QLogic OFED+ Host Software User Guide, Rev. B

4–Running QLogic MPI on QLogic Adapters
Getting Started with MPI
Generally, mpirun tries to distribute the specified number of processes evenly
among the nodes listed in the mpihosts file. However, if the number of
processes exceeds the number of nodes listed in the mpihosts file, then some
nodes will be assigned more than one instance of the program.
When you run the program several times with the same value of the -np
parameter, the output lines may display in different orders. This is because they
are issued by independent asynchronous processes, so their order is
non-deterministic.
Details on other ways of specifying the mpihosts file are provided in “mpihosts
File Details” on page 4-15.
More information on the mpirun options are in “Using mpirun” on page 4-16 and
Appendix A mpirun Options Summary. “Process Allocation” on page 4-11
explains how processes are allocated by using hardware and software contexts.
Examples Using Other Programming Languages
This section gives similar examples for computing pi for Fortran 77 and
Fortran 90. Fortran 95 usage is similar to Fortran 90. The C++ example uses the
traditional “Hello, World” program. All programs are located in the same directory.
fpi.f is a Fortran 77 program that computes pi in a way similar to cpi.c.
Compile and link, and run it as follows:
$ mpif77 -o fpi fpi.f
$ mpirun -np 2 -m mpihosts ./fpi
pi3f90.f90 is a Fortran 90 program that does the same computation. Compile
and link, and run it as follows:
$ mpif90 -o pi3f90 pi3f90.f90
$ mpirun -np 2 -m mpihosts ./pi3f90
The C++ program hello++.cc is a parallel processing version of the traditional
“Hello, World” program. Notice that this version makes use of the external C
bindings of the MPI functions if the C++ bindings are not present.
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