Re: [Libmesh-users] parallel performance

[Kirk, B. (JSC-EG311) <ben...@na...>]

There is a lot of parallel communication buried in there too (it performs a parallel binsort), so the same root cause may be to blame.

-Ben


----- Original Message -----
From: Yujie <rec...@gm...>
To: Kirk, Benjamin (JSC-EG311)
Cc: lib...@li... <lib...@li...>
Sent: Mon Jan 18 15:25:41 2010
Subject: Re: [Libmesh-users] parallel performance

Dear Ben,

Thank you for your reply. I need to check the machine interconnect. My
problem is two coupled elliptic-typed PDEs. According to your advice, the
unstable time cost of Probe() is most likely from the hardware. However, how
about the find_global_indices()? Generally, this function took almost the
entire time. Thanks a lot.

Regards,
Yujie

On Mon, Jan 18, 2010 at 3:18 PM, Kirk, Benjamin (JSC-EG311) <
ben...@na...> wrote:

> What is the machine interconnect?
>
> What is the problem you are running?
>
> Probe() indicates the code is waiting on an mpi message to arrive or
> complete.  If the network is poor or the cluster is unevenly loaded this
> could cause what appear (to me) to be very long probes and the
> unrepeatability you report.
>
> For a well tuned system with no job contention the probes should take
> essentially 0 time - the code is structured so that the messages are likely
> ready when the probe is issued.
>
> -Ben
>
>
> ----- Original Message -----
> From: Yujie <rec...@gm...>
> To: lib...@li... <
> lib...@li...>
> Sent: Mon Jan 18 12:48:30 2010
> Subject: [Libmesh-users] parallel performance
>
> Dear Libmesh Developers,
>
> Recently, I use the new SVN libmesh (downloaded in about November) for my
> application. When I tried to increase the number of CPU to observe the
> parallel performance with adaptive mesh evolution. I find that Functions:
> MeshCommunication: find_global_indices( ) and Parallel:probe( ) spend most
> of the whole cost time. Further, the cost time is not stable. For example,
>
> CPUs total time   time of find_global_indices() time of probe()
>  2         6473.0            5389.0                            0.0767
>  3         5337.0            4843.0                            12.73
>  4         1341.0            921.0                              18.64
>  5         2959.0          2299.0                              179.7
>  6         3071.0          622.4                                2035.4
>
> I am using X86_64 Cluster. Could you give me some advice? Thanks a lot.
>
> Regards,
> Yujie
>
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