Q-Logic IB6054601-00 D Benutzerhandbuch

3 – Using InfiniPath MPI
Getting Started with MPI

3-2

IB6054601-00 D

Q

These examples assume that:

■

 Your cluster administrator has properly installed InfiniPath MPI and the 
PathScale compilers. 

■

 Your cluster’s policy allows you to use the 

mpirun

 script directly, without having 

to submit the job to a batch queuing system. 

■

 You or your administrator has properly set up your 

ssh

 keys and associated files 

on your cluster. See 

 and 

 for details on 

ssh

 

administration.

To begin, copy the examples to your working directory:

$ cp /usr/share/mpich/examples/basic/* .

Next, create an MPI hosts file in the same working directory. It contains the host 
names of the nodes in your cluster on which you want to run the examples, with 
one host name per line. Name this file 

mpihosts

. The contents can be in the 

following format:

hostname1

hostname2

...

There is more information on the 

mpihosts

 file in 

InfiniPath MPI uses some shell scripts to find the appropriate include files and 
libraries for each supported language. Use the script 

mpicc

 to compile an MPI 

program in C and the script 

mpirun

 to execute it.

The supplied example program 

cpi.c

 computes an approximation to pi. First, 

compile it to an executable named 

cpi

. 

$ mpicc -o cpi cpi.c

mpicc

, by default, runs the PathScale pathcc or gcc compiler, and is used for 

both compiling and linking, exactly as you'd use the 

pathcc

 command.

On ppc64 systems, gcc is the default compiler. For information on using 
other compilers, see 

Then, run it with several different specifications for the number of processes: 

$ mpirun -np 2 -m mpihosts ./cpi

Process 0 on hostname1

Process 1 on hostname2

pi is approximately 3.1416009869231241, 

Error is 0.0000083333333309

wall clock time = 0.000149