dlags2(3F)

NAME
     DLAGS2 - compute 2-by-2 orthogonal matrices U, V and Q, such that if (
     UPPER ) then   U'*A*Q = U'*( A1 A2 )*Q = ( x 0 )  ( 0 A3 ) ( x x ) and
     V'*B*Q = V'*( B1 B2 )*Q = ( x 0 )  ( 0 B3 ) ( x x )  or if ( .NOT.UPPER )
     then   U'*A*Q = U'*( A1 0 )*Q = ( x x )  ( A2 A3 ) ( 0 x ) and  V'*B*Q =
     V'*( 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' denotes the transpose
     of Z

SYNOPSIS
     SUBROUTINE DLAGS2( UPPER, A1, A2, A3, B1, B2, B3, CSU, SNU, CSV, SNV,
                        CSQ, SNQ )

         LOGICAL        UPPER

         DOUBLE         PRECISION A1, A2, A3, B1, B2, B3, CSQ, CSU, CSV, SNQ,
                        SNU, SNV

PURPOSE
     DLAGS2 computes 2-by-2 orthogonal matrices U, V and Q, such that if (
     UPPER ) then



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

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

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

     CSU     (output) DOUBLE PRECISION
             SNU     (output) DOUBLE PRECISION The desired orthogonal matrix
             U.

     CSV     (output) DOUBLE PRECISION
             SNV     (output) DOUBLE PRECISION The desired orthogonal matrix
             V.

     CSQ     (output) DOUBLE PRECISION
             SNQ     (output) DOUBLE PRECISION The desired orthogonal matrix
             Q.