Re: map-par slower than map

[Damien Mattei]

the code did not worked when data length were more little than number of
cpus (6 on my host) (iota 5) returns #unsepcified:

scheme@(guile-user)> (use-modules (ice-9 threads))
scheme@(guile-user)> {v <+ (list->vector (iota 5))}
#(0 1 2 3 4)
scheme@(guile-user)> (par-map-vector sqrt v)
scheme@(guile-user)> {v <+ (list->vector (iota 20))}
#(0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19)
scheme@(guile-user)> (par-map-vector sqrt v)
#(0 1 1.4142135623730951 1.7320508075688772 2 2.23606797749979
2.449489742783178 2.6457513110645907 2.8284271247461903 3
3.1622776601683795 3.3166247903554 3.4641016151377544 3.605551275463989
3.7416573867739413 3.872983346207417 4 4.123105625617661 4.242640687119285
4.358898943540674)
scheme@(guile-user)> (current-processor-count)
6
scheme@(guile-user)> {v <+ (list->vector (iota 6))}
#(0 1 2 3 4 5)
scheme@(guile-user)> (par-map-vector sqrt v)
#(0 1 1.4142135623730951 1.7320508075688772 2 2.23606797749979)

so i modify it this way:

(define* (par-map-vector proc input
                         #:optional
                         (max-thread (current-processor-count)))

  (if (< (vector-length input) max-thread)

      (list->vector (map proc (vector->list input))) ;; less data than
threads or CPUs

      (let* ((block-size (quotient (vector-length input) max-thread))
    (rest (remainder (vector-length input) max-thread))
    (output (make-vector (vector-length input) #f)))

(when (not (zero? block-size))

 (let ((mtx (make-mutex))
(cnd (make-condition-variable))
(n 0))

   (fold

    (lambda (scale output)

      (begin-thread

(let lp ((i 0))
 (when (< i block-size)
   (let ((i (+ i (* scale block-size))))
     (vector-set! output i (proc (vector-ref input i))))
   (lp (1+ i))))

(with-mutex mtx
   (set! n (1+ n))
   (signal-condition-variable cnd)))
      output)

    output
    (iota max-thread))

   (with-mutex mtx
(while (not (< n max-thread))
      (wait-condition-variable cnd mtx))))

 (let ((base (- (vector-length input) rest)))
   (let lp ((i 0))
     (when (< i rest)
(let ((i (+ i base)))
 (vector-set! output i (proc (vector-ref input i))))
(lp (1+ i)))))

 output))))

now it works but crash randomly, not even at the same stage, i continue to
test and debug....


On Thu, Oct 13, 2022 at 1:57 PM Damien Mattei <damien.mattei@gmail.com>
wrote:

> sorry google always do reply to single author...
>
> ---------- Forwarded message ---------
> From: Damien Mattei <damien.mattei@gmail.com>
> Date: Thu, Oct 13, 2022 at 1:56 PM
> Subject: Re: map-par slower than map
> To: Olivier Dion <olivier.dion@polymtl.ca>
>
>
> ah just at the end? i had noticed, but i get #unspecifeid ? so my new code
> is not good if your procedure is, i will check it,thanks.
> Damien
>
> On Thu, Oct 13, 2022 at 1:00 PM Olivier Dion <olivier.dion@polymtl.ca>
> wrote:
>
>> On Thu, 13 Oct 2022, Damien Mattei <damien.mattei@gmail.com> wrote:
>> > i trying to use your code but it seems there is a ) mismatch
>> > somewhere?
>>
>> Right there's a missing ')' a the end to close the procedure, sorry
>> about that.
>>
>> --
>> Olivier Dion
>> oldiob.dev
>>
>