Stefan Pohl Computer Chess

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Patricia - the EAS ChessEngine

The most aggressive superhuman engine ever created

"Patricia is brilliant" - Ed Schroeder (Computerchess legend, author of Rebel engine and famous chesscomputers (Mephisto MM IV, Polgar, Milano, Risc and many more!))

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 3500; she can put up a solid fight against top engines, and can crush any human or weak engine that dares to oppose her.

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.

2024/12/03 Patricia 4.0 released. Download here

Jim Ablett made Windows/Linux and Android binaries, which do not have and Virus-alerts or Windows-permission errors, like the Patricia 4.0 binary on Patricia GitHub. Download here

(On my new AMD Ryzen machines, patricia_4_64_ja_bmi2 binary is the fastest, but mention, older AMD CPUs support bmi2 only per emulation, so other binaries should run faster there: Just try the binaries by Jim out on your system)

My small Gambit Opening-book (using J.Noomens Gambit-files) for Patricia is here

Folder with DroidFish and Patricia 3.1 and Patricia 4 here

ArenaGUI (Windows) with Patricia 4.0 installed and ready for playing 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 4.0 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 4.0. You can see the result in the Full UHO Ratinglist

Here the bottom of the Full UHO Ratinglist:

95 Stockfish final HCE : 3480 4 4 19000 40.4% 3552 38.8% 96 Slow Chess 2.9 avx2 : 3457 4 4 19000 38.4% 3546 43.2% 97 Rebel Extreme avx2 : 3413 4 4 14000 34.0% 3531 39.3% 98 Patricia 4.0 avx2 : 3392 4 4 14000 31.4% 3531 32.2% 99 Revenge 1.0 avx2 : 3367 5 5 15000 18.3% 3638 30.3% 100 Patricia 3.1 avx2 : 3220 6 6 14000 14.7% 3531 21.1%

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 432481 51.61% 38.03% 05.49% 66 Patricia 3.1 avx2 2 340432 46.96% 29.39% 03.46% 70 Patricia 4.0 avx2 3 253682 37.88% 23.88% 08.79% 75 Rebel Extreme avx2 4 221083 32.46% 23.04% 09.25% 71 Velvet 8.1.0 risky 5 204351 34.75% 22.22% 10.27% 73 Velvet 8.0.0 risky 6 200919 31.18% 29.46% 17.09% 71 Revenge 1.0 avx2 7 195881 21.25% 26.18% 09.40% 70 Stockfish 16 230630 8 193732 22.08% 24.73% 08.71% 70 Stockfish 16.1 240224 9 189267 25.24% 24.69% 13.42% 72 Velvet 7.0.0 avx2 10 187447 24.86% 20.78% 10.07% 75 Rebel EAS 2.0 avx2

That there is an EAS regression to Patricia 3.1 is no surprise for me: Gaining +172 Celo must lead to such a regression. But IMHO the EAS-Score is still very, very impressive: Better than all other aggressive playing engines and way better than Stockfish 16. And Stockfish 17 has only 163866 EAS-points, so Patricia 4 has more than twice as many points as the latest Stockfish. Awesome!

And, Patricia 4.0 has the smallest number of bad draws (3.46%) of all tested engines (better than Patricia 3.1 here !!!)

Here 20 impressive wins of Patricia 4.0 in this testrun in the pgn-viewer (engines started thinking at move 7).

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