mirror of
https://github.com/sockspls/badfish
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fa143922ae
Current logic can apply Null move pruning
on a dead-lost position returning an unproven loss
(i.e. in TB loss score or mated in losing score) on nonPv nodes.
on a default bench, this can be observed by adding this debugging line:
```
if (nullValue >= beta)
{
// Do not return unproven mate or TB scores
nullValue = std::min(nullValue, VALUE_TB_WIN_IN_MAX_PLY-1);
dbg_hit_on(nullValue <= VALUE_TB_LOSS_IN_MAX_PLY); // Hit #0: Total 73983 Hits 1 Hit Rate (%) 0.00135166
if (thisThread->nmpMinPly || depth < 14)
return nullValue;
```
This fixes this very rare issue (happens at ~0.00135166% of the time) by
eliminating the need to try Null Move Pruning with dead-lost positions
and leaving it to be determined by a normal searching flow.
The previous try to fix was not as safe enough because it was capping
the returned value to (out of TB range) thus reviving the dead-lost position
based on an artificial clamp (i.e. the in TB score/mate score can be lost on that nonPv node):
https://tests.stockfishchess.org/tests/view/649756d5dc7002ce609cd794
Final fix:
Passed STC:
https://tests.stockfishchess.org/tests/view/649a5446dc7002ce609d1049
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 577280 W: 153613 L: 153965 D: 269702
Ptnml(0-2): 1320, 60594, 165190, 60190, 1346
Passed LTC:
https://tests.stockfishchess.org/tests/view/649cd048dc7002ce609d4801
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 246432 W: 66769 L: 66778 D: 112885
Ptnml(0-2): 83, 22105, 78847, 22100, 81
closes https://github.com/official-stockfish/Stockfish/pull/4649
Bench: 2425978
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| .. | ||
| incbin | ||
| nnue | ||
| syzygy | ||
| benchmark.cpp | ||
| benchmark.h | ||
| bitbase.cpp | ||
| bitboard.cpp | ||
| bitboard.h | ||
| endgame.cpp | ||
| endgame.h | ||
| evaluate.cpp | ||
| evaluate.h | ||
| main.cpp | ||
| Makefile | ||
| material.cpp | ||
| material.h | ||
| misc.cpp | ||
| misc.h | ||
| movegen.cpp | ||
| movegen.h | ||
| movepick.cpp | ||
| movepick.h | ||
| pawns.cpp | ||
| pawns.h | ||
| position.cpp | ||
| position.h | ||
| psqt.cpp | ||
| psqt.h | ||
| search.cpp | ||
| search.h | ||
| thread.cpp | ||
| thread.h | ||
| thread_win32_osx.h | ||
| timeman.cpp | ||
| timeman.h | ||
| tt.cpp | ||
| tt.h | ||
| tune.cpp | ||
| tune.h | ||
| types.h | ||
| uci.cpp | ||
| uci.h | ||
| ucioption.cpp | ||