lis_array_qr(3)

NAME
lis_array_qr - calculate the eigenvalues with the QR algorithm

SYNOPSIS
#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);

DESCRIPTION
Calculate the eigenvalues of matrix A with the QR algorithm.

INPUT

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

OUTPUT

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

EXIT STATUS
The following exit values are returned:

0   The process is normally terminated

unspecified
    An error occurred

SEE ALSO
lis(3)

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