[Beowulf] MPI & ScaLAPACK: error in MPI_Comm_size: Invalid communicator

Gabb, Henry henry.gabb at intel.com
Tue Oct 19 14:21:31 PDT 2004

Hi Clint,
The "Null Comm pointer" error that you're seeing is almost always due to
a header mismatch. I don't think Intel Cluster MKL 7.0 supports MPICH2
yet. According to the Intel Cluster MKL system requirements
MPICH-1.2.5 is supported. MPICH-1.2.6 should work too. You might post a
question to the Intel MKL forum (http://softwareforums.intel.com/ids)
about MPICH2 support.

I did a quick test of your program on one of my clusters and it ran fine
(after fixing the typo in the nocol=3 statement):

[henry at castor1 cmkl-test]$ /opt/mpich-1.2.6-gcc/bin/mpif77 -o example
example.f \
-lmkl_scalapack \
                             -lmkl_blacsF77init_gnu -lmkl_blacs
-lmkl_blacsF77init_gnu \
                             -lmkl_lapack -lmkl -lguide -lpthread
[henry at castor1 cmkl-test]$ /opt/mpich-1.2.6-gcc/bin/mpirun -n 6
[henry at castor1 cmkl-test]$ 

I used a GNU-built MPICH-1.2.6 because I didn't have an Intel-ready
MPICH installation handy.

Best regards,

Henry Gabb
Intel Parallel and Distributed Solutions Division

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