OpenMP support

[Júlio Hoffimann]

Dear all,

Although we have an option for enabling OpenMP, i can't found the associated pragmas in the source.

How this option actually affects the build?

Best,

Júlio.

[John W. Eaton]

On 03/06/2013 06:54 PM, Júlio Hoffimann wrote:
> Dear all,
>
> Although we have an option for enabling OpenMP, i can't found the
> associated pragmas in the source.
>
> How this option actually affects the build?

I don't think that option currently does anything.

jwe

[Júlio Hoffimann]

I don't think that option currently does anything.

jwe

That was my feeling!

Any problem in adding some parallel for's in the source? It's embarrassing to see all those cores sleeping during intensive computations.

[Stefan Seefeld]

On 03/06/2013 07:27 PM, Júlio Hoffimann wrote:

>
>     I don't think that option currently does anything.
>
>     jwe
>
>
> That was my feeling!
>
> Any problem in adding some parallel for's in the source? It's
> embarrassing to see all those cores sleeping during intensive
> computations.

I think just adding parallel regions won't gain you much if any
performance improvements. In my experience you also need to carefully
profile performance and pin threads to cores to avoid cache conflicts.

FWIW,
    Stefan

--

      ...ich hab' noch einen Koffer in Berlin...

[Júlio Hoffimann]

I think just adding parallel regions won't gain you much if any
performance improvements. In my experience you also need to carefully
profile performance and pin threads to cores to avoid cache conflicts.

FWIW,
    Stefan

Hi Stefan,

I also had the same experience with my old laptop (Core 2 Duo). Indeed, adding parallel regions was irrelevant for performance because of core switching and related issues.

The scenario changes drastically with modern CPUs, my Intel i7 responds a lot different when i add parallel regions. There is effective scalability with 8 cores at hand, not much effort.

Best,

Júlio.