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Subject: Re: [OMPI devel] MPI_REAL16
From: David Robertson (robertson_at_[hidden])
Date: 2009-06-20 18:28:13


Hi Jeff,

Bellow is the reply I got from Intel and it seemed to work:

David,

I received your issue. There isn't an equivalent type to Real*16 in icc
without the -Qoption,cpp,--extended_float_types option because there is
no runtime library support for quad precision.

Your test case has a bug in the Fortran code. Your literal is not QuAD
precision. You need to do the assignement as follows:

foo = 1.1_16

After making this change you still see fortran equal and a and b will
also be equal.

Can you also request the owner of the code online make this correction?

Please let me know if you have additional questions.

Regards,

Elizabeth S.
Intel Developer Support

Jeff Squyres wrote:
> Greetings David.
>
> I think we should have a more explicit note about MPI_REAL16 support in
> the README.
>
> This issue has come up before; see
> https://svn.open-mpi.org/trac/ompi/ticket/1603.
>
> If you read through that ticket, you'll see that I was unable to find a
> C equivalent type for REAL*16 with the Intel compilers. This is what
> blocked us from making that work. :-\ But then again, I haven't tried
> the test codes on that ticket with the Intel 11.0 compilers to see what
> would happen (last tests were with 10.something). It *seems* to be a
> compiler issue, but I confess that we never had a high enough priority
> to follow through and figure it out completely.
>
> If you have an Intel support contract, you might want to take some of
> the final observations on #1603 (e.g., the test codes I put near the
> end) and see what Intel has to say about it. Perhaps we're doing
> something wrong...?
>
> I hate to pass the buck here, but I unfortunately have a whole pile of
> higher-priority items that I need to work on...
>
>
>
> On Jun 19, 2009, at 1:32 PM, David Robertson wrote:
>
>> Hi all,
>>
>> I have compiled Open MPI 1.3.2 with Intel Fortran and C/C++ 11.0
>> compilers. Fortran Real*16 seems to be working except for MPI_Allreduce.
>> I have attached a simple program to show what I mean. I am not an MPI
>> programmer but I work for one and he actually wrote the attached
>> program. The program sets a variable to 1 on all processes then sums.
>>
>> Running with real*8 (comment #define REAL16 in quad_test.F) produces the
>> expected results:
>>
>> Number of Nodes = 4
>>
>> ALLREDUCE sum = 4.00000000000000
>> ALLGATHER sum = 4.00000000000000
>> ISEND/IRECV sum = 4.00000000000000
>>
>> Node = 0 Value = 1.00000000000000
>> Node = 2 Value = 1.00000000000000
>> Node = 3 Value = 1.00000000000000
>> Node = 1 Value = 1.00000000000000
>>
>> Running with real*16 produces the following:
>>
>> Number of Nodes = 4
>>
>> ALLREDUCE sum = 1.00000000000000000000000000000000
>> ALLGATHER sum = 4.00000000000000000000000000000000
>> ISEND/IRECV sum = 4.00000000000000000000000000000000
>> Node = 0 Value = 1.00000000000000000000000000000000
>> Node = 1 Value = 1.00000000000000000000000000000000
>> Node = 2 Value = 1.00000000000000000000000000000000
>> Node = 3 Value = 1.00000000000000000000000000000000
>>
>> As I mentioned, I'm not a parallel programmer but I would expect the
>> similar results from identical operations on real*8 and real*16
>> variables.
>>
>> NOTE: I get the same behavior with MPICH and MPICH2.
>>
>
>