From: Maxime Boissonneault <maxime.boissonneault@calculquebec.ca>
To: Rhys Ulerich <rhys.ulerich@gmail.com>
Cc: gsl-discuss@sourceware.org
Subject: Re: Adding OpenMP support for some of the GSL functions
Date: Thu, 13 Dec 2012 21:07:00 -0000 [thread overview]
Message-ID: <50CA4378.6090204@calculquebec.ca> (raw)
In-Reply-To: <CAKDqugTG9EybSGqkaZr0z2y79-af2sF3TWx2qUMbwMXaOAbezA@mail.gmail.com>
Hi Rhys,
While that is true in theory, it is not applicable in practice, since
there can be no "return" within parallel sections. We need one parallel
section for each loop in this case.
Maxime
Le 2012-12-13 11:44, Rhys Ulerich a écrit :
>> This feels like you're getting a small
>> memory/cache bandwidth increase for the rkf45_apply level-1-BLAS-like
>> operations by using multiple cores but the cores are otherwise not
>> being used effectively. I say this because a state vector 1e6 doubles
>> long will not generally fit in cache. Adding more cores increases the
>> amount of cache available.
> Hmm... I tentatively take this back on re-thinking how you've added
> the #pragma omp lines to the rkf45.c file you attached elsewhere in
> this thread. Try using a single
> #pragma omp parallel
> and then individual lines like
> #pragma omp for
> at each for loop. Using
> #pragma omp parallel for
> repeatedly as you've done can introduce excess overhead, depending on
> your compiler, because it may incur unnecessary overhead.
>
> - Rhys
next prev parent reply other threads:[~2012-12-13 21:07 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-11 20:04 Maxime Boissonneault
2012-12-12 16:35 ` Frank Reininghaus
2012-12-12 21:11 ` Maxime Boissonneault
2012-12-12 21:41 ` Rhys Ulerich
2012-12-12 23:32 ` Maxime Boissonneault
2012-12-12 17:05 ` Rhys Ulerich
2012-12-12 21:13 ` Maxime Boissonneault
2012-12-12 21:36 ` Rhys Ulerich
2012-12-12 23:35 ` Maxime Boissonneault
2012-12-13 2:29 ` Rhys Ulerich
2012-12-13 13:22 ` Maxime Boissonneault
2012-12-13 15:53 ` Rhys Ulerich
2012-12-13 16:44 ` Rhys Ulerich
2012-12-13 21:07 ` Maxime Boissonneault [this message]
2012-12-13 21:05 ` Maxime Boissonneault
2012-12-13 21:14 ` Maxime Boissonneault
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