DROTMG(3)

SYNOPSIS
SUBROUTINE DROTMG (DD1, DD2, DX1, DY1, DPARAM)

NAME
drotmg - Construct a modified Givens transformation.

LIBRARY
SLATEC (BLAS)

CATEGORY
D1B10

TYPE
DOUBLE PRECISION (SROTMG-S, DROTMG-D)

KEYWORDS
BLAS, LINEAR ALGEBRA, MODIFIED GIVENS ROTATION, VECTOR

AUTHOR
Lawson, C. L., (JPL) Hanson, R. J., (SNLA) Kincaid, D. R., (U. of Texas) Krogh, F. T., (JPL)

DESCRIPTION
B L A S Subprogram Description of Parameters --Input-- DD1 double precision scalar DD2 double precision scalar DX1 double precision scalar DX2 double precision scalar DPARAM D.P. 5-vector. DPARAM(1)=DFLAG defined below. Locations 2-5 contain the rotation matrix. --Output-- DD1 changed to represent the effect of the transformation DD2 changed to represent the effect of the transformation DX1 changed to represent the effect of the transformation DX2 unchanged Construct the modified Givens transformation matrix H which zeros the second component of the 2-vector (SQRT(DD1)*DX1,SQRT(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 2-5 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.)

REFERENCES
C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T. Krogh, Basic linear algebra subprograms for Fortran usage, Algorithm No. 539, Transactions on Mathematical Software 5, 3 (September 1979), pp. 308-323.

ROUTINES CALLED
(NONE)

REVISION HISTORY (YYMMDD)
780301 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
890531 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
920316 Prologue corrected. (WRB)
920501 Reformatted the REFERENCES section. (WRB)