lis_array_qr - Man Page

#include "lis.h"

LIS_INT lis_array_qr(LIS_INT n, LIS_SCALAR a[], LIS_SCALAR q[], LIS_SCALAR r[], LIS_INT *qriter, LIS_SCALAR *qrerr);

Calculate the eigenvalues of matrix A with the QR algorithm.

n

The size of the matrices

a

The array that stores matrix A of size n * n

q

The work array Q of size n * n

r

The work array R of size n * n

a

The array that stores the block upper-triangular matrix with eigenvalues in the block diagonal elements after similarity transformation

qriter

The number of iterations of the QR algorithm

qrerr

The 2-norm of the first subdiagonal element A(2,1) after similarity transformation

The following exit values are returned:

0

The process is normally terminated

unspecified

An error occurred

lis(3)

http://www.ssisc.org/lis/