Subject: Lanczos Algorithm request

From: Stefan Tsonchev <[email-masked]>
Date: Wed, 29 Jul 1998 13:06:22 -0400 (EDT)

Hello:

I need a program to solve the eigenvalue problem for a very large (tens
of thousands of lines) sparse matrix. It should use the Lanczos methos
for finding the lowest eigenvalues (which is what I need). All the
programs that I have seen seem to require the matrix as an input.
However, the advantage of the problem that I am dealing with is that I
do not need to generate the matrix. I have a simple rule for generating
its elements, only a small number of which are non-zero.

I wonder if someone could refer me to a program that does solve this
kind of problem without generating the matrix, but only needs to be
given the rule for creating its elements? I will appreciate your help.

Stefan Tsonchev, 
[email-masked]

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From: Matt Challacombe T-12 <[email-masked]>
Date: Wed, 29 Jul 1998 11:31:01 -0600 (MDT)

Hi Stefan,

Try ARPACK, available from netlib.

Cheers, Matt

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Matt Challacombe
Los Alamos National Laboratory    http://www.t12.lanl.gov/~mchalla/
Theoretical Division              email: [email-masked]
Group T-12, Mail Stop B268        phone:   (505) 665-5905
Los Alamos, New Mexico  87545     fax:     (505) 665-3909
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On Wed, 29 Jul 1998, Stefan Tsonchev wrote:

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