Arasan 12.2 released

[jdart]

Arasan 12.2 is available from http://www.arasanchess.org. This is the same version that played in the recent ACCA tournament, plus a few very minor tweaks.

Changes in Arasan 12.2:
1) Somewhat complex trade scoring has been removed - in favor of just
adjusting piece values.
2) More aggressive futility pruning, margin is adjused at 1/2 ply increments.
3) Changes to extension/pruning logic. LMR now done after futility. Extra
LMR is done at high depths/move counts.
4) King safety scoring changed - open files are now scored separately,
score is based on opposing Rook + Queen count.
5) Bishop pair score reduced (but increases in endgame).
6) Changes to pawn scoring: outside pawn & doubled pawn scores reduced.
7) Outside pawn calc is done via a table, like Crafty does.
8) Penalty for own pieces ahead of passer; somewhat reduced bonus for rook
behind passer.
9) EGTB values are no longer hashed (seemed to cause problems).
10) Minor GUI fix: remove trailing junk after game description.

[Graham Banks]

Arasan 12.2 is available from http://www.arasanchess.org. This is the same version that played in the recent ACCA tournament, plus a few very minor tweaks

Thanks Jon.

[beachknight]

Thanks Jon.

Any info on rating gain?

[jdart]

Based on my testing, I think this version is stronger than 11.7 or 12.1 (which are fairly close to =). Last time I tested it was scoring about 55% against 11.7, but that wasn't exactly this version.

[michiguel]

Arasan 12.2 is available from http://www.arasanchess.org. This is the same version that played in the recent ACCA tournament, plus a few very minor tweaks.

Changes in Arasan 12.2:
1) Somewhat complex trade scoring has been removed - in favor of just
adjusting piece values.
2) More aggressive futility pruning, margin is adjused at 1/2 ply increments.
3) Changes to extension/pruning logic. LMR now done after futility. Extra
LMR is done at high depths/move counts.
4) King safety scoring changed - open files are now scored separately,
score is based on opposing Rook + Queen count.
5) Bishop pair score reduced (but increases in endgame).
6) Changes to pawn scoring: outside pawn & doubled pawn scores reduced.
7) Outside pawn calc is done via a table, like Crafty does.
8) Penalty for own pieces ahead of passer; somewhat reduced bonus for rook
behind passer.
9) EGTB values are no longer hashed (seemed to cause problems).

I am curious, what were exactly the symptoms?

Miguel

10) Minor GUI fix: remove trailing junk after game description.

[beachknight]

Based on my testing, I think this version is stronger than 11.7 or 12.1 (which are fairly close to =). Last time I tested it was scoring about 55% against 11.7, but that wasn't exactly this version.

Thank you. For rating calculation, I might combine the games of 12.1
and 12.2 since they have not played sufficient games.

[jdart]

Thank you. For rating calculation, I might combine the games of 12.1
and 12.2 since they have not played sufficient games.

Not sure that makes sense, since what I am saying is, I don't think they are the same strength.

[jdart]

I am curious, what were exactly the symptoms?

If you are referring to the EGTB issue - online, it lost a few won or drawn games in TB endings, returning an incorrect score. I only saw this on Windows (lately the machine on the chess servers is usually Linux). So I have not analyzed it down to a root cause exactly, but after removing the caching I didn't see this issue.

[Jouni]

As UCI engine under Fritz10 Arasan 12.2 (as older versions) crash always fast, any idea why? I have all files even arasan.rc in engine directory.
I don't know other UCI engine with so serious problem, here W7 error info (in finnish):

Ongelmatapahtuman nimi: APPCRASH
Sovelluksen nimi: arasanx-64.exe
Sovelluksen versio: 0.0.0.0
Sovelluksen aikaleima: 4cdb7092
Vikamoduulin nimi: arasanx-64.exe
Vikamoduulin versio: 0.0.0.0
Vikamoduulin aikaleima: 4cdb7092
Poikkeuskoodi: c0000005
Poikkeuksen poikkeama: 00000000000637cb
Käyttöjärjestelmän versio: 6.1.7600.2.0.0.768.3
Aluekohtaisten asetusten tunnus: 1035
Lisätietoja 1: 74b8
Lisätietoja 2: 74b89907bc31608010fdaa475abffff2
Lisätietoja 3: 14aa
Lisätietoja 4: 14aae977ffaa1d105bf867f43c8f1a75

Jouni

[jdart]

I don't know - I don't have Fritz and don't test in that environment.

It works in Arena + Shredder UI.