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MPI_GATHERV hangs for non-root process sending zero data

Christopher
Beginner
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I am using Intel OneAPI version 2021.3.0 20210609.

 

When calling MPI_GATHERV, a non-root process sending zero information does not exit the MPI_GATHERV call (i.e. it hangs). All other processes complete, and the root process gathers all the data correctly.

 

Note that the root process always has zero information in it's send buffer as it is a manager process. That is why I explicitly state above this issue is only related to a non-root process sending zero information. 

 

Wrapping the call to MPI_GATHERV with an if statement that sends `MPI_BOTTOM` in as an argument seems to fix the issue. But I don't understand why this is necessary:

 

 

 if (self%is_manager() .OR. dim1_size .gt. 0) then
    call MPI_GatherV(gather_variable,int(dim1_size,kind=MPI_INTEGER_KIND),datatype, &
     gathered_result,int(dim1_size_gathered,kind=MPI_INTEGER_KIND),displs,datatype, &
            self%manager_id,self%comm,ierror)
 else
    call MPI_GatherV(MPI_BOTTOM,int(dim1_size,kind=MPI_INTEGER_KIND),datatype, &
            gathered_result,int(dim1_size_gathered,kind=MPI_INTEGER_KIND),displs,datatype, &
            self%manager_id,self%comm,ierror)
 end if

 

 

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VarshaS_Intel
Moderator
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Hi,


Thanks for reaching out to us.


Could you please provide the system environment details?


And also, could you please provide the complete sample reproducer code so that we can investigate more on your issue?


Thanks & Regards

Varsha


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VarshaS_Intel
Moderator
749 Views

Hi,


We haven't heard back from you. Could you please provide the details mentioned in the previous post?


Thanks & Regards

Varsha


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VarshaS_Intel
Moderator
720 Views

Hi,


We have not heard back from you. This thread will no longer be monitored by Intel. If you need further assistance, please post a new question.


Thanks & Regards

Varsha


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