If you are testing Lozza please use the latest release and not the coalface from the repo; which is usually broken in some way; thanks.

Lozza

A UCI Javascript chess engine using a small NNUE for evaluation. Try her here:-

https://op12no2.github.io/lozza-ui

Lozza was primarily created for use in browsers, but can also be used with traditional chess UIs via Node.js and on pretty-much any platform (see below). Note however that Lozza is relatively slow compared to compiled engines of a similar design, which also makes her relatively weak.

Basic use in a browser

All you need is lozza.js from the latest release.

Here is a little example to do a 10 ply search:-

var lozza = new Worker('lozza.js');

lozza.onmessage = function (e) {
  $('#dump').append(e.data);             //assuming jquery and a div called #dump
                                         //parse messages from here as required
};

lozza.postMessage('uci');                // lozza uses the uci communication protocol
lozza.postMessage('ucinewgame');         // reset tt
lozza.postMessage('position startpos');
lozza.postMessage('go depth 10');        // 10 ply search

Try this example here:-

https://op12no2.github.io/lozza-ui/ex.htm

Please note that Lozza's code is folded using {{{ and }}} (emacs convention) and most easily read using an editor with a folding capability.

More examples

A sister repo has more browser-based examples for playing and analysing etc. with Lozza.

https://github.com/op12no2/lozza-ui

You can try them here:-

https://op12no2.github.io/lozza-ui

Play Lozza offline in chess user interfaces

Lozza can be used in popular chesss user interfaces like Banksia, Winboard, Arena and CuteChess via Node.js. Download the latest release and then follow the instructions in the readme.txt file. Any platform that supports Node.js can be targetted.

https://github.com/op12no2/lozza/releases

Fire up Lozza from the command line

To type UCI commands into Lozza, start Node.js with lozza.js or lozza as the parameter and then enter commands. For example:-

> node lozza
ucinewgame
position startpos
eval
go depth 10
quit

Commands can also be given on invocation, for example:-

> node lozza ucinewgame bench "position startpos" board "go movetime 100" quit

Alternatives to Node.js are Bun and Deno.

Commands specific to Lozza

eval displays the current evaluation of the board.

board displays the board as a FEN string.

bench does a cumulative node count while searching a list of FENs, displaying the total and the time it took. It's particularly useful when checking that changes that should not affect searching have in fact not affected searching.

et tests the UE part of NNUE.

pt performs a sequence of PERFT tests.

net displays network properties.

Creating your own nets

Lozza's net was trained using a datagen.js -> filter.js -> trainer.js Javascript pipeline. Contact me if you are interested in training a different net for your project; it's very straightforward.

Acknowledgements

https://www.chessprogramming.org/Main_Page - Chess programming wiki.

https://computerchess.org.uk/ccrl/4040 - CCRL rating list.

https://www.wbec-ridderkerk.nl/html/UCIProtocol.html - UCI protocol.

https://discord.gg/uM8J3x46 - Engine Programming Discord - thanks for the help with NNUE/datagen concepts.

https://talkchess.com - Talkchess forums.

op12no2 / lozza

readme