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Chess engine: Expositor 2BR17


Expositor is a UCI-conforming chess engine for AMD64 / Intel 64 systems.
Author: Kade  Rating CEDR 15'+10"=3048Rating CEDR 3'+3"=2994

v.2BR17:
Overview
This release features two major improvements:

Search Tuning Many of the constants in Expositor's search have now been tuned with a variation of simultaneous perturbation stochastic approximation (SPSA). Along with internal iterative reductions, this has increased the strength by approximately 100 Elo against 2WN29 in self-play.

Internal Tablebases Expositor now has an internal 3-man tablebase and I'm working on an optional 4-man tablebase. This will not increase her strength, since her endgame heuristics are sufficient for 3- and 4-man endgames (besides some KBN v K positions), but I wanted a break from work on HCE bootstrapping and thought it would be fun.

The complete list of changes made in this release is below.

Fixes
fixed error where spurious moves could be printed at the end of the principal variation (PV)
fixed error in Linux build script that caused the script to fail when building commits with commit dates in August through December

Improvements
search constants have been tuned with a modified form of SPSA
added internal iterative reductions
transposition table entries are now prefetched
added internal 3-man tablebase
threads now clear their own context and statistics in parallel when a search begins
the PGN parser can now handle moves written without a space after the move number (e.g. 1.e4)

Time Control
target time adjustments based on PV stability now depend on the depth at which the PV changes
searches are now less likely to stop immediately after the PV changes

Miscellaneous
scores taper to half their nominal value rather than to zero as the 50-move horizon approaches
made slight improvements to the efficiency of static exchange analysis
made various small simplifications in the codebase
added various developer tools

Individual statistics: Expositor 2WQ23 - 72 games (+ 31,= 14,- 27), 52.8 % (15'+10")
Jackychess 0.9.14             :   1 (+  1,=  0,-  0), 100.0 %
Kouri 1.15                    :   1 (+  1,=  0,-  0), 100.0 %
Sapeli 2.0                    :   1 (+  1,=  0,-  0), 100.0 %
Rustic Alpha 3.0.0            :   1 (+  1,=  0,-  0), 100.0 %
Iathena 2020-12-19            :   1 (+  1,=  0,-  0), 100.0 %
FracTal 1.0                   :   1 (+  1,=  0,-  0), 100.0 %
Chareth 0.1.0                 :   1 (+  1,=  0,-  0), 100.0 %
Quokka 2.1                    :   1 (+  1,=  0,-  0), 100.0 %
Monochrome r203               :   1 (+  1,=  0,-  0), 100.0 %
Stockfish 14.1                :   2 (+  0,=  1,-  1), 25.0 %
Pulse 1.7.3                   :   1 (+  1,=  0,-  0), 100.0 %
SugaR AI 2.50                 :   2 (+  0,=  1,-  1), 25.0 %
Fisherov 0.98i                :   2 (+  0,=  0,-  2),  0.0 %
BLANK 1.3.0                   :   1 (+  1,=  0,-  0), 100.0 %
Lynx 0.9.0                    :   1 (+  1,=  0,-  0), 100.0 %
MisterQueen                   :   1 (+  1,=  0,-  0), 100.0 %
Lc0 0.28.2                    :   4 (+  0,=  1,-  3), 12.5 %
Weiawaga 4.0                  :   1 (+  1,=  0,-  0), 100.0 %
Popochin 4.3                  :   1 (+  0,=  1,-  0), 50.0 %
Prophet 4.1                   :   1 (+  1,=  0,-  0), 100.0 %
Anka 0.6.3                    :   1 (+  1,=  0,-  0), 100.0 %
Eman 7.80                     :   2 (+  0,=  0,-  2),  0.0 %
Dragon 2.6.1                  :   2 (+  0,=  1,-  1), 25.0 %
ClassicAra 0.9.9              :   5 (+  2,=  3,-  0), 70.0 %
SlowChess 2.83                :   2 (+  0,=  0,-  2),  0.0 %
Leorik 1.0                    :   1 (+  1,=  0,-  0), 100.0 %
Fatalii 0.1.0                 :   1 (+  1,=  0,-  0), 100.0 %
Tantabus 2.0.0                :   1 (+  1,=  0,-  0), 100.0 %
Koivisto 7.14 Ipman           :   2 (+  0,=  1,-  1), 25.0 %
Journeyman 1.0                :   1 (+  1,=  0,-  0), 100.0 %
Eggnog 3.0                    :   1 (+  1,=  0,-  0), 100.0 %
Corchess 250222               :   2 (+  0,=  0,-  2),  0.0 %
Stockfish 010322              :   2 (+  0,=  1,-  1), 25.0 %
Frozenight 1.0.0              :   2 (+  2,=  0,-  0), 100.0 %
Rebel 14.2                    :   2 (+  0,=  0,-  2),  0.0 %
Stockfish 250222 Ivec         :   2 (+  0,=  0,-  2),  0.0 %
Dumb 1.9                      :   2 (+  2,=  0,-  0), 100.0 %
BrainLearn 16                 :   2 (+  0,=  1,-  1), 25.0 %
Lozza 2.2                     :   1 (+  1,=  0,-  0), 100.0 %
Little Goliath 3.15.4         :   1 (+  0,=  1,-  0), 50.0 %
Frozenight 2.0.0              :   1 (+  1,=  0,-  0), 100.0 %
Princhess 0.7.0               :   1 (+  1,=  0,-  0), 100.0 %
Walleye 1.6.0                 :   1 (+  1,=  0,-  0), 100.0 %
CorChess 010422               :   2 (+  0,=  0,-  2),  0.0 %
ProteusSF 006                 :   2 (+  0,=  1,-  1), 25.0 %
Stockfish 010422 Ivec         :   2 (+  0,=  0,-  2),  0.0 %
Kayra 1.3                     :   2 (+  0,=  1,-  1), 25.0 %


github:https://github.com/expo-dev/expositor/releases/tag/2BR17


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