[mpich-discuss] How to determine if a program is not started with mpiexec

[James Dinan]

That's interesting.  The example in 10.3.5 also suggests that 
UNIVERSE_SIZE should be used for this purpose.  I wrote a little test 
that suggests the value may not be helpful:

$ mpiexec -n 2 ./a.out
0: UNIVERSE_SIZE = 1
1: UNIVERSE_SIZE = 1

When run with the MPICH2 trunk on my 4-core laptop.

  ~Jim.

On 10/28/11 3:06 PM, Jeff Hammond wrote:
> Shouldn't the MPI_UNIVERSE_SIZE attribute of MPI_COMM_WORLD provide a
> useful way to check if MPI_COMM_SPAWN can be used to start new
> processes?
>
> See the very last bullet of MPI 2.2 Section 10.2.2 for the text to
> which I refer.
>
> Jeff
>
> On Fri, Oct 28, 2011 at 1:25 PM, Darius Buntinas<buntinas at mcs.anl.gov>  wrote:
>>
>> On Oct 28, 2011, at 1:01 PM, Jonathan Bishop wrote:
>>
>>> Hi,
>>>
>>> I would like to be able to detect when a program is not started with mpiexec. This is to prevent MPI_Comm_spawn from failing.
>>
>> There's no portable way to determine if it's been started with mpiexec.  You could look for environment variables set by mpiexec.  A portable way would be to set the error handler on a communicator to MPI_ERRORS_RETURN, then try to do a spawn and check the return value.
>>
>>> Or is there a way to make MPI_Comm_spawn work in the case where a program is simply run by running its exec?
>>
>> This depends on the MPI implementation, but currently MPICH doesn't support this.
>>
>> -d
>>
>>
>>> Jon
>>>
>>>
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>
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