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Subject: Re: [OMPI users] Number of processes and spawn
From: Ralph Castain (rhc_at_[hidden])
Date: 2010-02-27 09:57:11


Okay, thanks. It's the same problem as the other person encountered. Basically, it looks to OMPI as if you are launching > 128 independent app contexts, and our arrays were limited to 128.

He has provided a patch that I'll review (couple of things I'd rather change) and then apply to our developer's trunk. I would expect it to migrate over to the 1.4 release series at some point (can't guarantee which one).

On Feb 27, 2010, at 6:47 AM, Federico Golfrè Andreasi wrote:

> Hi,
>
> the program is executed as one application on 129 cpus defined by the hostfile.
> Than rank 0, inside the code, execute another program with 129 cpus, with a one-to-one relation, rank0 of the spawined process runs on the same host of rank0 of the spawning one and so on...
> Excuting the spawning program does not give any problem,
> but in the moment of spawning (with more than 128 cpus) it holds.
>
> Thank you!
>
> Federico
>
>
>
>
> 2010/2/27 Ralph Castain <rhc_at_[hidden]>
> Since another user was doing something that caused a similar problem, perhaps we are missing a key piece of info here. Are you launching one app_context across 128 nodes? Or are you launching 128 app_contexts, each on a separate node?
>
>
> On Feb 26, 2010, at 10:23 AM, Federico Golfrè Andreasi wrote:
>
>> I'm doing some tests and it seems that is not able to do a spawn multiple with more than 128 nodes.
>>
>> It just hold, with no error message.
>>
>> What do you think? What can I try to understand the problem.
>>
>> Thanks,
>>
>> Federico
>>
>>
>>
>>
>> 2010/2/26 Ralph Castain <rhc_at_[hidden]>
>> No known limitations of which we are aware...the variables are all set to int32_t, so INT32_MAX would be the only limit I can imagine. In which case, you'll run out of memory long before you hit it.
>>
>>
>> 2010/2/26 Federico Golfrè Andreasi <federico.golfre_at_[hidden]>
>> HI !
>>
>> have you ever did some analysis to understand if there is a limitation in the number of nodes usable with OpenMPI-v1.4 ?
>> Using also the functions MPI_Comm_spawn o MPI_Comm_spawn_multiple.
>>
>> Thanks,
>> Federico
>>
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