Arasan 18.1

[jdart]

Arasan 18.1 is available from http://www.arasanchess.org.

Changes in Arasan 18.1:

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 1) Less aggressive LMR and LMP.
 2) More parameters are made tunable.
 3) Tuning code revised to support MMTO and Texel methods and params
    adjusted via tuning.
 4) Bug fixes in potential passer scoring.
 5) Score Q + minor vs Q as draw.
 6) In a multi-threaded search, maintain a move index in the move generator and pass it to the threads, for better/more consistent move order-based pruning & reductions.
 7) Increase max split depth.
 8) Change how passed pawn blockers are scored and tune penalities.
 9) Fix scoring for two rooks on the 7th rank.
10) After reduced depth search fails high, don't re-search with narrow
    window and no reduction, unless reduction was > 1 ply.
11) Modify formula for time extension when failing low.
12) Bug fix: do not ponder after draw claim in Winboard mode.
13) Increase SEE pruning depth but disable if alpha is a mate score.

This is stronger than 18.0 in my testing (+10 elo or so, maybe +15 on a CCRL/CEGT rating scale). I have not done a rating test for multi-core usage, but changes 6 and 7 should improve performance there.

[Graham Banks]

Thanks.

[Frank Quisinsky]

Hi Jon,

at first, thanks for your new version and your information in detail.

at second ...
Looking in my own ratings in case of Arasan because I can see the small improvements more exactly with all the opponents I am using.

Puh ...
Over 7.150 games in a short time on my i7 4th generation Systems for my not very old Rating List.

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71 Arasan 18.0 POP x64              : 2725.7   10.6   1035.0    2750   37.6%
74 Arasan 17.5 POP x64              : 2718.9   11.9    849.5    2000   42.5%
82 Arasan 17.4 POP x64              : 2693.9   11.0   1048.0    2400   43.7%

I added the new version on my ToDo list.

Best
Frank

[Werner]

Hi Jon,
thanks for the new version:
439 Arasan 17.5 x64 1CPU 2691 13 13 1505
455 Arasan 18.0 x64 1CPU 2684 16 16 1200

I hope 18.1 will catch 17.5 in our list

[cdani]

Thanks for this version.

Two things that I will try in Andscacs

5) Score Q + minor vs Q as draw.
9) ... scoring for two rooks on the 7th rank.

[MikeB]

Thanks Jonathan. Always good to see an "oldie" being constantly updated. Just out of curiosity - what year was Arasan first released? It had to be more than 20 years ago.

[jdart]

First release was in 1994 (Windows only, integrated GUI + engine).

It was released as a separate Winboard-compatible engine in 1996.

--Jon

[Jamal Bubker]

Thank you Jon for this new release

[Jesse Gersenson]

First release was in 1994 (Windows only, integrated GUI + engine).

Ah, my first and only true love of computer chess. It runs under wine, some of the features don't work - but it plays a game of chess.

[Sylwy]

http://talkchess.com/forum/viewtopic.ph ... 40&t=50060