[mpich-discuss] MPI_TYPE_MAX limit using MPT

[Michael Raymond]

  That's correct.  In MPT every element of a complex type like a struct
or indexed type ends up taking up a type in the global table.  There are
good speed reasons for this but the downside is that you sometimes need
to preallocate a ton of space for datatypes.  This is remedied to some
extent in MPT 2.03.  If you have any more questions about MPT you can
contact me directly.

Wei-keng Liao wrote:
> Hi, Max,
> 
> I am cc this to mpich discuss group. Hope people there can provide more thorough
> answers. 
> 
> I have not run jobs on a SGI machine for a long time, but I remember I have to
> increase MPI_TYPE_MAX in order to run an MPI-IO job. In collective I/O, ROMIO
> uses MPI derived data type for exchanging I/O requests among processes. So,
> the more processes a job runs, the bigger number MPI_TYPE_MAX should be set.
> 
> Wei-keng
> 
> On Oct 6, 2010, at 11:29 AM, Maxwell Kelley wrote:
> 
>> Hello,
>>
>> When running some I/O tests using MPT 1.25, I get the error
>>
>> MPI has run out of internal datatype entries.
>> Please set the environment variable MPI_TYPE_MAX for additional space.
>> The current value of MPI_TYPE_MAX is 8192
>>
>> Is this normal?  Setting MPI_TYPE_MAX to 65536 simply allowed more I/O to be performed before the error appears. The limit is reached more quickly using more processors.  Assuming that this is a case of types not being freed after use, should I just set this limit high enough that it will never be exceeded during a 12-hour batch job?
>>
>> -Max
>>
> 
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-- 
Michael A. Raymond
Message Passing Toolkit Team
Silicon Graphics Inc
(651) 683-3434