claesy (l)  Linux Man Pages
claesy: computes the eigendecomposition of a 2by2 symmetric matrix ( ( A, B );( B, C ) ) provided the norm of the matrix of eigenvectors is larger than some threshold value
NAME
CLAESY  computes the eigendecomposition of a 2by2 symmetric matrix ( ( A, B );( B, C ) ) provided the norm of the matrix of eigenvectors is larger than some threshold valueSYNOPSIS
 SUBROUTINE CLAESY(
 A, B, C, RT1, RT2, EVSCAL, CS1, SN1 )
 COMPLEX A, B, C, CS1, EVSCAL, RT1, RT2, SN1
PURPOSE
CLAESY computes the eigendecomposition of a 2by2 symmetric matrix(
ARGUMENTS
 A (input) COMPLEX
 The ( 1, 1 ) element of input matrix.
 B (input) COMPLEX
 The ( 1, 2 ) element of input matrix. The ( 2, 1 ) element is also given by B, since the 2by2 matrix is symmetric.
 C (input) COMPLEX
 The ( 2, 2 ) element of input matrix.
 RT1 (output) COMPLEX
 The eigenvalue of larger modulus.
 RT2 (output) COMPLEX
 The eigenvalue of smaller modulus.
 EVSCAL (output) COMPLEX
 The complex value by which the eigenvector matrix was scaled to make it orthonormal. If EVSCAL is zero, the eigenvectors were not computed. This means one of two things: the 2by2 matrix could not be diagonalized, or the norm of the matrix of eigenvectors before scaling was larger than the threshold value THRESH (set below).
 CS1 (output) COMPLEX

SN1 (output) COMPLEX
If EVSCAL .NE. 0, ( CS1, SN1 ) is the unit right eigenvector
for RT1.