[MITgcm-support] MPI problem on Archer (CRAY XC30)

[Chris Hill]

Hi David and Jean-Michel,

 I am unsure why generate_tag doesn’t just do "iarg1+iarg2", but
lets try Jean-Michels’s fix. Not sure who introduced the funky
hash stuff in the first place. My recollection is that “iarg1+iarg2”
should be all that are needed, but that code was a long time ago!

Chris

On Mon, Oct 20, 2014 at 10:29 PM, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:
> Hi David,
>
> Could you try to replace the original
>  pkg/compon_communic/generate_tag.F
> with the modified "generate_tag.F" routine (attached to this email)
> and check that it works ?
>
> Cheers,
> Jean-Michel
>
> On Mon, Oct 20, 2014 at 03:14:51PM +0100, David Ferreira wrote:
>> Hi all,
>> I'm having a problem running the coupled model on Archer.
>> The Archer support team discovered the following problem:
>>
>> ##########
>> ...
>> ---
>> Rank 0 [Tue Oct  7 22:44:10 2014] [c7-0c1s12n2] Fatal error in
>> MPI_Recv: Invalid
>> tag, error stack:
>> MPI_Recv(192): MPI_Recv(buf=0x7fffffff8000, count=1024, MPI_INTEGER,
>> src=1, tag=9862928,
>>  comm=0x84000004, status=0x7fffffff7df0) failed
>> MPI_Recv(113): Invalid tag, value is 9862928
>> ---
>>
>> The maximum allowed value for the "tag" in MPI messages on Cray XC30 systems
>> is 4194303, which explains the error message
>>
>> MPI_Recv(113): Invalid tag, value is 9862928
>>
>> The MPI standard only requires that the maximum tag value is not less than
>> 32767 (so Cray MPI is compliant). The maximum can be larger, and can
>> be found
>> using the MPI_Get_attr enquiry function. Your program should
>> retrieve this value
>> and ensure that any tags it specifies are no larger.
>>
>> ##########
>>
>> I have absolutely no clue how to tell the model to choose MPI tags
>> which are below 4194303.
>> A bit of googling on MPI_Get_attr led me to some very obscure pages.
>>
>> Any help is welcome.
>> Cheers,
>> david
>>
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