Nilatac suicide chess engine

About Nilatac

Nilatac is a suicide chess engine. It plays according to international rules (the player being stalemated wins). See the Footnote for caveats.

The fun thing about suicide chess, from a software engineer's point of view, is that it was long believed to be solvable, meaning that a computer could produce a game tree ("proof") in which White wins regardless of Black's defense. In fact, Mark Watkins solved it in 2016 (I would estimate that around 20% of the work was done by other engines, including Nilatac). Some lines, such as 1. e3 d5 or 1. e3 e5, are trivially solvable by average players. Other lines, like 1. e3 b6, took years of computing time from several different chess programs.

Nilatac was developed mostly between 2001 and 2003. I haven't worked on the code recently, although I did do some minor opening research, notably solving 1. e3 Nh6 in 2012. Nilatac and its weakened sibling CatNail are registered on Lichess and usually online. Before, they were active on FICS (where CatNail played over 1.2 million games).




In 2012 and 2013 I spent some time rewriting a new version from scratch, called Colibri. So far the only working component are the 5-men endgame tables (browsable online). Time permitting, I'd like to rewrite the PNS engine as well to try and solve a few more openings. But it's the bad kind of "time permitting", the kind that tends never to happen.


Nilatac is free software. Get the source code!

I will seed the EGTB files on torrents once anybody asks. :-)


Copyright 2001-2020 Cătălin Frâncu

Nilatac's source code is released under the GNU General Public License, version 2.

Nilatac's opening book and endgame tables are released under the Creative Commons Attribution-ShareAlike 3.0 Unported License.


Nilatac originally worked according to FICS rules, in which stalemate is a win for the player with fewer remaining pieces, or a draw if both sides have the same number of pieces. When I moved to Lichess I updated the rules only partially due to lack of time.