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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



     #include <sunperf.h>

     void dlags2(int upper, double a1, double a2, double a3, dou-
               ble  b1, double b2, double b3, double *csu, double
               *snu, double *csv, double *snv, double *csq,  dou-
               ble *snq);

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 ele-
               ments 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 ele-
               ments 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.

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