Ah, indeed. I'm calling `random` in the closure now. Fixing that removes the anomaly.
Sam On Thu, Aug 22, 2013 at 11:05 AM, Matthew Flatt <mfl...@cs.utah.edu> wrote: > At Thu, 22 Aug 2013 10:59:35 -0400, Sam Tobin-Hochstadt wrote: >> This short program generates a lot of closures, and thus doesn't run very >> fast. >> >> #lang racket/base >> >> (require racket/flonum) >> >> (define (Point x0 x1 y0 y1) >> (list (λ () (let ([x (- x1 x0)] [y (- y1 y0)]) >> (flsqrt (+ (* x x) (* y y))))))) >> >> (define iter 1e4) >> (for ([i (in-range iter)]) >> (define p (Point (random) (random) (random) (random))) >> (define f (car p)) >> (for ([i (in-range 1e3)]) >> (f))) >> >> I tried manually inlining `Point` by replacing `define` with >> `define-syntax-rule`, and the program gets about 8x *slower*. I don't >> have any idea why this is happening, especially since `Point` is >> actually inlined by the optimizer in the `define` case. >> >> Any idea why this might be? > > Using `define-syntax-rule' changes the program from > > (let ([x (random)]) > (call-a-lot (lambda () x))) > > to > > (call-a-lot (lambda () (random))) > > > Did you mean to try > > (define (Point x0 x1 y0 y1) > (let ([x (- x1 x0)] [y (- y1 y0)]) > (let ([v (flsqrt (+ (* x x) (* y y)))]) > (list (λ () v))))) > > ? > _________________________ Racket Developers list: http://lists.racket-lang.org/dev
