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 JA | 2/2 | +2 | 2 games |
| Cadie 2.1 JA | 1.5/2 | +1 | 2 games |
| Critter 1.6a | 1.5/2 | +1 | 2 games |
| Kociolek 2.1 JA | 1.5/2 | +1 | 2 games |
| Monolith 3 | 1.5/2 | +1 | 2 games |
| Jet 1.2 | 0.5/2 | -1 | 2 games |
| Maelstrom 3.3.0 | 1/1 | +1 | 1 games |
| Solo 2.2.0 JA | 1/1 | +1 | 1 games |
| Invictus r391 JA | 1/1 | +1 | 1 games |
| Flounder 0.5.0.2 | 1/1 | +1 | 1 games |
| Beef 0.3.6 JA | 1/1 | +1 | 1 games |
| Fizbo 2 JA | 1/1 | +1 | 1 games |
| DanaSah 9.1 | 1/1 | +1 | 1 games |
| Defenchess 2.3 JA | 0.5/1 | +0 | 1 games |
| Vajolet2 3.1.0 | 0.5/1 | +0 | 1 games |
| Odonata 1.1.0 | 0.5/1 | +0 | 1 games |
| Svart 6 JA | 0.5/1 | +0 | 1 games |
| Frozenight 7.0.0 JA | 0.5/1 | +0 | 1 games |
| Drofa 4.1.1 JA | 0.5/1 | +0 | 1 games |
| Bit-Genie 9.24 JA | 0.5/1 | +0 | 1 games |
| Myrddin 0.96 JA | 0.5/1 | +0 | 1 games |
Jim Ablett compiles:

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