Critter

Critter

Critters origin

Critter is chess engine with UCI – User Chess Interface, created by Slovenian Richard Vida chess programmer. Critter is cross – platform and it is free to use for non-commercial purposes. Richard Vida start project Critter in late 2008, and its first release was in May 2009 under the name Critter 0.38. In January 2010 Vida release Critter 0.52, after that fallows six upgrades of Critter until November that same year. Last version Critter 1.6a was released in June year 2012.At first Critter was written in Objective – Pascal and compiled with Delphi, but because of x64 bit processor registers Richard Vida had to rewrite it in C++. Critter reached its highest achievement on ITC 2012 when he took a win over Rybka chess engine.

Critters structure

Critter have a search based on principle variations – this means that the algorithm looks for future moves for the both sides which are acceptable and which are expecting to be moved. Also Critter have technique called aspiration windows – this means that in order to reduce search, the algorithm creates so called window in which the algorithm expect to be moved, if by some chance the algorithm missed expected move the search will be started again and window will be created on base of the new search, this technique reduce the time of search for moves. Critter can search parallel with eight threads, and also use Gaviota table-bases. Critters code includes tapered eval – technique for evaluation of captured figures until that moment in time by creating two distinct results, one for start of game and one for end of game, while game is playing the result of taken figures is going between this to values. There is also score pair technique which is used to predict the chances of winning from the results in that particular moment, and to not forget Richard used operator overloads in the code and blockade detection for late game.

Strength analyze

The ability of finding original moves in the game is not omitted in Critter. On short way Critter has great ability to do this, but not so great in long term. Critter is faster in doing this on short term while Rybka his opponent is maybe better for long term. When we talk about position evaluation Critter can be found on the very second place on the table with four great chess engines. The speed of analyzes is not the best side of Critter, still he is on third place above the Rybka which is on the last place. Critter can also get in infinity loop if there is undefined analysis.

Differences from other chess engines

The creators of Critter says that maybe the only difference between Critter and the other chess engines except from ones that are cloned, is in exchange between Bishop and Knight – Critter will always choose Knight over the Bishop. They also say that there is no big difference in evaluation of positions on the board and they use “Singular extension” to eliminate moves.