Re: [Starpu-devel] About the prediction model of data transfer time

[Lennox Wu <lennox.wu@gmail.com>]

Hi Samuel,
Thanks for your answer :)
Now I understand the meaning of the formula "
topology->ncudagpus+topology->nopenclgpus".
But what's the meaning of the factor "2" ?

Best,
Lennox

2014-07-02 17:11 GMT+08:00 Samuel Thibault <samuel.thibault@ens-lyon.org>:
> Lennox Wu, le Wed 02 Jul 2014 16:48:52 +0800, a écrit :
>> I didn't find the prediction model from your papers(Was it written 
>> somewhere?),
>
> The paper about performance models is http://hal.inria.fr/inria-00421333
>
>> I  found the function  "starpu_transfer_predict", is it the prediction 
>> model?
>
> This is the data transfer prediction model.
>
>> I can't understand the meaning behind the fomular
>> "2*(topology->ncudagpus+topology->nopenclgpus)",
>> could anybody explain it?
>
> The data transfer prediction is very rough: since the measurement is
> done off-line, we divide by the number of the GPUs to account for
> contention in a quite rough manner.
>
> The task prediction models are in src/core/perfmodel,
> starting from starpu_model_expected_perf, which
> ends up for instance in perfmodel_history.c's
> _starpu_history_based_job_expected_perf for the simple average over
> history, or _starpu_regression_based_job_expected_perf for the
> regression-based model, etc.
>
> Samuel