On 2010-01-21 18:27, Mark Moll wrote:
On Jan 21, 2010, at 10:22 AM, Jed Brown wrote:
On Thu, 21 Jan 2010 09:17:22 -0600, Mark Moll <mm...@cs.rice.edu> wrote:
You *can* use the Fortran BLAS/LAPACK libraries with C/C++ code.
Yes, this is actually very common, but check_fortran_function_exists
works by trying to link an actual Fortran program. When calling from C,
you have to know how Fortran names are mangled which means testing a
number of common choices. Nobody put this logic into these Find
modules, but it would be nice because many (most?) users of BLAS/Lapack
need to call it from both Fortran and C so they need to know how the
symbols are mangled. CBLAS/CLapack are entirely different beasts, but I
know of far more C projects that call the Fortran versions directly than
use the C bindings.
Wouldn’t it be possible to use “nm” to detect the Fortran name mangling? For
example:
On OS X, default LAPACK library:
nm /usr/lib/liblapack.dylib | grep cheev$ | awk '{print $3}’
_cheev
On Linux, using MKL:
nm /opt/intel/Compiler/11.1/056/mkl/lib/em64t/libmkl_intel_lp64.a | grep cheev$
| awk '{print $3}'
cheev
(Of course the “grep” and “awk” commands can be replaced with some cmake string
commands, if you want to make it a bit more portable.)
This would indeed not work on systems that do not provide an nm-like
utility, but there is an system-independent way to do this:
Use a set of small C programs that will call a LAPACK routine with any
of the naming conventions:
int main() {
_cheev( ... );
}
void stdcall__ CHEEV( ... );
int main() {
CHEEV( ... );
}
etc.
Whichever of the programs can be successively linked (no unresolved
symbols) is the indication of the used name mangling scheme.
Caveats:
- Some Fortran compilers add two underscores when the name of the
routine contains at least one underscore. So that variation must
be tested too.
- String arguments pose an extra complication - the string length is
usually added as a separate argument, but it may come at the end
OR right after the string argument. This is not detectable by
the above method.
Regards,
Arjen
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