clags2.f(3)

NAME
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

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