So maybe I should just have a smaller size bound? (the 10 in the 'gen-exp' function)
Really, perhaps, what I should do is not have a smaller size bound but instead just make the number of tests I do (32 in the currently pushed thing) depend on how long I've been testing. Robby On Fri, Jan 4, 2013 at 4:42 PM, Neil Toronto <neil.toro...@gmail.com> wrote: > On 01/04/2013 03:06 PM, Robby Findler wrote: > >> Very cool! I've run into this problem a few times. >> >> And here's an example where it happens right now .... >> >> http://drdr.racket-lang.org/**26021/collects/tests/future/** >> random-future.rkt<http://drdr.racket-lang.org/26021/collects/tests/future/random-future.rkt> >> > > Yeah, your problem is very similar. The difference is that in my case, I > had averages and variance that changed with the number of tests I wanted to > run. If I understand correctly how Redex generates terms, you're getting > independent, random programs from a fixed distribution. It just happens > that the distribution of program sizes has a *lot* of variance - it has a > "fat tail". > > I'd try simple rejection sampling first: > > (define gen-exp (let ([f (generate-term fut exp)]) > (λ () > (define t (f 10)) > (cond [(> (length (flatten t)) n) (gen-exp)] > [else t])))) > > When I had n = 100 and a `printf' that printed expression sizes, I got > output like this from running (gen-exp): > > 375 > 5092 > 45318 > 2331 > 2184 > 20 > > I didn't see more than 13 rejections in about 30 samples (most were around > 3-6), so the rejection loop seems fast enough. > > If you actually want unbounded program sizes, there are other rejection > methods that'll thin the tail of your distribution without zeroing it out. > But you probably don't want that. > > Neil ⊥ > >
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