[Numpy-discussion] numpy build: automatic fortran detection
Fri Jun 17 16:00:09 CDT 2011
On Mon, Jun 13, 2011 at 8:53 PM, Russell E. Owen <email@example.com> wrote:
> In article <BANLkTikODians0UJrdKPUdfFO8agPnXk7g@mail.gmail.com>,
> Ralf Gommers <firstname.lastname@example.org> wrote:
> > On Thu, Jun 9, 2011 at 11:46 PM, Russell E. Owen <email@example.com> wrote:
> > > What would it take to automatically detect which flavor of fortran to
> > > use to build numpy on linux?
> > >
> > You want to figure out which compiler was used to build BLAS/LAPACK/ATLAS
> > and check that the numpy build uses the same, right? Assuming you only
> > about g77/gfortran, you can try this (from
> > http://docs.scipy.org/doc/numpy/user/install.html):
> > """
> > How to check the ABI of blas/lapack/atlas
> > -----------------------------------------
> > One relatively simple and reliable way to check for the compiler used to
> > build a library is to use ldd on the library. If libg2c.so is a
> > this means that g77 has been used. If libgfortran.so is a a dependency,
> > gfortran has been used. If both are dependencies, this means both have
> > used, which is almost always a very bad idea.
> > """
> > You could do something similar for other compilers if needed. It would
> > to know exactly what problem you are trying to solve.
> I'm trying to automate the process of figuring out which fortran to use
> because we have a build system that should install numpy for users,
> without user interaction.
I assume you're installing scipy as well? There's no Fortran code in numpy.
> We found this out the hard way by not specifying a compiler and ending
> up with a numpy that was mis-built (according to its helpful unit tests).
> However, it appears that g77 is very old so I'm now wondering if it
> would make sense to switch to gfortran for the default?
This makes sense. Only if you're building on Windows and build with MinGW
you have to give it some more thought - we're still building the distributed
binaries with g77.
> I think our own procedure will be to assume gfortran and complain to
> users if it's not right. (We can afford the time to run the test).
> > > The unit tests are clever enough to detect a mis-build (though
> > > surprisingly that is not done as part of the build process), so surely
> > > it can be done.
> > >
> > The test suite takes some time to run. It would be very annoying if it
> > by default on every rebuild. It's easy to write a build script that
> > numpy, then runs the tests, if that's what you need.
> In this case the only relevant test is the test for the correct fortran
> compiler. That is the only test I was proposing be performed.
> There's not a single test like that in the test suite, unless I missed
something. But you can easily implement it for gfortran/g77.
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