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On 14/12/07 14:12, Matthias Langer wrote:
> F77="ifort" FC="ifort" FFLAGS="-O3 -xO" emerge -av openmpi
This how it should be. To make it automatically reproducible, specify
environment variables in the configuration files.
> Maybe someone can explain to me what positive side effects the removal
> of the ifc USE flag has - and why this flag is generally discouraged.
Positive side effect: avoid cluttering the tree. Why icc/ifc are
discouraged: you can always try to compile every C/C++ package with
CC=icc and fortran packages with F77=ifort or FC=ifort. Packages which
do specify more options with e.g. --enable-icc and friends can be easily
worked out with the toolchain-funcs and fortran eclass, and most of the
time they do nothing more than specify the environment variables.
If we allow icc/ifc flags, at some point, we could allow a whole bunch
of other compiler flags such as "sunstudio". New keywords for compilers
could be a better idea, but I doubt we have the human resources to test
them.
> The reason it disappeared is that it makes gfortran horribly slow when
> compiling against mpi. This is not the case with ifc, and therefore the
> old ebuild in bugzilla emitted a bold warning when emerging with
> USE="-ifc f90-typesafe" but kept quiet if USE="ifc f90-typesave". Thus
> it *did make sense* to control it with a USE flag, at least with the
> "ifc" USE flag being around also.
If the f90-typesafe options always improve compilation time with
gfortran only, why not using something like this (modified from the
openmpi bump bug):
if use fortran; then
case ${FORTRANC} in
g77) myconf="${myconf} --disable-mpi-f90" ;;
gfortran) myconf="${myconf} --with-mpi-f90-size=medium"
myconf="${myconf} --with-f90-max-array-dim=4" ;;
if*) myconf="${myconf} blah" ;;
*) die "unsupported fortran compiler: ${FORTRANC}"
esac
else
myconf="${myconf} --disable-mpi-f90 --disable-mpi-f77"
fi
Let the ebuild make reasonable choices instead of making a user trying
to find out about undocumented use flags.
- --
Sébastien
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