I ran across a Freecell position that gives your solver (and others) difficulty. (The moves leading to this position are given below.) Here's what happened: I was playing with Freecell Pro and got into this position. When I checked the solvability, I got Yes, but I couldn't see how myself. I fumbled around a bit and then checked the solvability again, and it said No. This would not have been a surprise except the only difference from the first position was a reversible move (the three of clubs can be moved freely between two columns.) What a shock! I thought the solver always told the truth (or came to no conclusion at all.)
I reported the problem to Michael Keller and he suggested the newer version of FC Pro that has 3 solvers, including yours. Yours reports this position impossible. But the 3rd solver, Patsolve, reported it solvable -- whereever the 3 of clubs was placed. Using the solution generated by Patsolve I was able to see how to get out of the difficulty.
This is just my opinion, but it seems to me that if you are going to release a program to the public and call it a solver, then it is understandable if it can't come to a conclusion about certain positions, but it should at least come to the correct conclusion if it does.
#715037 Attempt: 5 NumFcs=4 (FCPro)
8h 5d 5c 5b 5a d5 65 65 68 65
6d 76 72 a2 6a 76 74 a7 6a 83
72 c6 38 7c a7 83 38 6a 83 c6
56 7c 38 83
Received on Sun Oct 18 2009 - 13:06:46 IST