Note: this is a BLAS routine and is not in libslatec.a
*DECK DROTMG
SUBROUTINE DROTMG (DD1, DD2, DX1, DY1, DPARAM)
C***BEGIN PROLOGUE DROTMG
C***PURPOSE Construct a modified Givens transformation.
C***LIBRARY SLATEC (BLAS)
C***CATEGORY D1B10
C***TYPE DOUBLE PRECISION (SROTMG-S, DROTMG-D)
C***KEYWORDS BLAS, LINEAR ALGEBRA, MODIFIED GIVENS ROTATION, VECTOR
C***AUTHOR Lawson, C. L., (JPL)
C Hanson, R. J., (SNLA)
C Kincaid, D. R., (U. of Texas)
C Krogh, F. T., (JPL)
C***DESCRIPTION
C
C B L A S Subprogram
C Description of Parameters
C
C --Input--
C DD1 double precision scalar
C DD2 double precision scalar
C DX1 double precision scalar
C DX2 double precision scalar
C DPARAM D.P. 5-vector. DPARAM(1)=DFLAG defined below.
C Locations 2-5 contain the rotation matrix.
C
C --Output--
C DD1 changed to represent the effect of the transformation
C DD2 changed to represent the effect of the transformation
C DX1 changed to represent the effect of the transformation
C DX2 unchanged
C
C Construct the modified Givens transformation matrix H which zeros
C the second component of the 2-vector (SQRT(DD1)*DX1,SQRT(DD2)*
C DY2)**T.
C With DPARAM(1)=DFLAG, H has one of the following forms:
C
C DFLAG=-1.D0 DFLAG=0.D0 DFLAG=1.D0 DFLAG=-2.D0
C
C (DH11 DH12) (1.D0 DH12) (DH11 1.D0) (1.D0 0.D0)
C H=( ) ( ) ( ) ( )
C (DH21 DH22), (DH21 1.D0), (-1.D0 DH22), (0.D0 1.D0).
C
C Locations 2-5 of DPARAM contain DH11, DH21, DH12, and DH22,
C respectively. (Values of 1.D0, -1.D0, or 0.D0 implied by the
C value of DPARAM(1) are not stored in DPARAM.)
C
C***REFERENCES C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T.
C Krogh, Basic linear algebra subprograms for Fortran
C usage, Algorithm No. 539, Transactions on Mathematical
C Software 5, 3 (September 1979), pp. 308-323.
C***ROUTINES CALLED (NONE)
C***REVISION HISTORY (YYMMDD)
C 780301 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890531 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 920316 Prologue corrected. (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE DROTMG