Leela Chess Zero Blog

After quite a long delay we are releasing an update to Lc0, new version is v0.21.2.

Download here.

Congrats. :)

2019-05-26 UPDATE: Temporary server is up again.
2019-05-25 UPDATE2: Turns out cloud instance was preemtable, so it was preempted, no training again for now.
2019-05-25 UPDATE: We’ve been donated a temporary AWS cloud instance for the time of the main server downtime! Training is back up, but only for test53, test40 is still paused.
2019-05-23 UPDATE: PSU seems to be in order, replugging all cables didn’t help. The person who has access to the server has to travel again, no news expected until next week. :-(
2019-05-20 UPDATE: The server doesn’t react to a power button, so it’s not something trivial. Will take a more thorough look tomorrow.
2019-05-17 UPDATE: The person who has access to the server is currently travelling, until Sunday. That means that updated information about the server is expected in the beginning of the next week.

Today, May 10, 2019, Leela is playing in the first game of the high profile TCEC Season 15 Superfinal. Leela qualified after she cleared Division P undefeated, winning at least once head-to-head against every opponent except Houdini. Her opponent in the superfinal is Stockfish, who lost once to Leela head-to-head in Division P, but finished with a higher score by winning more games than Leela against the other Division P competitors.

To break the silence of lack of posts in this blog, let me write about Lc0 backends configuration, as it has been totally undocumented so far.
(For other options it’s possible to get rough idea of their meaning by running lc0 –help).

After the huge success of the xyzzy extension to the UCI protocol introduced in Lc0, it was decided to take it one step further and introduce z-machine compatibility to the chess engine, giving birth to LcZ.

This a quick note for people who use CuteChess and just upgraded to v0.21.1 from earlier versions.

Meaning of FPU-related parameters are changed in v0.21.1 , along with default values of those parameters.

Important!

The lczero.org server will be not available for ~24 hours starting at April 4th 20:00 UTC.

Training game generation will also not be possible during the downtime.

We recently did the 2nd LR drop for T40, and usually this is when the net approaches it’s strongest point (gains after the final LR drop are very small). External Elo tests show T40 is close to T30, and may have already passed. We will know more in the following few weeks. But coincidentally we found two major issues at the same time as the LR drop:

Lc0 did well in it’s first TCEC Superfinal appearance, but fell just short of winning the match, losing 49.5 to 50.5. Here are some overviews of the Superfinal: