Petrel 4.1 JA - new version chess engine


Petrel, about the engine:
Petrel 4.0 JA competed in Group B during the 9/2026 season, finishing third and earning promotion to the top-tier Group A. Next, it will aim for a spot in the Top 64 in the 10/2026 season. It’ll be interesting to see how the new version performs.

Author: Aleks Peshkov  Rating Chess Engines Diary CEDR=3545

Petrel what's new?
Stronger net (360SB, WDL 0.0 -> 0.2)
NNUE horizontal mirroring
NNUE fused updates
TT 2-tier buckets, using TT in QS
reusing static eval from TT
small search and move ordering adjustments

Petrel 3.5 JA vs other engines:

Maestro 1.2.1 JA2/2+22 games
Cadie 2.1 JA1.5/2+12 games
Critter 1.6a1.5/2+12 games
Kociolek 2.1 JA1.5/2+12 games
Monolith 31.5/2+12 games
Jet 1.20.5/2-12 games
Maelstrom 3.3.01/1+11 games
Solo 2.2.0 JA1/1+11 games
Invictus r391 JA1/1+11 games
Flounder 0.5.0.21/1+11 games
Beef 0.3.6 JA1/1+11 games
Fizbo 2 JA1/1+11 games
DanaSah 9.11/1+11 games
Defenchess 2.3 JA0.5/1+01 games
Vajolet2 3.1.00.5/1+01 games
Odonata 1.1.00.5/1+01 games
Svart 6 JA0.5/1+01 games
Frozenight 7.0.0 JA0.5/1+01 games
Drofa 4.1.1 JA0.5/1+01 games
Bit-Genie 9.24 JA0.5/1+01 games
Myrddin 0.96 JA0.5/1+01 games


Jim Ablett compiles:

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