Leela in TCEC FRC Events

My previous post Breaking the 4000 Barrier (April 2023) was about chess960 ratings for engines. I wrote,

The fourth [rating] list was based on chess960 games. Here are the top 25 engines from that list.

I received a question -- @nicbentulan: Is Leela on this list? (twitter.com) -- against the Twitter anchor for the post. A quick look at the list reveals that Leela is on the most recent list at no.42, rated 3008:-

no.42 • Lc0 0.29.0 CPU_744706 • 3008

That rating is nearly 1000 points lower than no.1 'Stockfish 15.1', currently rated 4005. The Lc0 rating looks dubious, given that Leela is currently one of the top three engines in the world. How has it done in TCEC FRC competitions? Following is a list of posts from this blog:-

• 2022-07-30: TCEC C960 FRC5 • In the 'Final League', Stockfish and LCZero finished in a tie for 1st and 2nd to qualify for the 'Final Match'. [...] In the 'Final Match' Stockfish beat LCZero +17-13=20.'
• 2022-01-22: TCEC C960 FRC4 • 'Stockfish and LCZero tied for 1st/2nd in the [TCEC] FRC4 'Final League', a point ahead of KomodoDragon. Stockfish beat LCZero +13-9=28 in the Final.'
• 2021-03-27: TCEC C960 FRC3 • 'In the 'FRC 3' final, KomodoDragon beat Stockfish by a score of +2-1=47.'
• 2020-12-26: TCEC FRC2 • 'In the FRC2 Final League, LCZero and Stockfish finished first and second to qualify for the 50-game final match. Stockfish beat LCZero +8-0=42.' [...] 'The first of the three posts above linked to Stockfish, the Strong (July 2014) on this blog, plus two other followup posts based on FRC1. FRC1 was held three and a half years before AlphaZero made waves with its revolutionary AI/NN technology, soon to be followed by Leela Chess Zero (aka LCZero / LC0).'
• 2014-08-02: TCEC Season 6 - Chess960 • 'After posting Stockfish, the Strong, winner of this year's TCEC Season 6 Special Event (chess960), I started looking at the games from the event. I couldn't find a crosstable, so I made one myself, shown below.'

Why is Leela so far down on the CCRL rating list? I'll leave that for the CCRL to answer.

Breaking the 4000 Barrier

The title comes from a recent post on my main blog Breaking the 3600 Barrier (April 2023), where the '3600 Barrier' refers to a chess rating level. In that post I wrote,

I see that there are four CCRL rating lists. Shown below are the top five engines from three of the lists.

Why didn't I show all four lists? Because the fourth list was based on chess960 games. Here are the top 25 engines from that list.

CCRL 40/2 FRC [C960] - Index

The most striking feature of the list is that the top engine, Stockfish 15.1, is rated over 4000. This is more than 250 points higher than the top rating shown on the '3600 Barrier' chart. In fact the top four engines on the CCRL FRC list are higher then the top engine on the earlier list. I couldn't determine why this is.

[NB: The domain given here (ccrl.chessdom.com) is not the same as the domain in the right sidebar (computerchess.org.uk), although the two sites appear to be identical. The ratings are based on the same database of games used to compute the CCRL 'Opening statistics'.]