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Caissa 1.7 - released.

The Chess Goddess has visited the humble thresholds of Finally.

Source: GitHub

Caissa - the legendary Chess Goddess, who was once illustrated several hundred years ago by Domenico Maria Fratta. And she looked like this:

Source: Wikipedia

Undoubtedly, both portrayed Goddesses have their own charm, but I more often glance into the steeple of the former from the top of the page ;)

Caissa is a strong and free open source chess engine licensed from MIT. Caissa is a relatively young engine playing at around 3400 Elo. It owes its not inconsiderable strength to its author Mr. Michal Witanowski, who regularly updates his creation with more and more advanced techniques.

Source: MCERL (ongoing)

Here are the changes introduced in the latest Caissa 1.7



  • Increase neural net accumulator size from 1024 to 1536

  • New neural network trained on 750M positions

  • Refactor move generation

  • Refactor counter move history

  • Skipping quiet moves generation when late move prunning triggers

  • Tweaking Late Move Reductions

  • Tweaking Singular Extensions

  • Introduce Counter Moves

  • Staged generation of Killer and Counter Moves

  • Fix bug in Static Exchange Evaluation

  • Store only 1 move in Transposition Table entry (instead of 3)

  • Optimize neural net's last layer evaluation

  • Don't report PV lines in first 5ms of search

  • Prune only really bad captures in QSearch

  • Adding some KQvKRP endgame knowledge

  • Introduced 'hashfull' UCI reporting

  • Tweaking various parameters


Source: GitHub

Unfortunately, although Caissa is an open-source engine, its code is oriented toward the Windows environment. After many attempts to adapt the code to compile for Linux and Mac, a binary was created that does not work.

As a result, I got in touch with the author of this chess engine and... I received good news!

Mr. Michal Witanowski is planning to deal with support for ARM64, so on Macs with Apple Silicon processor and probably Linux, Caissa should work :)

In my experience, if something works on arm64, there are usually no major problems with porting to other architectures, such as for Linux x64.

Well, I hold Mr. Michal Witanowski to his word and look forward to the Caissa source code allowing Caissa to compile and work properly for Linux and Mac.

Before I encourage you to download the Caissa chess engine, I invite you to see a sample of Caissa 1.7's abilities*.

The following position was created after both engines selected a quiet continuation in the Spanish opening.

White plays Caissa 1.7, black plays Counter 5.0.

Caissa gained a clear strategic advantage: Bishop Counter 5.0 is cut off from the main events on the chessboard, Black's king has not managed to exercise his castling right.

Are we sure it will be a peaceful continuation, a peaceful game?

Nothing of the sort.

Fen: r3k2r/bpp3p1/2p1Ppn1/p1P2bN1/1P2N2p/P6P/4RPP1/2BR2K1 w - - 0 21


Caissa sacrifices her Knight to wedge herself as close as possible to the black King's position.

Fen: r3k2r/bppR2p1/2p1Ppn1/p1P2bN1/1P2N2p/P6P/4RPP1/2B3K1 b - - 1 21

Despite their material advantage, Counter 5.0 figures are silent and serve as extras, not participants in events.

Fen: r3k2r/bppR2p1/2p1P1n1/p1P2bB1/1P2N2p/P6P/4RPP1/6K1 b - - 0 22

Using the active position of all her figures and pawns, Caissa transforms her initiative and advantage into quantifiable material gains. Counter 5.0 resisted, but was unable to save the game.

Fen: r3kQ2/1p6/2p5/2b3R1/1p2R2p/P6P/5PP1/6K1 b - - 0 29

Download ZIP • 4KB

Feel free to download Caissa 1.7 for Windows.

Windows x64 – Compiled by Darius

Download 7Z • 1.93MB


In the Files area you will find free chess engines for download.


* Diagrams generated in Dragon 3 by Komodo Chess (Fritz 18 GUI).


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