Re: Matrix Multiplication

[Dieter Britz <db@kemi.aau.dk>]

On Wed, 15 Dec 1999, Robert A Duff wrote:

> "Pascal Obry" <pascal_obry@csi.com> writes:
> 
> > Well I don't know what is a fast or slow language !!
> 
> I do.  A fast language is one for which it is feasible to build
> compilers that generate fast code.  A slow language is one for which
> that is not feasible.
> 
> Also I prefer to put the burden of proof on the language advocates --
> that is, a language should be considered "slow" until proven "fast" by
> the existence of at least one good production-quality compiler.
> 
> By this definition, Smalltalk, for example, is slow -- I've never seen a
> Smalltalk compiler that can generate fast code.  Furthermore, it seems
> impossible, without doing all code generation at link time, which I
> claim is not feasible in many cases.
> 
> I don't know whether Fortran is faster than Ada at matrix multiplies,
> but it does seem like a meaningful question to ask.  If you measured
> lots of compilers, you could learn something useful.

This must depend on the specific compiler. These have become better at
optimising code the last couple of decades. Years ago, I often needed
to shift large array sections, and (on a PDP11, under RT11) wrote
myself an assembler-code subroutine to do the shift; that turned out
to run about 100 times as fast as the equivalent Fortran code. I feel
sure that now, there would not be so much difference, if any (but I
don't have an assembler anymore). Later, I compared Pascal and Fortran 77
on a VAX machine, and Fortran was, on average, about twice as fast. It
might depend on what sort of operations you normally program.

-- Dieter Britz alias db@kemi.aau.dk;  http://www.kemi.aau.dk/~db
*** Echelon, bomb, sneakers, GRU: swamp the snoops with trivia! ***