Stockfish Wins TCEC S20; CCC 'Rapid 2021' Underway

For the previous post on the world's top two engine vs. engine competitions, see TCEC S20 Sufi Underway; CCC Back in the Saddle (January 2021). If you prefer not to click through to that report, the following is a summary.

TCEC: S20 DivP finished with LCZero and Stockfish in a dead heat and an identical score, +24-4=28. That result includes +2-2=6 in their head-to-head mini-match. The two engines have already started their S20 final match, which is tied at one win each. • CCC: After a four month break for technical problems that started in CCC15, the CCC is back with 'Rapid 2021: Qualifiers'. The site's 'Info' tab lists a total of six events for 'CCC Rapid 2021'.

Since that report, TCEC S20 has finished and the CCC 'Rapid 2021' is in full swing. The following is a report on the current status of both competitions.

TCEC: Stockfish beat LCZero in the S20 Superfinal match +14-8=78, for a convincing final score of 53.0-47.0. The victory was clinched after 95 games. This was Stockfish's third straight victory over LCZero, as documented by the list of posts on this blog that recorded the winners:-

• 2020-10-26: Stockfish Wins TCEC S19; CCC15 Still Halted • Stockfish - LCZero, +18-9=73
• 2020-07-20: Stockfish Wins TCEC S18; Leela Wins CCC14 • Stockfish - LCZero; +23-16=61
• 2020-04-27: Leela Beat Stockfish in TCEC S17 & CCC13 Finals • LCZero - Stockfish, +17-12=71

The dates of the posts show that a TCEC season lasts about three months, including other events that typically run between seasons. Now that S20 is finished, we can expect a few side events over the next weeks.

CCC: Let's have an overview of the 'CCC Rapid 2021' events that have been running since the previous report, 'CCC Back in the Saddle':-

• The 'Qualifiers' event finished with Rubichess and Winter 1st and 2nd, well ahead of six other engines.
• The 'NNUE League' finished with [Komodo] Dragon well ahead of 2nd Ethereal and 3rd Igel, which finished ahead of five other engines.
• The 'Main League' is now running, with six engines -- including two stars of yesteryear, Stockfish Classic [pre-NNUE] and Komodo -- plus the two top engines from the 'Qualifiers'.

The next event, 'NN vs Classic', will see Stockfish and Leela enter the competition along with the top three engines from the 'NNUE League' and the top five engines from the 'Main League'. After that we will see an 'Elite Round' of six engines followed by a 'Finals' match between the top two engines.

[For further information from the various stakeholders in the engine-to-engine events, see the tab 'TCEC/CCC Links' at the top of this page. • NB: Leela = LC0 = LCzero]