Band matrix storage issue

galuha — Tue, 14 Dec 2004 10:43:27 GMT

I get wrong result while computing eigenvalues of a symmetric matrix in band storage using LAPACK routine "dsbev".
Here is code example. Consider matrix A=E. A is in band storage AB with one additional zero super-diagonal.

#include "include/mkl.h"
#define N 4

int main() {

double AB[2]={0,0,0,0,1,1,1,1};
int n=N;
int ldab=2;
int kd=1;
int lwork=3*N;
int ldz=1;
int info;
double work[3*N];
double w;
double z[1];
dsbev ("N", "U", &n, &kd, *AB, &ldab, w, z, &ldz, work, &info);

printf( "Eigenvalues: %g %g %g %g ", w[0], w[1], w[2], w[3]);

return 0;
}

The solution of MKL is:
-0.801938 0 0.554958 2.24698
But as we all know correct result is 1 1 1 1
What's wrong here?

Thank you.

Message Edited by galuha@gmail.com on 12-13-2004 06:50 PM

Update

galuha — Tue, 14 Dec 2004 18:01:08 GMT

Sorry for stupid question, just woke up with fresh head and fixed it

Re: Update

Intel_C_Intel — Thu, 16 Dec 2004 03:30:55 GMT

Glad we could help :-) --Bruce

topic Re: Update in Intel® oneAPI Math Kernel Library

Band matrix storage issue

Update

Re: Update