,7 +143,7 @@ namespace {
if ( whiteKingSquare == pawnSquare if ( whiteKingSquare == pawnSquare
|| whiteKingSquare == blackKingSquare || whiteKingSquare == blackKingSquare
|| pawnSquare == blackKingSquare) || blackKingSquare == pawnSquare)
return false; return false;
if (sideToMove == WHITE) if (sideToMove == WHITE)
@ -167,16 +175,11 @@ namespace {
} }
else else
{ {
// Case 1: Stalemate // Case 1: Stalemate (possible pawn files are only from A to D)
if ( whiteKingSquare == SQ_A8 if ( whiteKingSquare == SQ_A8
&& pawnSquare == SQ_A7 && pawnSquare == SQ_A7
&& (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8)) && (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8))
return true; return true;
if ( whiteKingSquare == SQ_H8
&& pawnSquare == SQ_H7
&& (blackKingSquare == SQ_F7 || blackKingSquare == SQ_F8))
return true;
} }
return false; return false;
} }
@ -202,77 +205,47 @@ namespace {
bool unknownFound = false; bool unknownFound = false;
Bitboard b; Bitboard b;
Square s; Square s;
int idx; Result r;
// King moves // King moves
b = pos.wk_attacks(); b = pos.wk_attacks();
while (b) while (b)
{ {
s = pop_1st_bit(&b); s = pop_1st_bit(&b);
idx = compute_index(s, pos.blackKingSquare, pos.pawnSquare, BLACK); r = bb[compute_index(s, pos.blackKingSquare, pos.pawnSquare, BLACK)];
switch (bb[idx]) { if (r == RESULT_LOSS)
case RESULT_LOSS:
return RESULT_WIN; return RESULT_WIN;
case RESULT_UNKNOWN: if (r == RESULT_UNKNOWN)
unknownFound = true; unknownFound = true;
case RESULT_DRAW:
case RESULT_INVALID:
break;
default:
assert(false);
}
} }
// Pawn moves // Pawn moves
if (square_rank(pos.pawnSquare) < RANK_7) if (square_rank(pos.pawnSquare) < RANK_7)
{ {
s = pos.pawnSquare + DELTA_N; s = pos.pawnSquare + DELTA_N;
idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK); r = bb[compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK)];
switch (bb[idx]) { if (r == RESULT_LOSS)
case RESULT_LOSS:
return RESULT_WIN; return RESULT_WIN;
case RESULT_UNKNOWN: if (r == RESULT_UNKNOWN)
unknownFound = true; unknownFound = true;
case RESULT_DRAW:
case RESULT_INVALID:
break;
default:
assert(false);
}
// Double pawn push // Double pawn push
if ( square_rank(s) == RANK_3 if ( square_rank(s) == RANK_3
&& s != pos.whiteKingSquare && s != pos.whiteKingSquare
&& s != pos.blackKingSquare) && s != pos.blackKingSquare)
{ {
s += DELTA_N; s += DELTA_N;
idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK); r = bb[compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK)];
switch (bb[idx]) { if (r == RESULT_LOSS)
case RESULT_LOSS:
return RESULT_WIN; return RESULT_WIN;
case RESULT_UNKNOWN: if (r == RESULT_UNKNOWN)
unknownFound = true; unknownFound = true;
case RESULT_DRAW:
case RESULT_INVALID:
break;
default:
assert(false);
}
} }
} }
return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW; return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
@ -290,30 +263,20 @@ namespace {
bool unknownFound = false; bool unknownFound = false;
Bitboard b; Bitboard b;
Square s; Square s;
int idx; Result r;
// King moves // King moves
b = pos.bk_attacks(); b = pos.bk_attacks();
while (b) while (b)
{ {
s = pop_1st_bit(&b); s = pop_1st_bit(&b);
idx = compute_index(pos.whiteKingSquare, s, pos.pawnSquare, WHITE); r = bb[compute_index(pos.whiteKingSquare, s, pos.pawnSquare, WHITE)];
switch (bb[idx]) { if (r == RESULT_DRAW)
case RESULT_DRAW:
return RESULT_DRAW; return RESULT_DRAW;
case RESULT_UNKNOWN: if (r == RESULT_UNKNOWN)
unknownFound = true; unknownFound = true;
case RESULT_WIN:
case RESULT_INVALID:
break;
default:
assert(false);
}
} }
return unknownFound ? RESULT_UNKNOWN : RESULT_LOSS; return unknownFound ? RESULT_UNKNOWN : RESULT_LOSS;
} }

2
src/endgame.cpp
View file

@ -23,7 +23,7 @@
#include "endgame.h" #include "endgame.h"
#include "pawns.h" #include "pawns.h"
extern int probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm); extern uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm);
namespace { namespace {