(Release 6.3)

Prerequisites:
    * GNU Make
    * gfortran 4.3 or higher
    * (possibly) other Fortran 90 compilers
    * fftw3
      install in ubuntu: apt-get install libfftw3-dev
	
Prerequisites for building the parallel version:
    * MPI (Message Passing Interface) libraries and
      implementation/environment:
      MPICH2    [http://www.mcs.anl.gov/research/projects/mpich2/] 
      -or-
      OPENMPI   [http://www.open-mpi.org/]
    * also see README_PARALLEL in tests/*/

To build the ORAC(6.x) executable program:

    cd $HOME                                          # go to your home root dir   
    tar zxvf DOWNLOADS_LOCATION/orac.6_3.tar.gz       # untar the orac tar file
    cd orac.6_3/src                                   # go to the src dir
    ./configure [options]                             # generate the Makefile
    make                                              # generate the executable

    This will create an executable orac in the target directory as
    specified in [options].  For example, to generate a target for
    Intel/ifort with OpenMP and MPI support and fftw libraries type:    

    ./configure -Intel -FFTW -OMP -MPI 
    make 

    A target "orac" is created in the directory /INTEL-FFTW-OMP-MPI.
    
    To list all configure options, type: 
    ./configure -help.  

    If you want to use the fftw libraries, you must have these
    installed in your system. For parallel execution, libfftw3,
    libfftw3_omp, libfftw3_threads are needed. In Debian/Ubuntu
    systems these libraries are provided in the packages fftw3 and
    fftw3-dev.  

    An alternative path for fftw libraries can be specified in the
    -FFTW configure option [-FFTW[=alt_path]].
    
    The file src/config.H sets the dimensions for the program. The
    current settings work for the attached tests; the user may have to
    change this setting for running her/his project.
    
    The program has been tested on Linux platforms. On other
    platforms, the configure and Makefile.in files may need some
    hacking.  The package is known to compile and run with gcc > 4.8 and
    Intel Fortran Compiler (10.1 to 21.7) both in 32- and 64- bit
    architecture; XL Fortran for AIX (V12.1-V14.1) and XL C/C++ for
    AIX (V10.1-V12.0); PGI Fortran 2003-2022.
