[racket] Futures and shared data structure

Thanks for the prompt reply.

Disregard the noncollectable thing, that was a confusion on my side.
Still, my doubt remains about why my futures version is slower and not
parallel. I did read about the futures, but alas, I'm still in the dark
as to why it is behaving like it is.

My output to your suggested approach is

GC [minor] at 1514740 bytes; 818464 collected in 4 msec
GC [minor] at 2142928 bytes; 678980 collected in 4 msec
GC [minor] at 4424700 bytes; 1509104 collected in 12 msec
GC [minor] at 4999304 bytes; 614508 collected in 16 msec
GC [minor] at 8337384 bytes; 1957728 collected in 20 msec
GC [minor] at 10529324 bytes; 1709172 collected in 24 msec
GC [minor] at 14245196 bytes; 2815768 collected in 28 msec
GC [minor] at 19109972 bytes; 4515808 collected in 48 msec
GC [minor] at 20287336 bytes; 4153060 collected in 32 msec
GC [minor] at 416134292 bytes; -27108 collected in 1652 msec
cpu time: 2660 real time: 2657 gc time: 1652
cpu time: 1000 real time: 1001 gc time: 0
2 success(es) 0 failure(s) 0 error(s) 2 test(s) run
0

Which for me is not helpful. Any more suggestions?


On 12/20/2010 04:54 PM, Robby Findler wrote:
> I'm not sure about the uncollectable issue, but for the rest, try
> running in racket, enabling the debug log. Eg, if you save the file in
> x.rkt and do this:
> 
>   racket -W debug x.rkt
> 
> then you should see some messages telling you what is causing your
> future to get stuck.
> 
> Also, do be sure to read this if you haven't yet:
> 
>   http://docs.racket-lang.org/guide/performance.html#%28part._effective-futures%29
> 
> Robby
> 
> On Mon, Dec 20, 2010 at 12:47 PM, Eduardo Bellani <ebellani at gmail.com> wrote:
>> Hello all
>>
>> I am trying to understand futures, and I have generated to following
>> code to see how I would create reader futures. Unfortunately my futures
>> are not running in parallel and are taking more time that the serial
>> version. Besides that it seems to capture the vector in a way that it
>> becomes noncollectable by the GC.
>>
>> Could anyone give some hints as to why? (my version is "5.0.2" on Linux)
>>
>> #lang racket
>>
>> (require racket/future rackunit rackunit/text-ui)
>>
>> (define DATA (make-vector 99999999 'datum))
>>
>> (define-test-suite read-from-shared
>>  (test-suite "with futures"
>>              (check-equal?
>>               (time (let ([f (future (λ _ (read-data DATA)))])
>>                       (touch f)
>>                       (read-data DATA)))
>>               (void)))
>>
>>  (test-suite "no futures"
>>              (check-equal?
>>               (time (read-data DATA)
>>                     (read-data DATA))
>>               (void))))
>>
>> (define (read-data some-data)
>>  (for ([i (in-vector some-data)]) i))
>>
>> (run-tests read-from-shared)
>>
>>
>> Thanks
>>
>> --
>> Eduardo Bellani
>>
>> omnia mutantur, nihil interit.
>> _________________________________________________
>>  For list-related administrative tasks:
>>  http://lists.racket-lang.org/listinfo/users


-- 
Eduardo Bellani

omnia mutantur, nihil interit.