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Subject: Re: [OMPI users] How to specify hosts for MPI_Comm_spawn
From: Ralph Castain (rhc_at_[hidden])
Date: 2008-07-29 11:19:49


Are the hosts where you want the children to go in your -hostfile
file? All of the hosts you intend to use have to be in that file, even
if they don't get used until the comm_spawn.

On Jul 29, 2008, at 9:08 AM, Mark Borgerding wrote:

> I've tried lots of different values for the "host" key in the info
> handle.
> I've tried hardcoding the hostname+ip entries in the /etc/hosts file
> -- no luck. I cannot get my MPI_Comm_spawn children to go anywhere
> else on the network.
>
> mpiexec can start groups on the other machines just fine. It seems
> like there is some initialization that is done by orterun but not by
> MPI_Comm_spawn.
>
> Is there a document that describes how the default process
> management works?
> I do not have infiniband, myrinet or any specialized rte, just ssh.
> All the machines are CentOS 5.2 (openmpi 1.2.5)
>
>
> -- Mark
>
> Ralph Castain wrote:
>> The string "localhost" may not be recognized in the 1.2 series for
>> comm_spawn. Do a "hostname" and use that string instead - should
>> work.
>>
>> Ralph
>>
>> On Jul 28, 2008, at 10:38 AM, Mark Borgerding wrote:
>>
>>> When I add the info parameter in MPI_Comm_spawn, I get the error
>>> "Some of the requested hosts are not included in the current
>>> allocation for the application:
>>> [...]
>>> Verify that you have mapped the allocated resources properly using
>>> the
>>> --host specification."
>>>
>>> Here is a snippet of my code that causes the error:
>>>
>>> MPI_Info info;
>>> MPI_Info_create( &info );
>>> MPI_Info_set(info,"host","localhost");
>>> MPI_Comm_spawn( cmd , MPI_ARGV_NULL , nkids , info , 0 ,
>>> MPI_COMM_SELF , &kid , errs );
>>>
>>>
>>>
>>>
>>> Mark Borgerding wrote:
>>>> Thanks, I don't know how I missed that. Perhaps I got thrown off by
>>>> "Portable programs not requiring detailed control over process
>>>> locations should use MPI_INFO_NULL."
>>>>
>>>> If there were a computing equivalent of Maslow's Hierarchy of
>>>> Needs, functioning would be more fundamental than portability :)
>>>>
>>>> -- Mark
>>>>
>>>>
>>>> Ralph Castain wrote:
>>>>> Take a look at the man page for MPI_Comm_spawn. It should
>>>>> explain that you need to create an MPI_Info key that has the key
>>>>> of "host" and a value that contains a comma-delimited list of
>>>>> hosts to be used for the child processes.
>>>>>
>>>>> Hope that helps
>>>>> Ralph
>>>>>
>>>>> On Jul 28, 2008, at 8:54 AM, Mark Borgerding wrote:
>>>>>
>>>>>> How does openmpi decide which hosts are used with
>>>>>> MPI_Comm_spawn? All the docs I've found talk about specifying
>>>>>> hosts on the mpiexec/mpirun command and so are not applicable.
>>>>>> I am unable to spawn on anything but localhost (which makes for
>>>>>> a pretty uninteresting cluster).
>>>>>>
>>>>>> When I run
>>>>>> ompi_info --param rds hostfile
>>>>>> It reports MCA rds: parameter
>>>>>> "rds_hostfile_path" (current value: "/usr/lib/openmpi/1.2.5-gcc/
>>>>>> etc/openmpi-default-hostfile")
>>>>>> I tried changing that file but it has no effect.
>>>>>>
>>>>>>
>>>>>> I am using
>>>>>> openmpi 1.2.5
>>>>>> CentOS 5.2
>>>>>> ethernet TCP
>>>>>>
>>>>>>
>>>>>> -- Mark
>>>>>> _______________________________________________
>>>>>> users mailing list
>>>>>> users_at_[hidden]
>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>>>
>>>>> _______________________________________________
>>>>> users mailing list
>>>>> users_at_[hidden]
>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>>>
>>>>
>>>
>>>
>>> --
>>> Mark Borgerding
>>> 3dB Labs, Inc
>>> Innovate. Develop. Deliver.
>>>
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
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