SRC/clags2.f(3)

NAME
SRC/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 (logical upper, real a1, complex a2, real a3, real b1, complex b2, real b3, real csu, complex snu, real csv, complex snv, real csq, complex snq)

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.

Definition at line 156 of file clags2.f.

Author

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