Random Move Chess aka Infinite Monkey Chess

Two monkeys sit across from each other at a chess table. Both make completely random yet legal moves for eternity. Who wins? How often?


First, here is an example game run with these rules looks like:


After running approximately 500 games here is the resulting ending:


Interestingly, the first-move advantage still holds in this absurd variant. My initial guess of games that would end in checkmate was approximately 2%… nowhere near the actual 26%. The fact that stalemates are significantly lower than checkmates also is a bit curious. I am sure there is lots of room here for chess theory but I have no real desire to touch that.

Notes on the implementation

  • Castling / Au Passant-ing is possible and occurred
  • Pawns randomly select which piece to be promoted to (which makes the games really funny to watch)
  • Draw by repetition occurs after 200 moves without a piece being captured
  • Each game takes ~1.5 minutes on my school laptop

This was created using a fork of ChessPeace created by Zachary Danziger in Matlab. There is no way I would be able to scratch the surface of this problem without his work: so many thanks to him. I’d upload the code but its 98% his. The little work I did was to increase the draw by repetition threshold, trim unnecessary code, cut down on fprintfs, induce looping and an overall scoring system.


One thought on “Random Move Chess aka Infinite Monkey Chess

  1. Pingback: Infinite Monkey Chess Part II | Barron Wasteland

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s