Hi,
Attached is a benchmarking test that resizes a u8vector of RGB pixels into
half the size in each dimension using a pixel average.
I applied Peter's patch which inlines vector-ref and vector-set! procedures:
http://lists.nongnu.org/archive/html/chicken-hackers/2019-04/msg00041.html
With this patch, I see about a 2x speedup which is nice. I see vector_ref
and vector_set in the generated C code. However, the C code still has a
continuation call inside the main loop. Maybe someone can look into why
this is happening.
K.
PS. `convert` comes from imagemagick on most distros
;;; srfi-4 chicken benchmarking test
;;; /.chickens/be678994/bin/csc -k -m main -O5 srfi-4-stress-test.scm
;;;
;;; $ convert wizard: -resize 2000x-1 png:- | ./srfi-4-stress-test /tmp/wizard.png
(import stb-image stb-image-write
(only (chicken process-context) command-line-arguments)
(only (chicken time) time)
srfi-4)
(define fn-out (car (command-line-arguments)))
(define (image-half pixels w h c)
(define (half n) (quotient n 2))
(define hw (- (half w) 1))
(define hh (- (half h) 1))
(define (average a b c d) (quotient (+ a b c d) 4))
(define (ref p x y z) (u8vector-ref p (+ z (* c (+ x (* w y))))))
(let ((out (make-u8vector (* w h c))))
(do ((y 0 (+ y 1)))
((>= y hh))
(do ((x 0 (+ x 1)))
((>= x hw))
(do ((z 1 (+ z 1)))
((> z c))
(u8vector-set! out (+ z (* c (+ x (* hw y))))
(average (ref pixels (+ (* x 2) 0) (+ (* y 2) 0) z)
(ref pixels (+ (* x 2) 0) (+ (* y 2) 1) z)
(ref pixels (+ (* x 2) 1) (+ (* y 2) 0) z)
(ref pixels (+ (* x 2) 1) (+ (* y 2) 1) z) )))))
(values out hw hh c)))
(receive (pixels w h c) (read-image)
(with-output-to-file fn-out
(lambda ()
(receive (pixels w h c) (time (image-half pixels w h c))
(write-png pixels w h c)))))
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