Introduction

Publishing Date: 21 November 2016.

Theodore Pringle had posted an announcement to the "fc-solve-discuss" group, where he said that he ran a Freecell solver over all the deals in the 8 milliard (1 to 8,589,934,591) Freecell Pro deals range which are based on the original Microsoft FreeCell dealing. He ended up discovering that there are 102,032 impossible deals and 46 intractable deals. Further analysis reduced the number of intractable deals down to 9 - see the updated list.

I (= Shlomi Fish) set out to determine the solvability of these intractable deals while using Freecell Solver's depth_dbm_fc_solver, which is a solver which occupies relatively little RAM, and aims to completely scan all positions in a board and conclusively determine whether it is solvable or not. That solver was ran on an Amazon Web Services (“AWS”) EC2 node with 256 GB of RAM. (Thanks to Jonathan Ringstad for the suggestion to use AWS.)