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)))))
?
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