A Gray Code for the Ideals of Acyclic Posets
(Enumerating Spider Squishings)

• These results were presented at the 26th South East Conference on Combinatorics, Graph Theory, and Computing, 1995. Here are some scans of the slides from that talk:
  Slide #1 Title slide.
  Slide #2 Background.
  Slide #3 A six element fence poset and its ideal graph.
  Slide #4 Spider = ayclic poset.
  Slide #5 Spider for overlay.    (Slide #5' Another spider.)
  Slide #6 (Slide #6') Spider = ayclic poset OVERLAY. Missing is a shoe overlay for showing some squishings (something like this and this).
  Slide #7a Slide #7b Slide #7c Spider close-ups showing continued branching.
  Slide #8 Parity difference is one of +1, 0, -1.
  Slide #9 Definitions; e.g., q-code, squishings.
  Slide #10 Allowed relations between q and r.
  Slide #11 The path traced out by the proof and by the algorithm.
  Slide #12 The relation between the proof and the algorithm.
  Slide #13 Non-recursive look at the algorithm.
  Slide #14 Second problem --- which ideal is first?
  Slide #15 Final slide: Open Questions.
  
• Gang (Kenny) Li now works for i2 Technologies in Dallas, Texas.
• Donald Knuth liked the Gray code so much that he couldn't resist developing his own implementation. See his CWEB program LI-RUSKEY .