srot.f

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*> \brief \b SROT
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*  Definition:
*  ===========
*
*       SUBROUTINE SROT(N,SX,INCX,SY,INCY,C,S)
*
*       .. Scalar Arguments ..
*       REAL C,S
*       INTEGER INCX,INCY,N
*       ..
*       .. Array Arguments ..
*       REAL SX(*),SY(*)
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*>    applies a plane rotation.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] N
*> \verbatim
*>          N is INTEGER
*>         number of elements in input vector(s)
*> \endverbatim
*>
*> \param[in,out] SX
*> \verbatim
*>          SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*>          INCX is INTEGER
*>         storage spacing between elements of SX
*> \endverbatim
*>
*> \param[in,out] SY
*> \verbatim
*>          SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
*> \endverbatim
*>
*> \param[in] INCY
*> \verbatim
*>          INCY is INTEGER
*>         storage spacing between elements of SY
*> \endverbatim
*>
*> \param[in] C
*> \verbatim
*>          C is REAL
*> \endverbatim
*>
*> \param[in] S
*> \verbatim
*>          S is REAL
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup rot
*
*> \par Further Details:
*  =====================
*>
*> \verbatim
*>
*>     jack dongarra, linpack, 3/11/78.
*>     modified 12/3/93, array(1) declarations changed to array(*)
*> \endverbatim
*>
*  =====================================================================
      SUBROUTINE srot(N,SX,INCX,SY,INCY,C,S)
*
*  -- Reference BLAS level1 routine --
*  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      REAL C,S
      INTEGER INCX,INCY,N
*     ..
*     .. Array Arguments ..
      REAL SX(*),SY(*)
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      REAL STEMP
      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
            stemp = c*sx(i) + s*sy(i)
            sy(i) = c*sy(i) - s*sx(i)
            sx(i) = stemp
         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
            stemp = c*sx(ix) + s*sy(iy)
            sy(iy) = c*sy(iy) - s*sx(ix)
            sx(ix) = stemp
            ix = ix + incx
            iy = iy + incy
         END DO
      END IF
      RETURN
*
*     End of SROT
*
      END