On 7. Jul, 2009, at 11:08, Marcel Loose wrote:
[fixed quoting]
On Tue, 2009-07-07 at 10:32 +0200, Michael Wild wrote:
On 7. Jul, 2009, at 10:11, Marcel Loose wrote:
Hi all,
I noticed that FindLAPACK and FindBLAS require that you enable
Fortran
as language, which causes CMake to check for a working Fortran
compiler.
IMHO, you only need the fortran runtime libraries, cause you're only
linking against the Lapack/Blas libraries. Most Linux distro's have
separate packages for compiler and runtime libraries.
Is there a good reason for FindLAPACK and FindBLAS to require a
working
Fortran compiler?
Best regards,
Marcel Loose.
That's probably because these modules ONLY search for the Fortran
interfaces. Usually one needs a different set of libraries for cblas
and clapack. Also the function names to check for are different (e.g.
cblas_dgemm versus dgemm).
Perhaps someone finds the time to write FindCBLAS.cmake and
FindCLAPACK.cmake... But honestly, if you look at FindBLAS.cmake,
that
is quite tough as the various vendor implementations differ strongly
in library names, required compiler flags etc. Linking against Intel
MKL is just a night-mare!
I hope this explains it a bit (although the answer is probably not
very satisfying).
Michael
Hi Michael,
I'm not surprised that it's quite difficult to make checks for
Lapack/Blas work cross-platform and cross-vendor.
But the essence of my question was: why do I need a Fortran compiler!?
As you wrote in your answer: That's probably because these modules
ONLY
search for the Fortran interfaces. Now, that's exactly what they
should
do: search for interfaces! Interfaces: that's libraries in the case of
Fortran. No compiler is required IMHO, cause I'm only linking against
(Fortran) libraries.
Best regards,
Marcel Loose.
Problem is, it is going to be difficult to check a Fortran interface
with a C-compiler. Sometimes the names are all upper case, sometimes
all lower case, sometimes there's a trailing underscore at the end of
all symbols, sometimes even two if the name already contains an
underscore. All of this makes writing a check_function_exists macro
quite involved.
An yes, a compiler IS required. How else do you propose to check an
interface? You could use "nm" on UNIX platforms and "DUMPBIN.exe" on
Windows, but then you're not sure that the code is going to link
successfully because there might be an incompatibility of name-
mangling schemes between compiler, linker and library.
This is exactly one of the reasons why there is CBLAS and CLAPACK.
Firstly they have interfaces suitable to C-languages, do not require
the user to provide work-arrays, and all name-mangling issues have
already been dealt with.
Cheers
Michael
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