Re: Matrix Multiplication

Dear Gordon,

It is your article to write. You have picked a hard topic and asked for
comments. You got them.

I do appreciate your comments and your time. Thank you. Unfortunately,
I still did not completely get your points. Hence if you allow I will
ask some more questions.

They pointed out consequences of your choice to
switch to C++ in 1993 and to extol its virtues. Your choice of systems
to compare is certainly idiosyncratic. Python, C++ vrs C and F77 seems
to be more a setup for language wars than about Matrix Programming.
Insisting that comments come with "your code" is following the best
newsgroup language war traditions.

Here I would disagree. The use of several programming languages in one
project is a common practice nowadays, at least what I see. For
example, I am using LAPACK that is written in Fortran 77 and MUMPS
that is written in Fortran 90. ATLAS, TAUCS and UMPFACK are written in
C. My code is in C++ and now I am going to use Python as a scripting
language.

Anyway, do I have a freedom to use a programming language of my choice
or not?

If you want to write about matrix programming then where is the discussion
of MatLab and its clones?

In my text

http://matrixprogramming.com/MatrixMultiply/

there were links to both Matlab and Mathematica.

Fortran 90 lives well in that crowd with its
array operations. Matrix multiply is one of the supplied intrinsics. To
ignore that reality of current practice is to either be misinformed or
out of date.

The matrix multiply is also intrinsic in Matlab, Mathematica and NumPy
and I guess in many other systems. The example with matrix multiply as
intrinsic is at the beginning of my text in NumPy - See mm.py.

In my opinion, everything here depends on whether this intrinsic will
call optimized BLAS or not. If yes, it will be efficient in any
language. If not, then it will be inefficient in any language. Do you
agree with this statement?

Once one has gotten the concepts sorted out with vector and
matrix capabilities then one can go back to the element based operations.
To dismiss F90 with the comment that you only know F77 would appear
to be an admission that you do not want to follow the contemporary style of
use of the array notations.

I see your point here. Thank you. Yes, I should have mentioned the
contemporary style of the array notation that is available in many
modern languages. Will do.

Finally one more question about Fortran 77 and Fortran9*. LAPACK is
written in Fortran 77 and many say that it is the most efficient
library for dense linear algebra (of course, when one uses it with the
optimised BLAS). Well, on Netlib there is Fortran 95 interface to
LAPACK but this is only an interface, the computational engine is
still written in Fortran 77. Could you please make your comment in
this respect?

Thank you again. If you find time to answer questions above, I would
appreciate it.

Best wishes,

Evgenii
.

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