[R-sig-hpc] multicore performance question

[Mauricio Zambrano-Bigiarini]

On 09/07/12 14:01, Rainer M Krug wrote:
>
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> On 09/07/12 12:18, Mauricio Zambrano-Bigiarini wrote:
>> I apologise. In my previous e-mail I did not write the time spent in each function:
>>
>> # No multicore nr<- 500 ; X<- matrix(rnorm(1000), ncol=30, nrow=nr) set.seed(100)
>> system.time( unlist(lapply(1:nr, FUN=fn1, x=X)) ) #   user  system elapsed #  0.013   0.000
>> 0.013
>>
>> # multicore nr<- 500 ; X<- matrix(rnorm(1000), ncol=30, nrow=nr) set.seed(100) system.time(
>> unlist(mclapply(1:nr, FUN=fn1, x=X, mc.cores=6)) ) #   user  system elapsed #  0.030   0.380
>> 0.125
>>
>> Running on RHEL6 (64) with 8 cores.
>
> Typical for communication: trying to distribute the job to 8 cores, doing the calculations,
> getting the data back, assemble it ->  longer then the calculations on one core.

Thanks for your feedback Rainer.

In fact, after doing the same test for a test function with a much 
longer computation time, the time saving was 43% by using 6 cores, wrt 
the time spent without the multicore package.


All the best,

Mauricio

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>
> Cheers,
>
> Rainer
>
>>
>> Thanks in advance,
>>
>> Mauricio
>>
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