HELLO
The Hello World Program, OpenMP version

HELLO is a simple program that says "Hello", but also demonstrates a few simple things about OpenMP programs, including

• How you get the "include" file.
• How you measure wall clock time.
• How you find out how many processors are available.
• How you find out which thread you are in a parallel section.
• How you find out how many threads are available in a parallel section.
• How you set the number of threads.

To use the program, you will also need to figure out the appropriate compiler switches to use, and how to set the enviroment variable OMP_NUM_THREADS to the number of threads you want.

Source Code:

To run the HELLO program, you first need to copy one of these source code files, compile it using the appropriate compiler switches, and be sure to name the executable hello.

• hello.c, the C source code.
• hello.cc, the C++ source code.
• hello.f, the FORTRAN77 source code.
• hello.f90, the FORTRAN90 source code.

Script for Local Execution:

If you have created an OpenMP executable from the hello source code, and called it hello, then you can run the following BASH shell script to execute the program requesting 1, 2, 4 and 8 threads, using the command

        bash hello_local.sh
      

• hello_local.sh, runs the program locally.
• hello_local_output.txt, the output file.

Script for Batch Execution on the FSU HPC:

Once you have made an OpenMP executable from the hello source code, copy the following script file to the same directory, and issue the command msub hello.sh. That submits a request to have the executable program run on 1, 2 and 4 processors. You can type showq to see if the request has started yet. When the program has completed, the output should show up in the file "hello_batch_output.txt".

• hello_batch.sh, a script to submit to the batch system.
• hello_batch_output.txt, the output file.

You can go up one level to the OpenMP page.