On Fri, Jan 20, 2012 at 5:58 PM, Danny Yoo <d...@cs.wpi.edu> wrote: > For the upcoming version of WeScheme, I'm planning to use the real > 'compile' from Racket. I'm trying to better understand a part of the > compilation system. Here's a sample program I'm using to play: > > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > #lang racket/base > > (define ns (make-base-namespace)) > (define (do-compilation program) > (parameterize ([current-namespace ns] > [read-accept-reader #t]) > (define bytes (compile (read-syntax #f (open-input-string program)))) > (define op (open-output-bytes)) > (write bytes op) > (get-output-bytes op))) > > (define (do-compilation/fresh program) > (parameterize ([current-namespace (make-base-namespace)] > [read-accept-reader #t]) > (define bytes (compile (read-syntax #f (open-input-string program)))) > (define op (open-output-bytes)) > (write bytes op) > (get-output-bytes op))) > > (time > (for ([i 1000]) > (void (do-compilation "#lang racket/base\n\n(printf \"Hello world\")")))) > > (time > (for ([i 1000]) > (void (do-compilation/fresh "#lang racket/base\n\n(printf \"Hello > world\")")))) > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > > I see that the first do-compilation, the one that shares a namespace, > runs faster than the version that generates fresh namespaces. > > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > kui ~ $ racket measure-compile-time.rkt > cpu time: 2244 real time: 2242 gc time: 172 > cpu time: 5244 real time: 6144 gc time: 516 > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; > > I assume that the reason for the difference is because the first > version touches some namespace state that's used as a part of > compilation, so that future compilations can reuse that state.
The state there is the instantiation of racket/base I believe. > Question: is the first version vulnerable to a memory leak? That is, > let's say that I enforce all programs going through do-compilation to > be in a hardcoded set of designated #langs. Do I run the risk of > exhausting memory? All of the code that runs when the top-level of a module executes will only happen once per namespace. So I suppose the answer is "it depends". If you really need separate instantiations of the modules, then you cannot have just one namespace. Hope that's useful, Robby ____________________ Racket Users list: http://lists.racket-lang.org/users
