[mpich-discuss] How to find out maximum number of processes in mpiexec configuration

[Yauheni Zelenko]

Hi, Pavan!

I know, that resource managers queuing will work, but this job is already done in Hydra. I think will be good idea to make this information available to clients too. It'll definitely simplify client code.

Eugene.
________________________________________
From: Pavan Balaji [balaji at mcs.anl.gov]
Sent: Wednesday, January 26, 2011 8:22 PM
To: mpich-discuss at mcs.anl.gov
Cc: Yauheni Zelenko
Subject: Re: [mpich-discuss] How to find out maximum number of processes        in mpiexec configuration

Hi,

Sounds like you are trying to find the number of cores in the system?
You will need to query the resource manager, such as PBS, for this
information. You can't get this from mpiexec.

  -- Pavan

On 01/26/2011 03:54 PM, Yauheni Zelenko wrote:
> Hi, Rajeev!
>
> Thank you for suggestion!
>
> However I grepped through MPI 1.3.1 code and see that this variable will be initialized only from command line, but not from combination of -host/host list file and -ppn (in Hydra), what may serve my purpose.
>
> Eugene.
> ________________________________________
> From: mpich-discuss-bounces at mcs.anl.gov [mpich-discuss-bounces at mcs.anl.gov] On Behalf Of Rajeev Thakur [thakur at mcs.anl.gov]
> Sent: Wednesday, January 26, 2011 1:23 PM
> To: mpich-discuss at mcs.anl.gov
> Subject: Re: [mpich-discuss] How to find out maximum number of processes in     mpiexec configuration
>
> mpiexec will let you run as many processes as many as you want -- to the extent that the OS can run that many processes.
>
> For dynamic processes (Comm_spawn), MPI defines an attribute on MPI_COMM_WORLD called MPI_UNIVERSE_SIZE, whose value indicates how many processes can be started with Comm_spawn. See the first line on pg 308 in the MPI 2.2 standard.
>
> Rajeev
>
>
> On Jan 25, 2011, at 5:58 PM, Yauheni Zelenko wrote:
>
>> Hi!
>>
>> Is there any way to find out how much MPI processes are allowed to run by current mpiexec configuration inside MPI application?
>>
>> I want to replicate mpiexec default behavior (when -n is not specified and processes are started on all available hosts) with MPI_Comm_spawn() when only single process starts from mpiexec (-n 1) and all other processes will be spawned from it later.
>>
>> Eugene.
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>
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--
Pavan Balaji
http://www.mcs.anl.gov/~balaji