clags2.f man page

clags2.f —

Synopsis

Functions/Subroutines

subroutine clags2 (UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV, CSQ, SNQ)
CLAGS2

Function/Subroutine Documentation

subroutine clags2 (logicalUPPER, realA1, complexA2, realA3, realB1, complexB2, realB3, realCSU, complexSNU, realCSV, complexSNV, realCSQ, complexSNQ)

CLAGS2

Purpose:

CLAGS2 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 REAL

A2

A2 is COMPLEX

A3

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

B1

B1 is REAL

B2

B2 is COMPLEX

B3

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

CSU

CSU is REAL

SNU

SNU is COMPLEX
The desired unitary matrix U.

CSV

CSV is REAL

SNV

SNV is COMPLEX
The desired unitary matrix V.

CSQ

CSQ is REAL

SNQ

SNQ is COMPLEX
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 clags2.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

clags2(3) is an alias of clags2.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK