zlags2.f man page

zlags2.f —

Synopsis

Functions/Subroutines

subroutine zlags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
ZLAGS2

Function/Subroutine Documentation

subroutine zlags2 (logicalUPPER, double precisionA1, complex*16A2, double precisionA3, double precisionB1, complex*16B2, double precisionB3, double precisionCSU, complex*16SNU, double precisionCSV, complex*16SNV, double precisionCSQ, complex*16SNQ)

ZLAGS2

Purpose:

ZLAGS2 computes 2-by-2 unitary matrices U, V and Q, such
that if ( UPPER ) then

          U**H *A*Q = U**H *( A1 A2 )*Q = ( x  0  )
                            ( 0  A3 )     ( x  x  )
and
          V**H*B*Q = V**H *( B1 B2 )*Q = ( x  0  )
                           ( 0  B3 )     ( x  x  )

or if ( .NOT.UPPER ) then

          U**H *A*Q = U**H *( A1 0  )*Q = ( x  x  )
                            ( A2 A3 )     ( 0  x  )
and
          V**H *B*Q = V**H *( B1 0  )*Q = ( x  x  )
                            ( B2 B3 )     ( 0  x  )
where

  U = (   CSU    SNU ), V = (  CSV    SNV ),
      ( -SNU**H  CSU )      ( -SNV**H CSV )

  Q = (   CSQ    SNQ )
      ( -SNQ**H  CSQ )

The rows of the transformed A and B are parallel. Moreover, if the
input 2-by-2 matrix A is not zero, then the transformed (1,1) entry
of A is not zero. If the input matrices A and B are both not zero,
then the transformed (2,2) element of B is not zero, except when the
first rows of input A and B are parallel and the second rows are
zero.

Parameters:

UPPER

UPPER is LOGICAL
= .TRUE.: the input matrices A and B are upper triangular.
= .FALSE.: the input matrices A and B are lower triangular.

A1

A1 is DOUBLE PRECISION

A2

A2 is COMPLEX*16

A3

A3 is DOUBLE PRECISION
On entry, A1, A2 and A3 are elements of the input 2-by-2
upper (lower) triangular matrix A.

B1

B1 is DOUBLE PRECISION

B2

B2 is COMPLEX*16

B3

B3 is DOUBLE PRECISION
On entry, B1, B2 and B3 are elements of the input 2-by-2
upper (lower) triangular matrix B.

CSU

CSU is DOUBLE PRECISION

SNU

SNU is COMPLEX*16
The desired unitary matrix U.

CSV

CSV is DOUBLE PRECISION

SNV

SNV is COMPLEX*16
The desired unitary matrix V.

CSQ

CSQ is DOUBLE PRECISION

SNQ

SNQ is COMPLEX*16
The desired unitary matrix Q.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 158 of file zlags2.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

zlags2(3) is an alias of zlags2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK