Stockfish 16060715 - nowa wersja silnika szachowego UCI!

Stockfish - silnik szachowy UCI

Poprzednie wersje Stockfish

Autor kompilacji - Marco Costalba

Informacje o wersji:

Timestamp: 1465304786

Fix syzygy DTZ bug

In this position: 3K4/8/3k4/8/4p3/4B3/5P2/8 w - - 0 5

Current DTZ probe returns 1 instead of 15

What happens is that the double push f4 is erroneously detected as a win move.

After the push we have:

[D]3K4/8/3k4/8/4pP2/4B3/8/8 b - f3 0 5

And here the code misses the possible ep capture exf3.

The bug is in probe_dtz_no_ep() where is used probe_ab() that is

blind to ep captures so it returns v == 2 (win) for position

3K4/8/3k4/8/4pP2/4B3/8/8 b - f3 0 5

Note that at the caller site the original position did not have any

possible ep capture, so probe_dtz() returns immediately after calling

probe_dtz_no_ep().

The fix is to call the ep-aware probe_wdl() instead of probe_ab()

I have verified that DTZ is correct now and also there are no more

mistmatches compared to the new 'syzygy' branch. Tested on a set of

more than 600 endgame positions, included some tricky ones.

For people interested to redo the test or doing additional tests

please pull branch tb_dbg from https://github.com/mcostalba/Stockfish repo.

bench: 8450534 (bench unaffected because syzygy is not exercized during bench)

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