Intel ifort 18 compiler replaces -openmp with -qopenmp

[davegill]

Here is a simple Fortran program that exhibits different behavior when the OpenMP compile-time option is activated:

       program mat_mult
#ifdef _OPENMP
       print *,'yep, this is OpenMP parallel'
#else
       print *,'nope, this is NOT OpenMP parallel'
#endif       
       end program

Here is an older Intel ifort compiler:

> ml | grep intel

Currently Loaded Modules:
  1) ncarenv/1.2     3) numpy/1.13.3           5) scipy/0.19.1       7) intel/17.0.1          9) mpt/2.15f
  2) python/2.7.13   4) netcdf4-python/1.2.7   6) matplotlib/2.0.2   8) ncarcompilers/0.4.1  10) netcdf/4.6.1

> ifort -openmp -o mat_mult mat_mult.F

We get a warning message about deprecated options:

ifort: command line remark #10411: option '-openmp' is deprecated and will be removed in a future release. Please use the replacement option '-qopenmp'

However, the executable is built and can run.

> mat_mult
 yep, this is OpenMP parallel

When switching to the newer Intel ifort compiler, the -openmp option has now been removed.

> ml intel/18.0.1
> ifort -openmp -o mat_mult mat_mult.F

Which gives us this output

ifort: command line error: option '-openmp' is not supported. Please use the replacement option '-qopenmp'

As expected, the new -qopenmp option is OK

> ifort -qopenmp -o mat_mult mat_mult.F
> mat_mult
 yep, this is OpenMP parallel

I tested this on WRF. The -qopenmp option seems safe at least going back to ifort 16.0.1:

1. New compiler (tested on WRF and test program)

• The intel/18.0.1 builds with OpenMP when the -qopenmp option replaces the deprecated -openmp.
• The intel/18.0.1 does not build with OpenMP with the -openmp option.

2. Older compiler (tested on WRF and test program)

• The intel/17.0.1 builds with OpenMP when the -qopenmp option replaces the deprecated -openmp.
• The intel/17.0.1 builds with OpenMP with the -openmp option.

3. Even older compiler (tested only on test program)

• The intel/16.0.1 builds with OpenMP when the -qopenmp option replaces the deprecated -openmp.
• The intel/16.0.1 builds with OpenMP with the -openmp option.

[davegill]

@mgduda @kkeene44
Michael and Kelly,
I found this -openmp issue with intel 18 and greater doing regression testing both on my Mac and on cheyenne. We should make sure that if WPS, MPAS, or any WRF post-procs use OpenMP, the new -qopenmp option is substituted.