[Opm] New opm-repo

[Markus Blatt]

Hi,

On Tue, Mar 15, 2016 at 08:47:52AM +0000, Alf Birger Rustad wrote:
> Thanks for the announcement! There is one issue that I hope
> everybody with informed opinions can contribute to. Today, writing
> results is a performance bottleneck flow. Hence, we should find a
> way for flow to write results asynchronously, i.e., the simulator
> should not need to wait computing the next timestep while the
> results are written. It has been suggested to split out the writing
> in a separate process to accomplish this, but I am not sure how this
> could be done in a good way. Implementing the writer as a server
> seems like over-engineering, and we probably do not want to mandate
> MPI to run the simulator. The simplest option I can think of is
> splitting the writing to a new thread with openmp.

As I am the one who brought this up, I have to relativate this a bit.
I experienced this bottleneck for a parallel run with 8 cores. The
time spent for output was 31% of the total time. For a sequential run
it is probably below 10% but I have not measured it.

Minimizing the time for the ouput of a sequential run as proposed
comes at cost, too. We need to duplicate the memory.

What I am concerned about is that the output is not parallel at all
which will bite us more when using more cores. Having a dedicated
output core is just a first step. Ultimately, we need several cores
doing output in parallel in a parallel file format. But this can wait
some time, I guess.

Cheers,

Markus

-- 
Dr. Markus Blatt - HPC-Simulation-Software & Services http://www.dr-blatt.de
Hans-Bunte-Str. 8-10, 69123 Heidelberg, Germany,  USt-Id: DE279960836
Tel.: +49 (0) 160 97590858
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