Author:Dan Kelsey
v.6.0.0:
This major release of Calvin aims to achieve two significant milestones:
Reaching an elo rating of 3600 (CCRL Blitz).
Establishing Calvin as the strongest Java chess engine in the world.
Calvin 6.0.0 does not feature a new neural network or any improvements to the evaluation function. Instead, all the strength gains were found in search - the most notable being singular extensions.
Tests against the previous release suggest a strength increase of around 93 elo LTC / 67 elo STC:
LTC (40+0.4): Elo | 93.39 +- 5.84
STC (8+0.08): Elo | 67.19 +- 6.13
Those improvements give Calvin 6.0.0 an estimated rating of 3600 CCRL Blitz.
The strongest Java chess engine
I ran some tests againt Serendipity, the current top Java engine. The results show that Calvin is now significantly stronger:
LTC (40+0.4): Elo | 51.79 +- 14.33
STC (8+0.08): Elo | 71.19 +- 18.94
Therefore Calvin is (as far as I am aware) the new top Java engine in the world!
🔍 Search Improvements
Singular extensions (#115)
Double extensions (#305)
Negative extensions (#306)
Double negative extensions (#310)
Fix corrhist updates (#286 / #287)
Use history score in PVS SEE pruning (#284)
Fix cutnode usage (#309)
Cutnode LMR (#310)
Futility LMR (#304)
Do IIR when TT depth is shallow (#312)
Write to TT in Q-search stand-pat beta cutoff (#298)
Only skip SEE pruning for good noisies (#297)
SPSA tune (#301)
How to run
To run the jar file, you will need to enable the Vector API package which Calvin uses for SIMD, via this command:
java --add-modules jdk.incubator.vector -jar path/to/calvin-chess-engine-6.0.0.jar
For CCRL testers who use ChessGUI, please also download the calvin-wrapper.jar file and place it in the same folder as the calvin jar. When loading Calvin in ChessGUI, pass this file instead of the engine jar. This wrapper allows you to run Calvin without passing in the required JVM args (which ChessGUI does not support).
Jim Ablett compiles:
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