drot()

subroutine drot	(	integer	N,
		double precision, dimension(*)	DX,
		integer	INCX,
		double precision, dimension(*)	DY,
		integer	INCY,
		double precision	C,
		double precision	S
	)

DROT

Purpose:

    DROT applies a plane rotation.

Parameters

[in]	N	N is INTEGER number of elements in input vector(s)
[in,out]	DX	DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
[in]	INCX	INCX is INTEGER storage spacing between elements of DX
[in,out]	DY	DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
[in]	INCY	INCY is INTEGER storage spacing between elements of DY
[in]	C	C is DOUBLE PRECISION
[in]	S	S is DOUBLE PRECISION

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date

November 2017

Further Details:

     jack dongarra, linpack, 3/11/78.
     modified 12/3/93, array(1) declarations changed to array(*)

Definition at line 94 of file drot.f.

*
*  -- Reference BLAS level1 routine (version 3.8.0) --
*  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2017
*
*     .. Scalar Arguments ..
      DOUBLE PRECISION C,S
      INTEGER INCX,INCY,N
*     ..
*     .. Array Arguments ..
      DOUBLE PRECISION DX(*),DY(*)
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      DOUBLE PRECISION DTEMP
      INTEGER I,IX,IY
*     ..
      IF (n.LE.0) RETURN
      IF (incx.EQ.1 .AND. incy.EQ.1) THEN
*
*       code for both increments equal to 1
*
         DO i = 1,n
            dtemp = c*dx(i) + s*dy(i)
            dy(i) = c*dy(i) - s*dx(i)
            dx(i) = dtemp
         END DO
      ELSE
*
*       code for unequal increments or equal increments not equal
*         to 1
*
         ix = 1
         iy = 1
         IF (incx.LT.0) ix = (-n+1)*incx + 1
         IF (incy.LT.0) iy = (-n+1)*incy + 1
         DO i = 1,n
            dtemp = c*dx(ix) + s*dy(iy)
            dy(iy) = c*dy(iy) - s*dx(ix)
            dx(ix) = dtemp
            ix = ix + incx
            iy = iy + incy
         END DO
      END IF
      RETURN

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