18 September 2013

Meeting Notes

Present: Lee, Tom (scribe), Dave, Omri, Frode


Dave is moving on 🙁


Frode will be working on getting used to doing Clojush runs and getting back into writing Clojure code.


  • Omri is trying some things related to using Xerox machines for SIMD parallelism using stacked transparencies.
  • Unfortunately, adding new stacks in Clojush for just one example file is difficult, and therefore the easiest thing to do is to just change the global definition of the stacks.


  • ULTRA with many noops. This sounds interesting and potentially useful for allowing evolution to determine the correct amounts of noops.
    • Adding noops effectively increases the alternation rate so that it can be set lower.
    • Tom suggests using a fixed program size to encourage homology.
    • A good project would be to look at evolving populations to see how much homology exists, especially comparing something like ULTRA with normal genetic operators.
  • If anyone wants to work on calc or other software projects, talk to Lee!


  • Implemented the change problem, which isn’t as difficult as it first appeared, since it may be possible to do without exec stack manipulations and only integer arithmetic.
    • Tom will try some runs with only integers.
    • Tom is interested in general in doing some sort of Linear Push with ULTRA, which may help with matching instructions that need structure with the right connections.
  • Bagging and other ensemble techniques are potentially interesting!

Pre-Meeting Agenda

Things Tom wants to discuss:

  • Using ML ensemble techniques to combine solutions from multiple GP runs into single solution
  • Feature selection might be useful, especially for lexicase!
  • The US Change Problem
    • implemented and started testing
    • no solutions so far, but some very close misses, such as some that miss 2 to 5 cases out of every 25
    • It seems that ULTRA is having a hard time using semantic parentheses for instructions that need them, such as exec_y, exec_if, and exec_do*times.
      • I would be interested in trying some paren-free PushGP, where instruction groupings are somehow baked into instructions that need them. Or maybe, those instructions always start a paren, and only the ending paren can vary.
  • I’ve been timing the US Change runs, and am starting to get results as to which nodes of the cluster they are most efficient for.

Lee adds:

  • Noops and ULTRA.
  • Results for CREST/COW

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