Re: Matrix Multiplication

Hello Gordon,

Thank you for your comments.

If one were looking at this like a referee one would be questioning an
author who seems to like to use a 30 year old version of Fortran.
There are three revisions since 1977. Fortran 90 introduced a lot
of matrix operations which are never mentioned.

I have written that I know Fortran 77 only and I have mentioned that
the newer versions are available. If you are interested why, the
answer is simple - I have switched to C++ long ago.

You can find my comments Fortran vs. C++ here

http://evgenii.rudnyi.ru/doc/misc/fortran.txt

but we do have to agree on this. Taste differs.

When an author goes out of the way to "think old" one wonders how much
of the rest of the material has the same attributes.

I would appreciate if you will be more specific here.

Both a good implementation of an interpreter and of Fortran 90 are free
to use the best available subroutine libraries for their purposes. The
GNU successor to G77 may or may not have reached the maturity of using
a highly optimized run time for matrix multiply.

Is Intel Fortran good? If you want it to, I will compile the code with
it the next week.

By the way, g95 produces exactly the same results as g77 with this
code. If you could donate the code in newer Fortran, please. It would
be my pleasure to compile it and compare timing.

There is also the question of the intended audience for an introductory
text and whether that audience should be treated to content which is so
dated.

I am not sure I understand you. Do you mean that NumPy, C, C++ and
ATLAS are outdated?

In a fast skim I noticed some comments on memory issues. I did not
notice comments on the issues of size scaling when the matrix fits in the
cache memory and when it does not. When it does not then is the issue of
subscript order that may or may not be cache friendly. The advice that
good subroutine packages deal with such issues is good. One would like
some indication of the problem they address even if the full technical
nature of the solution is not given. Keeping such a discussion both
accurrate and introductory is not easy.

Well, the goal was learning by doing. One first observe something and
then starts thinking why it is. I guess that it is understandable that
a matrix of 1000x1000 does not fit in the processor cache.

Best wishes,

Evgenii
http://MatrixProgramming.com
.

Relevant Pages

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