set-argb-benchmark.rkt

#lang racket

(require racket/draw net/url)

(define bm1
  (call/input-url (string->url "http://i.imgur.com/RU8MN.png") get-pure-port
  ;; Just a 500x500 image
   (λ (in) (make-object bitmap% in 'unknown/alpha))))
(define width (send bm1 get-width))
(define height (send bm1 get-height))
(define bytes (make-bytes (* 4 width height)))
(send bm1 get-argb-pixels 0 0 width height bytes #f #t)

(define bm (make-object bitmap% width height #f #t))

(define (one-run)
  (define-values (results cpu real gc)
    (time-apply (λ() (send bm set-argb-pixels 0 0 width height
                           bytes #f #t))
                '()))
  real)
(one-run) ; warm up the JIT

(display "Running tests")
(define times (for/list ([i (in-range 20)])
                (display ".") (flush-output)
                (one-run)))
(define average (exact->inexact (/ (apply + times) (length times))))
(define stddev (sqrt (/ (for/sum ([time times]) (sqr (- time average)))
                      (sub1 (length times)))))
(define std-err-of-mean (/ stddev (sqrt (length times))))
(set! std-err-of-mean (/ (floor (* std-err-of-mean 10.0)) 10.0))
(printf "\n~a ± ~a msec\n" average std-err-of-mean)