Coarray Fortran on LRZ HPC systems
How to compile and run Coarray Fortran programs on LRZ HPC systems
Availability on LRZ HPC systems
Coarrays are supported by two compilers on the LRZ HPC systems:
- Intel's Fortran compiler (ifort) from version 12.0 upwards (x86_64 systems only)
- The g95 compiler from 0.92 upwards. It requires a commercial add-on to actually run the binaries in parallel, comprised of a special version of the run time library and a parallel console. Alternatively, a shared memory implementation is also available.
Please load the environment module caf, which gives you one of the coarray environments:
module load caf
By default, the Intel compiler's run time is added to the existing fortran/intel module, which must be loaded with a version number of 12.0 or greater
module load caf/g95_cocon
will load the coarray console version, and
module load caf/g95
the shared memory version.
Building and running programs
A simple (and trivial) example program
write(*, '(''Hello from image '',i0, '' of '',i0)') &
stored in the file hello.f90 can then be compiled with the suitable compiler command, and then executed using multiple cores, one for each image. The following table indicates how this works for the various compilers.
g95 coarray console
g95 shared memory
|Compiling||ifort -coarray=distributed -o h.exe hello.f90||ifort -coarray -o h.exe hello.f90||caf -o h.exe hello.f90||g95 -o h.exe hello.f90|
module load mpi.intel
|cocon -n -i4 --batch ./h.exe||./h.exe --g95 images=4|
|Remarks||loading the MPI module assures the correct host file is used for batch jobs||
caf is a compiler wrapper which eventually executes g95. The -n switch for cocon causes standard output from each image to be prepended by the image index.
cocon can also be used in console mode; please read the file $CAF_DOC for details.
- Summary of the coarray feature (as covered in the Fortran 2008 standard) by John Reid. Some coarray features not discussed in this paper have been split off and will be reintroduced via a technical specification.
- Andy Vaught's coarray compendium
- Intel Fortran compiler documentation for versions 12.0 and higher, available from the LRZ web server or from the Intel web site