 
      SUBROUTINE DROT(N,DX,INCX,DY,INCY,DC,DS)
C***BEGIN PROLOGUE  DROT
C***DATE WRITTEN   791001   (YYMMDD)
C***REVISION DATE  820801   (YYMMDD)
C***CATEGORY NO.  D1A8
C***KEYWORDS  BLAS,GIVENS ROTATION,LINEAR ALGEBRA,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***PURPOSE  APPLY d.p. Givens rotation
C***DESCRIPTION
C
C                B L A S  Subprogram
C    Description of Parameters
C
C     --Input--
C        N  number of elements in input vector(s)
C       DX  double precision vector with N elements
C     INCX  storage spacing between elements of DX
C       DY  double precision vector with N elements
C     INCY  storage spacing between elements of DY
C       DC  D.P. element of rotation matrix
C       DS  D.P. element of rotation matrix
C
C     --Output--
C       DX  rotated vector (unchanged if N .LE. 0)
C       DY  rotated vector (unchanged if N .LE. 0)
C
C     Multiply the 2 X 2 matrix  ( DC DS) times the 2 X N matrix (DX**T)
C                                (-DS DC)                        (DY**T)
C     where **T indicates transpose.  The elements of DX are in
C     DX(LX+I*INCX), I = 0 to N-1, where LX = 1 if INCX .GE. 0, else
C     LX = (-INCX)*N, and similarly for DY using LY and INCY.
C***REFERENCES  LAWSON C.L., HANSON R.J., KINCAID D.R., KROGH F.T.,
C                 *BASIC LINEAR ALGEBRA SUBPROGRAMS FOR FORTRAN USAGE*,
C                 ALGORITHM NO. 539, TRANSACTIONS ON MATHEMATICAL
C                 SOFTWARE, VOLUME 5, NUMBER 3, SEPTEMBER 1979, 308-323
C***ROUTINES CALLED  (NONE)
C***END PROLOGUE  DROT
 
 
