Arasan 15.0

[jdart]

Arasan 15.0 is available from http://www.arasanchess.org.

Changes in Arasan 15.0:
1) Increase static null pruning threshold at low depths.
2) Scoring fixes/improvements: king cover, potential passed pawns,
bad bishop.
3) Fix code that tracks node count per ply 0 move, for move ordering.
4) Changes to LMR reduction amounts and ply 0 reduction threshold.
5) Avoid null move if hash table info indicates it would fail to
generate cutoff.
6) Losing checks are no longer extended, in any case. Threat extension
is now done differently, similar to Stockfish.
7) Re-work of SMP code to increase thread usage by supporting the
"helpful master" algorithm.
8) Fix a bug in communicating with the Fritz interface, specifically
the "process testsuite" command.
9) Fix UCI and console score output so upperbound & lowerbound status
displayed when appropriate.
10) Fix setting Strength option from native GUI.
11) Some GNU Makefile fixes for MingW support. clang is also supported
now.

This version is clearly stronger than 14.3 in my testing. About 25 ELO points on my arbitrary rating scale. Maybe more for CEGT etc where the ratings tend to be higher.

An updated version of the Arasan test suite is also available. See http://www.arasanchess.org/testsuite.shtml.