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:

Patricia 2.0, 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.

2024/04/04 Patricia 2.0 released. Download here


The author of Patricia (Adam Kulju) wrote this:

"Patricia 2.0 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.
It's worth noting that Patricia is still well into superhuman territory, with an estimated CCRL Elo of 3100-3150; she'll lose badly to top engines, but will still crush any human.
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."

Mention, Patricia 2.0 is still a very early version. Right now, Patricia does not support multithreading and there is still no skill-level, to reduce the playing-strength (for playing against Patricia as a human, this is needed!). 

I did a testrun of Patricia 2.0 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 and 874 spectacular wins of Patricia 2.0 (with at least a 2 pawn-units sac) (filtered by my Interesting Wins Search Tool): here 


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 looses a lot of games quickly, because it plays so risky and plays so much sacs - that leads to quick losses, if something goes wrong... So, this definitly makes sense.


Rank  EAS-Score  sacs   shorts  draws  moves  Engine/player 
   1    337941  44.01%  36.20%  04.84%   67   Patricia 2.0  
   2    134485  07.65%  54.34%  33.84%   61   Critter 1.6a  
   3    130651  02.60%  53.76%  35.44%   60   Rybka 4.1  
   4    125405  03.57%  55.61%  34.45%   61   Andscacs 0.88  
   5    121305  04.28%  56.03%  32.84%   61   Laser 1.5  
   6    106943  03.61%  45.10%  30.06%   64   Komodo 5  
   7    100754  04.08%  47.96%  36.93%   64   Houdini 1.5a  
   8    100360  05.03%  46.15%  35.51%   63   Texel 1.7  
   9     97459  03.85%  46.15%  36.69%   63   Nirvanachess 2.4  
  10     84082  04.61%  43.80%  37.65%   65   Hannibal 1.7  
  11     67447  01.51%  29.06%  24.70%   72   Princhess 0.16  
*** Average length of all won games:     65 moves

An EAS-Score of 337941 is very impressive. No other engine (except the 2300 Elo only OpenTal engine) has ever achieved more than 300000 EAS-points in my testings !!!

So, Patricia 2.0 is, right now, the most aggressive playing engine, which is on superhuman Elo-level and has a neural-net for much better positional understanding.

Download Patricia from the GitHub site of the author:


Download my EAS-Tool here

Download my Interesting Wins Search Tool here