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Use a std::bitset for KPKBitbase

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This is a non-functional simplification. Looks like std::bitset works good
for the KPKBitbase. Thanks for Jorg Oster for helping get the speed up
(the [] accessor is faster than test()).

Speed testing: 10k calls to probe:
  master 9.8 sec
  patch 9.8 sec.

STC
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 100154 W: 19025 L: 18992 D: 62137
Ptnml(0-2): 1397, 11376, 24572, 11254, 1473
http://tests.stockfishchess.org/tests/view/5e21e601346e35ac603b7d2b

Closes https://github.com/official-stockfish/Stockfish/pull/2502

No functional change
This commit is contained in:
protonspring 2020-01-23 18:18:58 +01:00 • committed by Stéphane Nicolet
parent f3c83ed46c
commit 6f1013794c
1 changed files with 5 additions and 6 deletions
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11
src/bitbase.cpp
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@ -21,6 +21,7 @@
#include <cassert>
#include <numeric>
#include <vector>
#include <bitset>
#include "bitboard.h"
#include "types.h"
@ -31,8 +32,7 @@ namespace {
// 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<MAX_INDEX> KPKBitbase;
// A KPK bitbase index is an integer in [0, IndexMax] range
//
@ -74,8 +74,7 @@ bool Bitbases::probe(Square wksq, Square wpsq, Square bksq, Color stm) {
assert(file_of(wpsq) <= FILE_D);
unsigned idx = index(stm, bksq, wksq, wpsq);
return KPKBitbase[idx / 32] & (1 << (idx & 0x1F));
return KPKBitbase[index(stm, bksq, wksq, wpsq)];
}
@ -94,10 +93,10 @@ void Bitbases::init() {
for (repeat = idx = 0; idx < MAX_INDEX; ++idx)
repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN);
// Map 32 results into one KPKBitbase[] entry
// Fill the bitbase with the decisive results
for (idx = 0; idx < MAX_INDEX; ++idx)
if (db[idx] == WIN)
KPKBitbase[idx / 32] |= 1 << (idx & 0x1F);
KPKBitbase.set(idx);
}