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## drotmg()

subroutine drotmg | ( | double precision | dd1,
|  | double precision | dd2,
|  | double precision | dx1,
|  | double precision | dy1,
|  | double precision, dimension(5) | dparam )

DROTMG

Purpose:

      !>
      !>    CONSTRUCT THE MODIFIED GIVENS TRANSFORMATION MATRIX H WHICH ZEROS
      !>    THE SECOND COMPONENT OF THE 2-VECTOR  (DSQRT(DD1)*DX1,DSQRT(DD2)*>    DY2)**T.
      !>    WITH DPARAM(1)=DFLAG, H HAS ONE OF THE FOLLOWING FORMS..
      !>
      !>    DFLAG=-1.D0     DFLAG=0.D0        DFLAG=1.D0     DFLAG=-2.D0
      !>
      !>      (DH11  DH12)    (1.D0  DH12)    (DH11  1.D0)    (1.D0  0.D0)
      !>    H=(          )    (          )    (          )    (          )
      !>      (DH21  DH22),   (DH21  1.D0),   (-1.D0 DH22),   (0.D0  1.D0).
      !>    LOCATIONS 2-4 OF DPARAM CONTAIN DH11, DH21, DH12, AND DH22
      !>    RESPECTIVELY. (VALUES OF 1.D0, -1.D0, OR 0.D0 IMPLIED BY THE
      !>    VALUE OF DPARAM(1) ARE NOT STORED IN DPARAM.)
      !>
      !>    THE VALUES OF GAMSQ AND RGAMSQ SET IN THE DATA STATEMENT MAY BE
      !>    INEXACT.  THIS IS OK AS THEY ARE ONLY USED FOR TESTING THE SIZE
      !>    OF DD1 AND DD2.  ALL ACTUAL SCALING OF DATA IS DONE USING GAM.
      !>
      !>

Parameters

  [in,out]

  DD1

      !>          DD1 is DOUBLE PRECISION
      !>

  [in,out]

  DD2

      !>          DD2 is DOUBLE PRECISION
      !>

  [in,out]

  DX1

      !>          DX1 is DOUBLE PRECISION
      !>

  [in]

  DY1

      !>          DY1 is DOUBLE PRECISION
      !>

  [out]

  DPARAM

      !>          DPARAM is DOUBLE PRECISION array, dimension (5)
      !>     DPARAM(1)=DFLAG
      !>     DPARAM(2)=DH11
      !>     DPARAM(3)=DH21
      !>     DPARAM(4)=DH12
      !>     DPARAM(5)=DH22
      !>

Author
  Univ. of Tennessee
  Univ. of California Berkeley
  Univ. of Colorado Denver
  NAG Ltd.