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.
--
Jeff Squyres
Cisco Systems
