Evaluations of the opening book, which was/were published on : https://www.patreon.com/analysis4chess : is below.
Short summary:
Elo-based large-scale comparison was considered (yet still impractical due to resource constraints, as stated in 2023). Since then, the book has been developed heuristically.
In 2025, focus shifted toward improving the book’s absolute strength, with continued but more controlled expansion and pruning.
For more meaningful comparisons, from January 2026, additional evaluations are carried out based on accuracy and CPL (centipawn loss), measured on source sequences using fixed-depth engine analysis.
The source sequences of the current Alpha 56 version (June 2026) show ~98.64% accuracy under Stockfish 17.1 (NNUE, BMI2/AVX2) fixed 32-ply depth testing.
Exact details related to the evaluation of book version Alpha 56:
METADATA
- Date: 2026-06-05 07:21:02
- Engine: Stockfish 17.1 NNUE BMI2
- Engine evaluation depth: 32 plies
- Threads: 8
DATASET SIZE
- Total sequences: 129,198
- Total moves in the sequences: 2,377,183
SEQUENCE LENGTH PROFILE
- Mean sequence length: 18.40 plies
- Median sequence length: 16.00 plies
- Min / P10 / Median / P90 / Max: 3 / 7 / 16.00 / 40 / 40 plies
- Sequences reaching >= 8 plies: 87.58%
- Sequences reaching >=12 plies: 80.58%
- Sequences reaching >=16 plies: 60.50%
- Sequences reaching >=20 plies: 25.44%
- Sequences reaching >=30 plies: 16.15%
QUALITY METRICS (accuracy + CPL)
- Combined accuracy: 98.64%
- Mean CPL: 4.73 cp
- Median CPL: 1.00 cp
- P90 CPL: 14.00 cp
WHITE ERROR RATES
- Accuracy <95 : 9.24%
- Accuracy <90 : 2.84%
- Accuracy <80 : 0.16%
- Accuracy <70 : 0.03%
BLACK ERROR RATES
- Accuracy <95 : 8.55%
- Accuracy <90 : 1.72%
- Accuracy <80 : 0.14%
- Accuracy <70 : 0.03%
COMBINED ERROR RATES
- Accuracy <95 : 8.90%
- Accuracy <90 : 2.29%
- Accuracy <80 : 0.15%
- Accuracy <70 : 0.03%
WHITE VS BLACK (accuracy)
- White: 98.57%
- Black: 98.71%
- Edge: Black +0.14%
CONSISTENCY
- Sigma (standard deviation): 2.7356
- IQR (interquartile range): 1.4503
2026. June 06.