Working with Fortran

The tutorial assumes you have already worked through the Execute a Job Tutorial. Therefore, the instructions here are abbreviated but will follow the same format so you may easily consult the extended tutorial.

Table of Contents

📝 Note: Do not execute jobs on the login nodes; only use the login nodes to access your compute nodes. Processor-intensive, memory-intensive, or otherwise disruptive processes running on login nodes will be killed without warning.

Step 1: Access the Onyx HPC

  1. Open a Bash terminal (or MobaXterm for Windows users).

  2. Execute ssh [email protected].

  3. When prompted, enter your password.

Step 2: Create an sbatch Script

Example sbatch Script

Here is an example sbatch script for running a batch job on an HPC like Onyx.

#SBATCH -n 16
#SBATCH -o test_%A.out
#SBATCH --error test_%A.err
#SBATCH --mail-type ALL
module purge
module load gnu/5.4.0
module load openmpi
module list
mpirun hello_world_f

sbatch Procedure

  1. Use nano or Vim (we use Vim here) to create and edit your sbatch script.

    vim slurm_f90_example.job
  2. Create your sbatch script within Vim by typing i for insert mode or paste the contents of your sbatch script into Vim.

  3. Save your file by typing :wq! and return to the Bash shell.

Step 3: Compile the Fortran Program from Source

MPI Hello World Source Code

program helloworld
use mpi
integer ierr, numprocs, procid
call MPI_INIT(ierr)
call MPI_COMM_RANK(MPI_COMM_WORLD, procid, ierr)
call MPI_COMM_SIZE(MPI_COMM_WORLD, numprocs, ierr)
print *, "Hello world! I am process ", procid, "out of", numprocs, "!"
call MPI_FINALIZE(ierr)

Fortran Procedure

  1. Use Vim (vim) to create your Fortran source file.

    vim hello_world.f90
  2. Save your file and return to the Bash shell.

  3. Load the MPI compiler using the openmpi module.

    module load openmpi
  4. Compile the Fortran source into a binary executable file.

    mpifort -o hello_world_f hello_world.f90
  5. Use ls -al to verify the presence of the hello_world_f binary in your working directory.

Step 4: Run the Job

  1. Before proceeding, ensure that you are still in your working directory (using pwd) and that you still have the PE-gnu module loaded (using module list).

    • We need to be in the same path/directory as our sbatch script and our Fortran binary. Use ls -al to confirm their presence.

  2. Use sbatch to schedule your batch job in the queue.

    sbatch slurm_f90_example.job

    This command will automatically queue your job using slurm and produce a job number. You can check the status of your job at any time with the squeue command.

    squeue --job <jobnumber>

    You can also stop your job at any time with the scancel command.

    scancel --job <jobnumber>
  3. View your results. You can view the contents of these files using the less command followed by the file name.

    less test_<jobnumber>.out

    Your output should look something like this (the output is truncated.):

    Hello world! I am process 3 out of 20 !
    Hello world! I am process 0 out of 20 !
    Hello world! I am process 1 out of 20 !
    Hello world! I am process 7 out of 20 !
    Hello world! I am process 8 out of 20 !
    Hello world! I am process 2 out of 20 !
    Hello world! I am process 6 out of 20 !
    Hello world! I am process 11 out of 20 !
  4. Download your results (using the scp command or an SFTP client) or move them to persistent storage. See our moving data section for help.

Additional Examples