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Subject: Re: [OMPI users] calling a customized MPI_Allreduce with MPI_PACKED datatype
From: jody (jody.xha_at_[hidden])
Date: 2011-02-06 16:44:29


Hi Massimo

Just to make sure: usually the MPI_ERR_TUNCATE error is caused by
buffer sizes that are too small.
Can you verify that the buffers you are using are large enough to
hold the data they should receive?

Jody

On Sat, Feb 5, 2011 at 6:37 PM, Massimo Cafaro
<massimo.cafaro_at_[hidden]> wrote:
> Dear all,
>
> in one of my C codes developed using Open MPI v1.4.3 I need to call MPI_Allreduce() passing as sendbuf and recvbuf arguments two MPI_PACKED arrays. The reduction requires my own MPI_User_function that needs to  MPI_Unpack() its first and second argument, process them and finally MPI_Pack() the result in the second argument.
>
> I need to use MPI_Pack/MPI_Unpack because I am not able to create a derived datatype, since many data I need to send are dynamically allocated.
> However, the code fails at runtime with the following message:
>
> An error occurred in MPI_Unpack
> on communicator MPI_COMM_WORLD
> MPI_ERR_TRUNCATE: message truncated
> MPI_ERRORS_ARE_FATAL (your MPI job will now abort)
>
> I have verified that, after unpacking the data in my own reduction function, all of the data are wrong.
> Is this possible in MPI? I did not find anything on the "MPI reference Volume 1" and "Using MPI"  that prevents this. This should just require using as datatype MPI_PACKED in MPI_Allreduce() . However, searching on the web I did not find any examples.
>
> Thank you in advance for any clue/suggestions/source code examples.
> This is driving me crazy now ;-(
>
> Massimo Cafaro
>
>
> -
>
> *******************************************************************************************************
>
>  Massimo Cafaro, Ph.D.                               Additional affiliations:
>  Assistant Professor                                      Euro-Mediterranean Centre for Climate Change
>  Dept. of Engineering for Innovation          SPACI Consortium
>  University of Salento, Lecce, Italy             E-mail massimo.cafaro_at_[hidden]
>  Via per Monteroni                                                     massimo.cafaro_at_[hidden]
>  73100 Lecce, Italy                                                                     cafaro_at_[hidden]
>  Voice/Fax  +39 0832 297371                                                     cafaro_at_[hidden]
>  Web     http://sara.unisalento.it/~cafaro
>
>
> *******************************************************************************************************
>
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