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

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SYNOPSIS

DESCRIPTION

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SEE ALSO