Arasan 16.0

[jdart]

Arasan 16.0 is available from http://www.arasanchess.org.

Changes in Arasan 16.0:
1) Improvements to multi-core and multi-processor performance: limit
global memory usage, do dynamic adjustment of split depth.
2) Change book format, book weights are 0..100 not 0..10 now. New
larger opening book is included with Arasan binaries.
3) Book selectivity logic changed (again).
4) Fix bug in 50-move draw detection.
5) Move sorting no longer uses node counts; now an initial sort is
done by move score, then subsequently PV moves are moved to the front
each iteration, keeping other moves in the same order.
6) Check extensions are more limited now. Overall limit on extensions
at high ply counts from root is removed.
7) Search time can be extended more in case of fail-low or resolving a
fail-high.
8) Aspiration window changes. Fix bug that can cause array overflow in
aspiration window code.
9) Somewhat experimental self-play code added for testing (not enabled
in release builds by default).
10) Numerous adjustments to evaluation weights.
11) Score pawnless KRB vs KR and KRN vs KR as draws.
12) Bug fix: allow resignation when in fixed depth search and depth<=1.
13) Fix bug in handling of fail_high_root flag.
14) Convert to conditional variables for thread synchronizaton on Linux
+ Mac (fixes Mac OS problem where semaphores may not be cleaned up
on exit).
15) Fix stack size for threads on Mac OS (avoids bus error crash in deep
searches).

This is basically the same version that played in the recent WCRCC tournament, with a few opening book additions and some fixes for Mac OS (the last two items on the change list).

Note that the opening book format has changed for this version, so books used with version 15.6 and earlier do not work with 16.0.

Re playing strength, this version is measurably stronger than 15.6 but IMO there is not a dramatic difference at least when run single-threaded. Multi-threaded performance should be quite a bit better than 15.6, but I don't have data to quantify that in terms of ELO.

Source code is available on the download page and also on Github (https://github.com/jdart1/arasan-chess).

--Jon