Lozza is a Javascript UCI chess engine that can be easily be deployed using a web worker. It can also be used with traditional chess user interfaces via Node.
Other then the network weights, the source is hand-coded and easily tweakable.
This can be done using a batch file and full path names are recommended.
"C:\Program Files\nodejs\node.exe "c:\path\to\lozza.js"
Then use the batch file to load Lozza into the user interface. Email me if you get any problems op12no2@gmail.com.
All you need is lozza.js from the latest release.
Here is a little example to do a 10 ply search:-
const lozza = new Worker('lozza.js');
const ucioutput = document.getElementById('ucioutput');
lozza.onmessage = function(e) {
ucioutput.textContent += e.data + '\n'; // Lozza reponds with text as per UCI
};
lozza.postMessage('uci');
lozza.postMessage('ucinewgame');
lozza.postMessage('position startpos');
lozza.postMessage('go depth 10');Try this example here:-
A sister repo has more browser-based examples for playing and analysing with Lozza.
Lozza's net was booted from quiet_labeled.epd and lichess-big3-resolved.epd, then iteratively improved through six generations of self play and training; initially using a diy trainer and more recently with bullet. Currently it's a simple quantised 768->(256*2)->1 squared ReLU architecture, trained on about 600M positions. It's embeded into lozza.js as a single line of code towards the end of the file.
Lozza does not support the stop command or multi-threading.
You can either edit lozza.js directly or clone/download the repo and edit the individual files in src. There is a little script bin/build to concatenate them into lozza.js. There is also a script to do SPRT testing in bin/sprt.
Use bullet to train a 768->(N*2)->1 SqrRelu net and set NET_H1_SIZE to N in src/const.js. See src/bullet.rs for an example. Use the following command or bin/serialise_net to write the weights to src/weights.js:-
echo "WEIGHTS_B64 = \"$(base64 -w 0 mynet.bin)\";" > src/weights.js
Then rebuild using bin/build. If you change the activation function, tweak netEval in src/net.js to suit.
- https://nodejs.org - Node
- https://www.chessprogramming.org/Main_Page - Chess programming wiki
- https://computerchess.org.uk/ccrl/4040 - CCRL rating list
- https://backscattering.de/chess/uci - UCI protocol
- https://talkchess.com - Talkchess forums
- https://discord.gg/pntchvGU - Engine Programming Discord
- https://www.chessprogramming.org/Fruit - Early versions of Lozza used a HCE based on Fruit 2.1
