12 October 2012

Scribe : Emma

Present: Lee, Micah, Zeke, Tom, Emma, Kwaku

Administrativia
Lee - pushing things incrementally forward; potential meeting with Sumit Gulwani's colleague in Boston; meeting one of Kourash Dani's new students; corresponding with David Clark (tree GP - makes more sense than Push), will try using lexicase selection on it, geometric semantic crossovers things to add to Clojush (random on failure to combat reproduction default when crossover fails due to child size, i.e. fail to random instead of mom)

Tom's suggestion for handling bloat: use simplification operator BEFORE fitness evaluation.

David Clark is interested in a new crossover operator that swaps the chunks of code that are crossed over.

Status Stuff
Status updates were framed primarily by issues of bloat and a desire to find better operators that either adapt to the state of the system or adapt to the particular parameters of the problem. In unrelated updates, Zeke is doing a Public Health hackathon and wanted to know if anyone had suggestions for uses of GP in this context.

Tom: Geometric Semantic Crossover gets really big really fast

Micah: Discuss places where humans are systematically outperformed by algorithms. Perhaps these are places that would be a good place to attempt to produce better algorithms for with GP.

Lee - implementing Family Feud

Tom - implementing deletion operators; having problems with random code generation (should perhaps be problem-specific) -> this is particularly problematic for language control structures

Lee (in response to some of Tom's concern) - We should seriously consider implementing a notion of scope -> using tag space machines to capture scope (where the tag space is a stack of frames) -> maybe something halfway between push and tsm?

Consider the fact that not having scope makes it considerably more difficult to evolve larger programs.

Problems with variation operators - as a group, we're really leaning towards

Zeke - interested in adaptive operators to handle plateaus

Issues with simplification - it's really a mutation-delete operator.

Paper for next time
Learning Programs : a Hierarchical Bayesian Approach

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