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dlags2

 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 tri-
              angular.
              = .FALSE.: the input matrices A and B are lower tri-
              angular.

      A1      (input) DOUBLE PRECISION
              A2      (input) DOUBLE PRECISION A3      (input)
              DOUBLE PRECISION On entry, A1, A2 and A3 are entries
              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 entries
              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.