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export CC=gcc
export FC=gfortran
export CCFLAGS="-g -O2"
export FCFLAGS="-g -O2"

export CC=icc
export FC=ifort
export CFLAGS="-g -O1 -fp-model precise"
export FCFLAGS="-g -O1 -fp-model precise"

We currently recommend not using a higher optimization level than -O1 with the Intel compiler. Failures have been seen with grib_api and the Intel compiler when compiled with -O2.

export CC=cc
export FC=ftn
export CFLAGS="-O1 -G2 -hflex_mp=conservative -hadd_paren -hfp1"
export FCFLAGS="-O1 -G2 -hflex_mp=conservative -hadd_paren -hfp1"

export CC=xlc_r
export FC=xlf90_r
export CFLAGS="-g -O2 -qstrict -qarch=auto -qtune=auto"
export FCFLAGS="-g -O2 -qstrict -qarch=auto -qtune=auto"

For the IBM xlc compiler we recommend disabling the creation of 'shared libraries' which is known to cause problems with some versions of grib_api.

In this example, note the use of the '_r' form of the IBM compiler to ensure grib_api is compiled 'thread-safe'.

export CC=gcc
export FC=gfortran
cmake .... -DCMAKE_C_FLAGS="-g -O2" -DCMAKE_Fortran_FLAGS="-g -O2"

export CC=icc
export FC=ifort
export CFLAGScmake ... -DCMAKE_C_FLAGS="-g -O1 -fp-model precise"
export FCFLAGS -DCMAKE_Fortran_FLAGS="-g -O1 -fp-model precise"