Newsgroups: comp.lang.apl
Path: watmath!watserv1!utgpu!cs.utexas.edu!wupost!darwin.sura.net!haven.umd.edu!socrates!socrates!rockwell
From: rockwell@socrates.umd.edu (Raul Deluth Miller-Rockwell)
Subject: Re: APL execution efficiency revisited
In-Reply-To: andrew@rentec.com's message of 24 Mar 92 15:34:27 GMT
Message-ID: <ROCKWELL.92Mar25000046@socrates.umd.edu>
Sender: rockwell@socrates.umd.edu (Raul Deluth Miller-Rockwell)
Organization: Traveller
References: <920322073241_70530.1226_CHC87-1@CompuServe.COM>
	<1992Mar23.185558.2647@csi.jpl.nasa.gov>
	<ROCKWELL.92Mar23224842@socrates.umd.edu> <756@kepler1.rentec.com>
Date: Wed, 25 Mar 1992 05:00:46 GMT
Lines: 28

I wrote:
   >Andrew Mullhaupt:
   >   |> No vendor has yet (so far as I know) optimized
   >   |>     first plus.times / (vector of matrices)

Andrew Mullhaupt:
   CHECK YOUR ATTRIBUTIONS, PLEASE! I did not say this. 

Sorry about that.  Articles here expire after three days, and I made
the mistake of trusting a second or third hand attribution.

   Optimizing the calculation of a matrix product is a classical
   problem in computer science. The idea is that some of the
   intermediate products are much smaller than others, depending on
   the sequence of shapes.  In order to 'efficiently' compute the
   product, you usually have to solve a dynamic program whose inputs
   are these shapes, and then do the matrix arithmetic.

Ah... I think I see the problem.  I was thinking of plus.times being
used to reduce a rank three matrix, not a nested setup where each of
the matrices are differently dimensioned.  You were thinking of the
latter case.

Um.. before I get into the mechanisms one might use for implementing
this, what sort of applications does this have?

-- 
Raul Deluth Miller-Rockwell                   <rockwell@socrates.umd.edu>
