Difference between revisions of "Programming/Fortran"
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− | '''Note''' : mpifort would be used as the compiler wrapper if the above example used [[Applications/OpenMPI|openMPI]]. | + | * '''Good practice''' when compiling is to only use compiler optimization flags at the final stages towards production release, Intel's fortran compiler usually has -O2 set by default, so placing compiler flag -O0 would be necessary to turn this off. |
+ | * '''Note''' : mpifort would be used as the compiler wrapper if the above example used [[Applications/OpenMPI|openMPI]]. | ||
== Usage Examples == | == Usage Examples == |
Revision as of 08:50, 16 April 2018
Contents
Programming Details
Fortran (formerly FORTRAN, derived from Formula Translation) is a general-purpose, imperative programming language that is especially suited to numeric computation and scientific computing. The GFortran compiler is fully compliant with the Fortran 95 Standard and includes legacy F77 support. In addition, a significant number of Fortran 2003 and Fortran 2008 features are implemented. Intel's Fortran compiler (ifort) is also compliant with Fortran back to F77 and earlier to most implementations.
There is direct support for openMP and openMPI. |
Programming example
Non Parallel Example
program variableTesting implicit none ! declaring variables integer :: total,average complex :: cx logical :: done character(len=80) :: message ! a string of 80 characters !assigning values total = 20000 average = 1666 done = .true. message = "A big Hello from HPC" cx = (3.0, 5.0) ! cx = 3.0 + 5.0i if (total .ge. average) then print *, total, " greater or equal than average" else print *, total, " less than average" endif Print *, average Print *, cx Print *, done Print *, message end program variableTesting
Parallel Example (openMP)
program helloworld use omp_lib implicit none !$OMP PARALLEL !$OMP CRITICAL print *,'Hello from thread number',OMP_GET_THREAD_NUM() !$OMP END CRITICAL !$OMP END PARALLEL end program helloworld
Modules Available
The following modules are available:
- module add gcc/4.9.3 (GNU compiler)
- module add intel/compiler/64/2016.2.181 (Intel compiler)
Note : It is generally accepted that the intel compiler generates faster code on Intel hardware than gcc, although gcc is generally more compatible with a wide range of hardware.
Compilation
The program would be compiled in the following way, optional Intel compiler available too:
[username@login01 ~]$ module add gcc/4.9.3 [username@login01 ~]$ gfortran -o testFortran testFortran.f03
- Good practice when compiling is to only use compiler optimization flags at the final stages towards production release, Intel's fortran compiler usually has -O2 set by default, so placing compiler flag -O0 would be necessary to turn this off.
- Note : mpifort would be used as the compiler wrapper if the above example used openMPI.
Usage Examples
Batch example
#!/bin/bash #SBATCH -J openmpi-single-node #SBATCH -N 1 #SBATCH --ntasks-per-node 28 #SBATCH -o %N.%j.%a.out #SBATCH -e %N.%j.%a.err #SBATCH -p compute #SBATCH --exclusive echo $SLURM_JOB_NODELIST module purge module add gcc/4.9.3 export I_MPI_DEBUG=5 export I_MPI_FABRICS=shm:tmi export I_MPI_FALLBACK=no /home/user/CODE_SAMPLES/OPENMP/demo
[username@login01 ~]$ sbatch demo.job Submitted batch job 239552
HDF5 Library
HDF5 is a versatile data model that can represent very complex data objects and a wide variety of metadata, which is ideal for data which has a large disparity to be stored in a standard format description. NetCDF is a similar system as well.
(Example from the HDF group)
PROGRAM H5_CRTDAT USE HDF5 ! This module contains all necessary modules IMPLICIT NONE CHARACTER(LEN=8), PARAMETER :: filename = "dsetf.h5" ! File name CHARACTER(LEN=4), PARAMETER :: dsetname = "dset" ! Dataset name INTEGER(HID_T) :: file_id ! File identifier INTEGER(HID_T) :: dset_id ! Dataset identifier INTEGER(HID_T) :: dspace_id ! Dataspace identifier INTEGER(HSIZE_T), DIMENSION(2) :: dims = (/4,6/) ! Dataset dimensions INTEGER :: rank = 2 ! Dataset rank INTEGER :: error ! Error flag ! ! Initialize FORTRAN interface. ! CALL h5open_f(error) ! ! Create a new file using default properties. ! CALL h5fcreate_f(filename, H5F_ACC_TRUNC_F, file_id, error) ! ! Create the dataspace. ! CALL h5screate_simple_f(rank, dims, dspace_id, error) ! ! Create the dataset with default properties. ! CALL h5dcreate_f(file_id, dsetname, H5T_NATIVE_INTEGER, dspace_id, & dset_id, error) ! ! End access to the dataset and release resources used by it. ! CALL h5dclose_f(dset_id, error) ! ! Terminate access to the data space. ! CALL h5sclose_f(dspace_id, error) ! ! Close the file. ! CALL h5fclose_f(file_id, error) ! ! Close FORTRAN interface. ! CALL h5close_f(error) END PROGRAM H5_CRTDAT
Further Information
- http://www.tutorialspoint.com/fortran/
- https://en.wikipedia.org/wiki/OpenMP
- http://www.openmp.org/
- https://computing.llnl.gov/tutorials/openMP/
- https://en.wikipedia.org/wiki/Open_MPI
- https://www.open-mpi.org/
- https://www.hdfgroup.org/