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Re: [wwwdocs] Add "-fexternal-blas" to gcc-4.3/changes.html


Hi,

Richard Guenther wrote:
> Does it work with BLAS only or with any lapack style library?  In this
> case at least the documentation should read like "calls to a linear
> algebra library
> like BLAS or LAPACK for matrix".  Of course in that case I also
> dislike the option name, but
> I don't have a particular better idea either.

It works with any library, which provides sgemm, dgemm, cgemm and zgemm
and supports the same arguments as Netlib.org's BLAS. It thus works with
Atlas, AMD Core Math Library, NAG Fortran Library, Intel Mathe Kernel
Library, gotoBLAS, Sun Performance Libraray etc. In fact, the idea is
that an optimized library is used.

For me BLAS and a library, which provides the routines of BLAS, are in
this context the same. And thus I also like the option name
"-fexternal-blas" (which was not coined by me, by the way).

For me at least "a linear algebra library like BLAS or LAPACK" is much
harder to gasp. Is now LAPACK or BLAS needed? Answer: only BLAS. A
"linear algebra library like" also is rather vague; what routines are
needed?

But if you think that many people think of only Netlib's BLAS when one
uses the term "BLAS", we indeed need to find a better wording. (Here and
maybe [or maybe not] also in the manual, were we currently use:
http://gcc.gnu.org/viewcvs/trunk/gcc/fortran/invoke.texi?r1=117948&r2=117947&pathrev=117948
"This option will make gfortran generate calls to BLAS functions for
some matrix operations like @code{MATMUL}, instead of using our own
algorithms, if the size of the matrices involved is larger than a given
limit (see @command{-fblas-matmul-limit}). This may be profitable if an
optimized vendor BLAS library is available. The BLAS library will have
to be specified at link time.")

Tobias


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