Introduction

Running FORTRAN 90 programs on the cluster is similar to running any other serial job. Make sure you've read the tutorial for C programs first, to understand the basics.

Serial Example

Let's try to compile this simple Fortran 90 program:

program HelloWorldF90
    write(*,*) "Greetings, denizens of planet Earth!"
end program HelloWorldF90

Download: ../code-2010/hello_serial-f90/hello_serial.f90

To compile this using GCC and create the executable helloworld-f90-gcc, type:

[araim1@tara-fe1 hello_serial-f90]$ gfortran hello_serial.f90 -o hello_serial-f90-gcc
[araim1@tara-fe1 hello_serial-f90]$

Alternatively, to compile using PGI Fortran and create the executable helloworld-f90-pgi, type

[araim1@tara-fe1 hello_serial-f90]$ pgf90 hello_serial.f90 -o hello_serial-f90-pgi
[araim1@tara-fe1 hello_serial-f90]$

Running this program should produce this output:

[araim1@tara-fe1 hello_serial-f90]$ ./helloworld-f90-gcc
Greetings, denizens of planet Earth!
[araim1@tara-fe1 hello_serial-f90]$ ./helloworld-f90-pgi
Greetings, denizens of planet Earth!
[araim1@tara-fe1 hello_serial-f90]$

Parallel Example

We'll assume that you already know the fundamentals of MPI execution from the C tutorial. Now let's create the following program:

program hello_parallel

  ! Include the MPI library definitons:
  include 'mpif.h'

  integer numtasks, rank, ierr, rc, len, i
  character*(MPI_MAX_PROCESSOR_NAME) name

  ! Initialize the MPI library:
  call MPI_INIT(ierr)
  if (ierr .ne. MPI_SUCCESS) then
     print *,'Error starting MPI program. Terminating.'
     call MPI_ABORT(MPI_COMM_WORLD, rc, ierr)
  end if

  ! Get the number of processors this job is using:
  call MPI_COMM_SIZE(MPI_COMM_WORLD, numtasks, ierr)

  ! Get the rank of the processor this thread is running on.  (Each
  ! processor has a unique rank.)
  call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr)

  ! Get the name of this processor (usually the hostname)
  call MPI_GET_PROCESSOR_NAME(name, len, ierr)
  if (ierr .ne. MPI_SUCCESS) then
     print *,'Error getting processor name. Terminating.'
     call MPI_ABORT(MPI_COMM_WORLD, rc, ierr)
  end if

  print "('hello_parallel.f: Number of tasks=',I3,' My rank=',I3,' My name=',A,'')",&
       numtasks, rank, trim(name)

  ! Tell the MPI library to release all resources it is using:
  call MPI_FINALIZE(ierr)

end program hello_parallel

Download: ../code-2010/hello_parallel-f90/hello_parallel.f90

Now we can compile the program with

[araim1@tara-fe1 hello_parallel-f90]$ mpif90 hello_parallel.f90 -o hello_parallel

The same compilation command should work even if you've changed the switcher to use a different MPI implementation and compiler. Running the compiled program is now exactly the same as running a C MPI program.