Newsgroups: comp.lang.apl
Path: watmath!watserv2.uwaterloo.ca!torn!spool.mu.edu!agate!ames!haven.umd.edu!uunet!psinntp!juliet!news
From: jja@fnbc.com (Joseph Alotta)
Subject: Re: Matrix Inverse in APL2
Message-ID: <1993Jan13.150939.7200@fnbc.com>
Keywords: matrix
Sender: news@fnbc.com
Organization: First National Bank Of Chicago, Chicago IL, USA
References: <1474@kepler1.rentec.com>
Date: Wed, 13 Jan 93 15:09:39 GMT
Lines: 36

> >I realize that for a matrix so large, it would probably take a LONG
> >time to run.  But could anyone guestimate what kind of time I'm
> >looking at?  Minutes?  Hours?  If it means anything, most of the
> >entries in the matrix will be zero.
> 
> You should probably take advantage of the large number of zeros, (in the
> jargon you may have a 'sparse' matrix). The best thing there is to
> skip using APL at all and find a routine which may be suited to your
> particular matrix which can perhaps be used from within APL2. In order
> to get more out of the Internet, you should probably post a non-APL
> specific query with a reasonable description of your matrix problem to
> sci.math.num-analysis. Two books you should get some handle on, although
> you may need some elementary numerical analysis books before you can
> get very far, are Golub and van Loan's _Matrix Computations_ and Hanson
> and Lawson's _Solving Least Squares Problems_, although Golub and van
> Loan mostly supercedes Hanson and Lawson.
> 
get a copy of Numerical Recipes In C, second edition, Cambridge
Press.  you'd want to have a copy anyhow for reference.  there is
a whole section on matrix inversions including a few routines
for sparse matrices.  i have used NRiC and found the routinues to
be quite good.

otherwise post on sci.math.num-analysis and maybe someone would
mail you a routine.

joe.

--
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! joe alotta                                    jja@fnbc.com !                                               
!                                             (312) 732-3439 !
!                                                            !
! "The main thing is to keep the main thing the main thing." !
! Dr. George Sweeney                                         !
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