Stefan Pohl Computer Chess

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Patricia - the EAS ChessEngine

The most aggressive superhuman engine ever created

Patricia by Adam Kulju is the first engine besides Ed Schroeder's Rebel EAS, using my EAS-Tool (= Engine Aggressiveness Statistics Tool) to make the engine playing more aggressive:

It's worth noting that Patricia is still well into superhuman territory, with an estimated CCRL elo of 3300-3350; she can put up a solid fight against top engines, and can crush any human or weak engine that dares to oppose her.

Patricia, with an EAS score of 425,000 in gauntlet testing, is leaps and bounds above any engine that has ever existed in terms of attacking, sacrificing, and playing stylishly.

If you think Patricia is a cool project, please spread the word of it! There are lots of people interested in an aggressive engine, whether it be for sparring or for other purposes, and greater awareness of what should be the undisputed queen of style would make their wish come true.

Since the 1950s, the only goal of computerchess was gaining Elo. But in these days of superstrong engines beyond 3700+ Elo, IMHO it makes a lot of sense, to make engines playing more spectacular, aggressive and interesting, instead of just gaining more and more Elo... Since my EAS-Tool was made, it is possible for the first time, to measure the aggressiveness of engines. And so, using the EAS-Tool, to make an engine playing more aggressive, is the next logical step of development in computerchess.

2024/07/14 Patricia 3.0 released. Download here

Android builds (not by A.Kulju, so use at own risk) here

The author of Patricia (Adam Kulju) wrote this:

"Patricia is, per the EAS tool, unquestionably the most aggressive superhuman chess engine ever created (and the most aggressive engine of any kind that I currently know of).

The metric that Patricia's aggression claims are based off of is Stefan Pohl's EAS-Tool, which is the most well known and well regarded tool for determining the aggressiveness of chess engines. It looks at a combination of factors, such as sacrifice rate, short win rate, and unnecessary draw rate, and outputs a score that captures how "exciting" an engine tends to play.
A huge shoutout to Stefan Pohl. His EAS Tool works wonderfully, makes properly and objectively testing for increase aggression possible, and is the measure by which Patricia development progressed. He was also very invested in Patricia's development and explained many features of the EAS tool to me so that I had a better understanding of what was a sacrifice and what wasn't. He has put a lot of time into quantifying style, and I am happy to have Patricia be a proof-of concept and culmination of his ideas."

I did a testrun of Patricia 3.0 vs. 14 weaker engines of my full UHO ratinglist. Mention, weaker engines means here 3500+ Celo, so these engine are way too strong for Patricia 3.0. You can see the result in the Full UHO Ratinglist

Here the bottom of the Full UHO Ratinglist:

Program Celo + - Games Score Av.Op. Draws

65 Viridithas 11.0.0 avx2 : 3511 4 4 17000 39.2% 3593 45.2% 66 Velvet 7.0.0 avx2 : 3506 5 5 16000 30.7% 3655 43.1% 67 Stockfish final HCE : 3501 4 4 15000 37.6% 3594 38.6% 68 Slow Chess 2.9 avx2 : 3476 4 4 15000 35.6% 3587 43.3% 69 Revenge 1.0 avx2 : 3387 5 5 15000 18.3% 3659 30.3% 70 Patricia 3.0 avx2 : 3237 6 6 14000 14.5% 3551 21.2%

And now, see the top of the EAS full Ratinglist (calculated out of the games played for the Full UHO Ratinglist):

bad avg.win Rank EAS-Score sacs shorts draws moves Engine/player ------------------------------------------------------------------- 1 384942 52.55% 35.77% 05.19% 69 Patricia 3.0 avx2 2 198431 22.77% 26.15% 08.34% 69 Stockfish 16.1 240224 3 197919 31.18% 29.46% 17.09% 71 Revenge 1.0 avx2 4 192881 21.25% 26.18% 09.40% 70 Stockfish 16 230630 5 186267 25.24% 24.69% 13.42% 72 Velvet 7.0.0 avx2 6 181381 20.24% 25.04% 10.47% 70 Stockfish 15.1 221204 7 161767 25.14% 21.45% 13.73% 72 Velvet 7.3.0 avx2 8 158922 16.43% 26.49% 11.07% 69 Torch 2 popavx2 9 151721 15.63% 27.12% 13.45% 69 Torch 1 popavx2

This result is really impressive, especially when mentioning, that Patricia 3 has won only 548 out of 14000 played games, because the opponents were way too strong !!! (Another impressive proof, that my EAS-Tool recognizes the playing-style of an engine correctly, even though, the opponents were too strong)

Here 10 impressive wins of Patricia 3.0 in this testrun in the pgn-viewer (engines started thinking at move 7). In the first game, Patricia 3.0 mates Stockfish final HCE (= last Stockfish without nnue-net, around +30 Celo stronger than Stockfish 11) in 35 moves. Insane!

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I did a testrun of Patricia 2.0 and Patricia 3.0 vs. 10 engines (strength around Rybka 4.1), which fits the strength of Patricia 2.0 very well, for an EAS-calculation (short wins move-limit fixed to 60 moves). 10000 games, 3min+1sec, singlethread. Balanced openings, engines start thinking from move 9.

Download the played games: here

Program Celo + - Games Score Av.Op. Draws

1 Patricia 3.0 : 3426 5 5 10000 69.1 % 3284 26.2 % 2 Houdini 1.5a : 3314 11 11 2000 45.3 % 3349 27.1 % 3 Komodo 5 : 3313 11 11 2000 45.1 % 3349 29.8 % 4 Critter 1.6a : 3309 11 11 2000 44.6 % 3349 30.3 % 5 Andscacs 0.88 : 3307 11 11 2000 44.3 % 3349 29.4 % 6 Nirvanachess 2.4 : 3293 11 11 2000 42.4 % 3349 30.6 % 7 Hannibal 1.7 : 3284 10 10 2000 41.2 % 3349 29.9 % 8 Rybka 4.1 : 3282 11 11 2000 41.0 % 3349 29.7 % 9 Texel 1.7 : 3274 11 11 2000 39.9 % 3349 31.1 % 10 Patricia 2.0 : 3272 5 5 10000 48.4 % 3284 33.1 % 11 Laser 1.5 : 3233 12 12 2000 34.7 % 3349 28.3 % 12 Princhess 0.16 : 3227 11 11 2000 33.9 % 3349 30.4 %

Games : 20000 (finished)

White Wins : 7787 (38.9 %) Black Wins : 6284 (31.4 %) Draws : 5929 (29.6 %)

Here the EAS-calculation of these 20000 games (short win movelimit set to 60):

bad avg.win Rank EAS-Score sacs shorts draws moves Engine/player ------------------------------------------------------------------- 1 350507 48.56% 35.10% 03.66% 69 Patricia 3.0 2 339941 44.01% 36.20% 04.84% 67 Patricia 2.0 3 121961 03.21% 53.38% 42.11% 62 Andscacs 0.88 4 121522 05.59% 51.53% 40.17% 63 Critter 1.6a 5 120395 01.91% 50.86% 42.26% 62 Rybka 4.1 6 119444 03.65% 54.50% 40.18% 62 Laser 1.5 7 116762 03.49% 49.90% 41.89% 62 Texel 1.7 8 100067 03.14% 44.13% 38.66% 65 Komodo 5 9 98770 03.14% 47.23% 45.99% 64 Nirvanachess 2.4 10 96626 03.31% 45.74% 44.10% 65 Houdini 1.5a 11 87553 03.23% 43.54% 44.89% 65 Hannibal 1.7 12 62934 01.07% 29.68% 32.07% 72 Princhess 0.16 ------------------------------------------------------------------- *** Average length of all won games: 67 moves

The fact, that the opponents (which all are at the same strength-level than Particia 2.0) have such high numbers/points in the short wins, comes from the fact, that Patricia 2.0 and 3.0 loose a lot of games quickly, because Patricia plays so risky and plays so much sacs - that leads to quick losses, if something goes wrong... So, this definitly makes sense.