DROTM(3)

SYNOPSIS
SUBROUTINE DROTM (N, DX, INCX, DY, INCY, DPARAM)

NAME
drotm - Apply a modified Givens transformation.

LIBRARY
SLATEC (BLAS)

CATEGORY
D1A8

TYPE
DOUBLE PRECISION (SROTM-S, DROTM-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-- N number of elements in input vector(s) DX double precision vector with N elements INCX storage spacing between elements of DX DY double precision vector with N elements INCY storage spacing between elements of DY DPARAM 5-element D.P. vector. DPARAM(1) is DFLAG described below. Locations 2-5 of SPARAM contain elements of the transformation matrix H described below. --Output-- DX rotated vector (unchanged if N .LE. 0) DY rotated vector (unchanged if N .LE. 0) Apply the modified Givens transformation, H, to the 2 by N matrix (DX**T) (DY**T) , where **T indicates transpose. The elements of DX are in DX(LX+I*INCX), I = 0 to N-1, where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and similarly for DY using LY and INCY. 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). See DROTMG for a description of data storage 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)
791001 DATE WRITTEN
861211 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
920310 Corrected definition of LX in DESCRIPTION. (WRB)
920501 Reformatted the REFERENCES section. (WRB)