Article View: sci.math.num-analysis
Article #387Bug in Numerical Recipes? (ludcmp)
From: Behnam TABATABAI
Date: Mon, 31 Aug 1992 12:51
Date: Mon, 31 Aug 1992 12:51
37 lines
1464 bytes
1464 bytes
Hi!
It seems that the function `ludcmp' for LU-decomposition does not work
well. After decomposition of a matrix in the form
( 0 0 2 )
| 0 3 0 |
( 1 0 0 )
the content of the indx-vector is (3,2,3) instead of (3,2,1). The following
is the code for this example:
#include <stdio.h>
main()
{
float **a, d;
int n, *indx;
extern float **matrix();
extern int *ivector();
extern void ludcmp();
a = matrix( 1, 3, 1, 3 );
indx = ivector( 1, 3 );
a[1][1] = 0.0; a[1][2] = 0.0; a[1][3] = 2.0;
a[2][1] = 0.0; a[2][2] = 3.0; a[2][3] = 0.0;
a[3][1] = 1.0; a[3][2] = 0.0; a[3][3] = 0.0;
ludcmp( a, 3, indx, &d );
for ( n = 1; n <= 3; n++ ) printf( "indx[%d] = %d\n", n, indx[n] );
}
Do I make a mistake? Does anybody has an idea?
Thanks in advance!
Behnam
--
Behnam Tabatabai, | e-mail: tab@piis10.joanneum.ac.at
Joanneum Research, Graz, Austria | tabatabai@joanneum.ada.at
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Newsgroups: sci.math.num-analysis Path: arc1-ca.pugleaf.net!sparky!uunet!news.univie.ac.at!news.tu-graz.ac.at!piis10.joanneum.ac.at!tab From: tab@piis10.joanneum.ac.at (Behnam TABATABAI) Subject: Bug in Numerical Recipes? (ludcmp) Message-ID: <1992Aug31.125142.8521@news.tu-graz.ac.at> Sender: news@news.tu-graz.ac.at (USENET News System) Nntp-Posting-Host: piis10.joanneum.ac.at Organization: Joanneum Research, Graz, Austria X-Newsreader: Tin 1.1 PL5 Date: Mon, 31 Aug 92 12:51:42 GMT Lines: 37