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Subject: Re: [OMPI users] How to specify hosts for MPI_Comm_spawn
From: Mark Borgerding (markb_at_[hidden])
Date: 2008-07-29 11:08:59


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.
>>
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>
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