Caissa 2.0 - new version strong chess engine

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Caissa - UCI chess engine,  Author: Michał Witanowski
Rating Chess Engines Diary CEDR=3792

Caissa - what's new?

Caissa 2.0
This release switches the evaluation to a multilayer neural network and brings a new AVX-512 Ice Lake build, much better play at ultra-short time controls, and minor fixes.

Playing Strength
LTC, 60+0.6, UHO book:
ELO    40.41 +- 4.85 (95%)
CONF   60.0+0.60s Threads=1 Hash=128MB
GAMES  N: 5000 W: 1480 L: 901 D: 2619
PENTA  [5, 357, 1211, 908, 19]
https://furybench.com/test/7443/

STC, 10+0.1, UHO book:
ELO    29.15 +- 4.59 (95%)
CONF   10.0+0.10s Threads=1 Hash=16MB
GAMES  N: 6284 W: 1814 L: 1288 D: 3182
PENTA  [25, 550, 1478, 1052, 37]
https://furybench.com/test/7442/

STC, 10+0.1, DFRC UHO book:
ELO    28.69 +- 10.70 (95%)
CONF   10.0+0.10s Threads=1 Hash=16MB
GAMES  N: 1396 W: 398 L: 283 D: 715
PENTA  [13, 126, 314, 223, 22]
https://furybench.com/test/7445/

Changes
Evaluation
New multilayer network (32×768 → 1536) × 2 → 16 → 32 → 1:
The first layer is wider than before (1536 neurons per side, up from 1024).
Pairwise activation.
Two small hidden layers, with 8 output subnetworks selected by piece count.
Sparse inference skips the zero activations.
The network was trained from scratch for 312B positions, and its last layer was then tuned with SPSA.
Search & Time Management
MoveOverhead now actually reserves time. That's worth +28 to +63 Elo at time controls from 1+0 down to 0.1+0.001.
Tighter singular extension margin on exact TT bounds.
TT entries from earlier searches are always replaced.
Performance
New avx512icl build: +4.2% nps on Zen 4.
Fixed pext/pdep falling back to software emulation on Linux builds.
GCC codegen flags: +0.5% to +2.5% nps.
Bug Fixes
FEN parsing fixes (#25): X-FEN castling rights with several rooks, en passant validation, and rejection of malformed FENs.
hashfull reported 0 after 64 searches.
Tools
The CUDA trainer supports the multilayer net and gained an input factorizer, a cosine LR schedule and checkpoint/resume.
New utils permuteNet tool.
The legacy CPU trainer was removed.

Caissa engine's best results in our tests:




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