[Matrix-SIG] Multipack

[Andrew P. Mullhaupt]

> With the availability of g77 on many platforms (including Windows) is it
> that much of a problem to require a Fortran compiler to compile?

It can be. The performance of most Fortran packages is extremely dependent
on compiler switches. The only justification for using original Fortran is
performance. Our experience with the Sun Performance Library is that orders
of magnitude of performance can be lost by failure to use exactly the right
switches, and one has to use ones which are not necessarily compatible with
all the other switches. We've resorted to rewriting some of the Sun
Performance Library BLAS to get optimal performance, and as it happens we
were unable to get the best performance with Fortran code, so we have a
sandwich of C code calling Fortran calling our C code. We gained a factor of
between 3 and 5 on the QR decomposition of large matrices, so it was worth
it.

Later,
Andrew Mullhaupt