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Re: Eigen value problem
- To: <vjohn111 at hotmail dot com>, <gsl-discuss at sources dot redhat dot com>
- Subject: Re: Eigen value problem
- From: "Jim Love" <Jim dot Love at asml dot com>
- Date: Mon, 01 Oct 2001 12:30:06 -0400
This program works for me just fine (gsl 0.9.2 on win32 and redhat 7.1). Here is the output for a 2x2 and a 3x3:
The Input Matrix:
1 2
2 1
The EigenValues :
eigenvalue = 3
eigenvalue = -1
The Input Matrix:
4 1 1
1 2 2
1 2 9
The EigenValues :
eigenvalue = 9.79216
eigenvalue = 3.93673
eigenvalue = 1.27111
James A. Love
X4477
Pager 1-800-286-1188 Pin# 400659
>>> "Varghese John" <vjohn111@hotmail.com> 10/01/01 11:51AM >>>
Hi,
I am having problems with the following program.
trying to get eigen values for the 2x2 matrix, and the program hangs?
--it works fine for a 3x3 matrix!
thanks.
vj
-----------------------------------------------
#include <gsl/gsl_eigen.h>
#include <stdio.h>
#include <math.h>
#define TestSize 2
void GetEigen1();
void GetEigenvaluesForSymmMat( gsl_matrix * m, int mSize, gsl_vector * v);
int main(){
GetEigen1();
return(0);
}
void GetEigen1(){
int i;
int j;
int x;
gsl_matrix * m = gsl_matrix_alloc(TestSize, TestSize);
gsl_matrix_set_zero(m);
/* matrix = ((1, 2), (2, 1)) */
gsl_matrix_set(m, 0, 0, 1.0);
gsl_matrix_set(m, 0, 1, 2.0);
gsl_matrix_set(m, 1, 0, 2.0);
gsl_matrix_set(m, 1, 1, 1.0);
/* matrix = ((4, 1, 1), (1, 2, 2), (1, 2, 9)) */
/*
gsl_matrix_set(m, 0, 0, 4.0);
gsl_matrix_set(m, 0, 1, 1.0);
gsl_matrix_set(m, 0, 2, 1.0);
gsl_matrix_set(m, 1, 0, 1.0);
gsl_matrix_set(m, 1, 1, 2.0);
gsl_matrix_set(m, 1, 2, 2.0);
gsl_matrix_set(m, 2, 0, 1.0);
gsl_matrix_set(m, 2, 1, 2.0);
gsl_matrix_set(m, 2, 2, 9.0);
*/
printf("The Input Matrix: \n");
for (i = 0; i < TestSize; i++){
for (j = 0; j <TestSize; j++){
printf("%6.4g \t", gsl_matrix_get (m, i, j));
}
printf("\n");
}
printf("\n");
//use this vector to store the eigen values.
gsl_vector *v=gsl_vector_alloc(TestSize);
GetEigenvaluesForSymmMat( m, TestSize, v);
printf("The EigenValues : \n");
//print the result
for (x = 0; x < TestSize; x++)
{
printf("eigenvalue = %g\n", gsl_vector_get(v, x));
}
}
//This function computes the eigen values of a symmetric block
//and returns the ordered eigen values in the vector v.
void GetEigenvaluesForSymmMat( gsl_matrix * m, int mSize, gsl_vector * v) {
gsl_vector *eval = gsl_vector_alloc (mSize);
gsl_vector_set_zero(eval);
gsl_matrix *evec = gsl_matrix_alloc (mSize, mSize);
gsl_matrix_set_zero(evec);
gsl_eigen_symmv_workspace * w =
gsl_eigen_symmv_alloc (mSize);
gsl_eigen_symmv (m, eval, evec, w);
gsl_eigen_symmv_free(w);
gsl_eigen_symmv_sort (eval, evec, GSL_EIGEN_SORT_ABS_DESC);
gsl_vector_memcpy(v, eval);
}
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