SRC/slags2.f(3)

NAME
SRC/slags2.f

SYNOPSIS

  Functions/Subroutines
subroutine slags2 (upper, a1, a2, a3, b1, b2, b3, csu, snu, csv, snv, csq, snq)
SLAGS2 computes 2-by-2 orthogonal matrices U, V, and Q, and applies them to matrices A and B such that the rows of the transformed A and B are parallel.

Function/Subroutine Documentation

  subroutine slags2 (logical upper, real a1, real a2, real a3, real b1, real b2, real b3, real csu, real snu, real csv, real snv, real csq, real snq)

SLAGS2 computes 2-by-2 orthogonal matrices U, V, and Q, and applies them to matrices A and B such that the rows of the transformed A and B are parallel.

Purpose:

    !>
    !> SLAGS2 computes 2-by-2 orthogonal matrices U, V and Q, such
    !> that if ( UPPER ) then
    !>
    !>           U**T *A*Q = U**T *( A1 A2 )*Q = ( x  0  )
    !>                             ( 0  A3 )     ( x  x  )
    !> and
    !>           V**T*B*Q = V**T *( B1 B2 )*Q = ( x  0  )
    !>                            ( 0  B3 )     ( x  x  )
    !>
    !> or if ( .NOT.UPPER ) then
    !>
    !>           U**T *A*Q = U**T *( A1 0  )*Q = ( x  x  )
    !>                             ( A2 A3 )     ( 0  x  )
    !> and
    !>           V**T*B*Q = V**T*( B1 0  )*Q = ( x  x  )
    !>                           ( B2 B3 )     ( 0  x  )
    !>
    !> The rows of the transformed A and B are parallel, where
    !>
    !>   U = (  CSU  SNU ), V = (  CSV SNV ), Q = (  CSQ   SNQ )
    !>       ( -SNU  CSU )      ( -SNV CSV )      ( -SNQ   CSQ )
    !>
    !> Z**T denotes the transpose of Z.
    !>
    !>

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 REAL
    !>

    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 REAL
    !>

    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 REAL
    !>          The desired orthogonal matrix U.
    !>

    CSV

    !>          CSV is REAL
    !>

    SNV

    !>          SNV is REAL
    !>          The desired orthogonal matrix V.
    !>

    CSQ

    !>          CSQ is REAL
    !>

    SNQ

    !>          SNQ is REAL
    !>          The desired orthogonal matrix Q.
    !>

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 150 of file slags2.f.

Author

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