Arasan 21.3

[jdart]

Arasan 21.3 is available from:

https://www.arasanchess.org

Changes in Arasan 21.3:

1) Fix possible array overflow in search.
2) Clean up draw code; fix bug where 2-fold repetition at root caused
draw to be signalled.
3) When a hash hit occurs in the qsearch, do a more correct check
that the hash move meets conditiions for the current phase of
the search, before using it. Also: remove pruning for hash
moves in qsearch.
4) Remove eval test before doing checks in qsearch.
5) Simplify book selection logic. Add an additional option for
controlling how important explicit book weights are.
6) Fix bounds overflow in king proximity table.
7) Remove some scoring parameters that were tuned to zero or near-zero.
8) Reset controller stop flag before search. Fixes issue #21.
9) For pruning decisions, use modified depth but not the same as
LMR depth (idea from Laser). Allow pruning of non-root PV nodes.
10) Store history scores on all moves including pruned ones.
11) Use counter move and follow-up history for pruning like Stockfish.
12) Omit futility pruning for moves with good history.
13) Fixes/simplifications to ProbCut code. Reduce ProbCut margin.
14) Adjust SEE pruning margin for non-quiet moves.
15) Don't do quiet move pruning if side to move has no pieces.
16) Assorted code cleanup. Add unit tests for search.

I am estimating +25 to 30 ELO for this version over Arasan 21.2 on a CEGT/CCRL scale.

--Jon

[Damir]

Thanks Jon. You are doing an amazing work so far, and continously keep on improving your engine.

[Guenther]

Arasan 21.3 is available from:

https://www.arasanchess.org

--Jon

Thanks Jon!

[Graham Banks]

Arasan 21.3 is available from:

https://www.arasanchess.org

Thanks.

[Dann Corbit]

Thanks for the new toy.

About the current Arasan 20 test set from your site...

I have this comment c0: 'Gaw Paw Sicilian: http://rybkaforum.net/cgi-bin/rybkaforu ... ?tid=18253'
for: rnb1kb1r/pp1p1ppp/1q2p3/8/3NP1n1/2N1B3/PPP2PPP/R2QKB1R w KQkq -

And you are missing a check sign on the key move for: r3nrk1/1pqbbppp/p2pp3/2n1P3/5P2/2NBBNQ1/PPP3PP/R4RK1 w - -
since 'Bxh7' should be 'Bxh7+'.

[jdart]

About the current Arasan 20 test set from your site...

Thanks for the fixes, will update it.

--Jon