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Long and skinny knights tours: the FDR approach.

Bill Roscoe ( OUCL )

Don Knuth gave a talk here recently in which he investigated patterns of knight's tours in 3xN boards: finding
what sorts of tours there are and who many of them there are.  Naturally I decided to investigate this with FDR
(though I found it equally possible to handle 4xN).  This has led to

  1. A linear-time way of searching for knights tours directly in 3xN and 4xN boards, using inductive compression.
  2. The best examples of FDR-driven (non data independent) induction I have ever seen.
  3. A completely new technique for getting FDR to ignore pointless states in a search.  [Specifically: given a compressed partial system, how do you get it not to do a lot of work exploring branches where that partial
    system cannot  reach the target "done" event.]
  4. A technique for counting and enumerating all the traces of a system with length K or less that end in done.
  5. The potentially automatic generation of recurrence relations that govern the number of knight's tours in 3xN and 4xN boards.




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