[racket-dev] Manual inlining destroys performance for this program

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 <mflatt at 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)))))
>
> ?
>