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Use 128 bit multiply for TT index

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Remove super cluster stuff from TT and just use a 128 bit multiply.

STC https://tests.stockfishchess.org/tests/view/5ee719b3aae8aec816ab7548
LLR: 2.94 (-2.94,2.94) {-1.50,0.50}
Total: 12736 W: 2502 L: 2333 D: 7901
Ptnml(0-2): 191, 1452, 2944, 1559, 222

LTC https://tests.stockfishchess.org/tests/view/5ee732d1aae8aec816ab7556
LLR: 2.93 (-2.94,2.94) {-1.50,0.50}
Total: 27584 W: 3431 L: 3350 D: 20803
Ptnml(0-2): 173, 2500, 8400, 2511, 208

Scheme back to being derived from https://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/

Also the default optimized version of the index calculation now uses fewer instructions.
https://godbolt.org/z/Tktxbv
Might benefit from mulx (requires -mbmi2)

closes https://github.com/official-stockfish/Stockfish/pull/2744

bench: 4320954
This commit is contained in:
mstembera
2020-06-14 23:35:07 -07:00
committed by Joost VandeVondele
parent 995ee4b311
commit 1ea488d34c
5 changed files with 22 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
src/misc.h
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@@ -110,6 +110,19 @@ public:
{ return T(rand64() & rand64() & rand64()); }
};
inline uint64_t mul_hi64(uint64_t a, uint64_t b) {
#if defined(__GNUC__) && defined(IS_64BIT)
__extension__ typedef unsigned __int128 uint128;
return ((uint128)a * (uint128)b) >> 64;
#else
uint64_t aL = (uint32_t)a, aH = a >> 32;
uint64_t bL = (uint32_t)b, bH = b >> 32;
uint64_t c1 = (aL * bL) >> 32;
uint64_t c2 = aH * bL + c1;
uint64_t c3 = aL * bH + (uint32_t)c2;
return aH * bH + (c2 >> 32) + (c3 >> 32);
#endif
}
/// Under Windows it is not possible for a process to run on more than one
/// logical processor group. This usually means to be limited to use max 64