lis_array_qr(3f)

NAME
lis_array_qr - calculate the eigenvalues with the QR algorithm

SYNOPSIS
subroutine lis_array_cgs(LIS_INTEGER n, LIS_SCALAR a(), LIS_SCALAR q(), LIS_SCALAR r(), LIS_INTEGER qriter, LIS_SCALAR qrerr, LIS_INTEGER ierr);

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

SEE ALSO
lis(3)

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