GSP
Quick Navigator

Search Site

Unix VPS
A - Starter
B - Basic
C - Preferred
D - Commercial
MPS - Dedicated
Previous VPSs
* Sign Up! *

Support
Contact Us
Online Help
Handbooks
Domain Status
Man Pages

FAQ
Virtual Servers
Pricing
Billing
Technical

Network
Facilities
Connectivity
Topology Map

Miscellaneous
Server Agreement
Year 2038
Credits
 

USA Flag

 

 

Man Pages
zlaesy.f(3) LAPACK zlaesy.f(3)

zlaesy.f -


subroutine zlaesy (A, B, C, RT1, RT2, EVSCAL, CS1, SN1)
 
ZLAESY computes the eigenvalues and eigenvectors of a 2-by-2 complex symmetric matrix.

ZLAESY computes the eigenvalues and eigenvectors of a 2-by-2 complex symmetric matrix.
Purpose:
 ZLAESY computes the eigendecomposition of a 2-by-2 symmetric matrix
    ( ( A, B );( B, C ) )
 provided the norm of the matrix of eigenvectors is larger than
 some threshold value.
RT1 is the eigenvalue of larger absolute value, and RT2 of smaller absolute value. If the eigenvectors are computed, then on return ( CS1, SN1 ) is the unit eigenvector for RT1, hence
[ CS1 SN1 ] . [ A B ] . [ CS1 -SN1 ] = [ RT1 0 ] [ -SN1 CS1 ] [ B C ] [ SN1 CS1 ] [ 0 RT2 ]
Parameters:
A
          A is COMPLEX*16
          The ( 1, 1 ) element of input matrix.
B
          B is COMPLEX*16
          The ( 1, 2 ) element of input matrix.  The ( 2, 1 ) element
          is also given by B, since the 2-by-2 matrix is symmetric.
C
          C is COMPLEX*16
          The ( 2, 2 ) element of input matrix.
RT1
          RT1 is COMPLEX*16
          The eigenvalue of larger modulus.
RT2
          RT2 is COMPLEX*16
          The eigenvalue of smaller modulus.
EVSCAL
          EVSCAL is COMPLEX*16
          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 2-by-2
          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
          CS1 is COMPLEX*16
SN1
          SN1 is COMPLEX*16
          If EVSCAL .NE. 0,  ( CS1, SN1 ) is the unit right eigenvector
          for RT1.
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
September 2012
Definition at line 116 of file zlaesy.f.

Generated automatically by Doxygen for LAPACK from the source code.
Sat Nov 16 2013 Version 3.4.2

Search for    or go to Top of page |  Section 3 |  Main Index

Powered by GSP Visit the GSP FreeBSD Man Page Interface.
Output converted with ManDoc.