Chess engine: Alexandria
Author: PGG106 Rating Chess Engines Diary CEDR=3720
Alexandria 8.1.0 what's new?
Search Changes
Improved LMR.
Reintroduced draw score randomization.
Introduced QS failfirm standpat.
Introduced a simplified and more efficient stack-based Unmake.
Introduced GHI prevention.
Added History pruning.
Improved NMP efficiency.
Eval Changes
Major NNUE simplification, eliminating most of the UE work.
Mijor speedup in NNUE indexing.
Switched to material based scaled instead of phase based scaling.
New net trained with WDL skipping.
Misc stuff
Vastly improved SF inspired TM.
Improved code layout.
Improved SEE with pinned pieces detection.
NNUE binary is now Mmap'd for improved performance on machines with several concurrent engine processes.
Minor improvement in qsearch efficiency obtained by reworking the branching conditions.
Alexandria 8.1.0 - progression test:
LTC Progression test
Elo | 19.84 +- 3.15 (95%)
Conf | 60.0+0.60s Threads=1 Hash=64MB
Games | N: 10012 W: 2952 L: 2381 D: 4679
Penta | [4, 784, 2870, 1333, 15]
Alexandria 8.0.0 - results:
| Stockfish 17.1 | 19/39 | -1 | 39 Games |
| PlentyChess 6.0.5 JA | 14/28 | +0 | 28 Games |
| Berserk 20250307b | 12/22 | +2 | 22 Games |
| Dragon 3.3 | 10.5/22 | -1 | 22 Games |
| Berserk 20250606 | 9.5/20 | -1 | 20 Games |
| Yuliana 7.0 | 9.5/20 | -1 | 20 Games |
| RubiChess 20250606 JA | 9/18 | +0 | 18 Games |
| Cool Iris 14 | 8/18 | -2 | 18 Games |
| Lc0 0.31.2 | 8/14 | +2 | 14 Games |
| Kookaburra 3.10 | 7/14 | +0 | 14 Games |
| Cool Iris v19 | 7/14 | +0 | 14 Games |
| DarkSeid 6.2 EE | 6/14 | -2 | 14 Games |
| Obsidian dev-16.14 | 6.5/13 | +0 | 13 Games |
| CalvinChess 6.0.0 JA | 9/12 | +6 | 12 Games |
| Stormphrax 6.0.0 | 7/12 | +2 | 12 Games |
| Booot 7.4 | 6/12 | +0 | 12 Games |
| Green Way | 5.5/12 | -1 | 12 Games |
| Contact 12 | 5/12 | -2 | 12 Games |
| Mayhem 8.8 JA | 10/10 | +10 | 10 Games |
| Uralochka 3.42 dev13 | 7/10 | +4 | 10 Games |
| Pawnocchio 1.7.2 | 7/10 | +4 | 10 Games |
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