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Subject: Re: [OMPI users] MPI_ERR_TRUNCATE with MPI_Allreduce() error, but only sometimes...
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-05-20 07:28:28


Sorry for the super-late reply. :-\

Yes, ERR_TRUNCATE means that the receiver didn't have a large enough buffer.

Have you tried upgrading to a newer version of Open MPI? 1.4.3 is the current stable release (I have a very dim and not guaranteed to be correct recollection that we fixed something in the internals of collectives somewhere with regards to ERR_TRUNCATE...?).

On Apr 25, 2011, at 4:44 PM, Wei Hao wrote:

> Hi:
>
> I'm running openmpi 1.2.8. I'm working on a project where one part involves communicating an integer, representing the number of data points I'm keeping track of, to all the processors. The line is simple:
>
> MPI_Allreduce(&np,&geo_N,1,MPI_INT,MPI_MAX,MPI_COMM_WORLD);
>
> where np and geo_N are integers, np is the result of a local calculation, and geo_N has been declared on all the processors. geo_N is nondecreasing. This line works the first time I call it (geo_N goes from 0 to some other integer), but if I call it later in the program, I get the following error:
>
>
> [woodhen-039:26189] *** An error occurred in MPI_Allreduce
> [woodhen-039:26189] *** on communicator MPI_COMM_WORLD
> [woodhen-039:26189] *** MPI_ERR_TRUNCATE: message truncated
> [woodhen-039:26189] *** MPI_ERRORS_ARE_FATAL (goodbye)
>
>
> As I understand it, MPI_ERR_TRUNCATE means that the output buffer is too small, but I'm not sure where I've made a mistake. It's particularly frustrating because it seems to work fine the first time. Does anyone have any thoughts?
>
> Thanks
> Wei
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-- 
Jeff Squyres
jsquyres_at_[hidden]
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