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*> \brief \b CSROT
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE CSROT( N, CX, INCX, CY, INCY, C, S )
*
* .. Scalar Arguments ..
* INTEGER INCX, INCY, N
* REAL C, S
* ..
* .. Array Arguments ..
* COMPLEX CX( * ), CY( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> CSROT applies a plane rotation, where the cos and sin (c and s) are real
*> and the vectors cx and cy are complex.
*> jack dongarra, linpack, 3/11/78.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> On entry, N specifies the order of the vectors cx and cy.
*> N must be at least zero.
*> \endverbatim
*>
*> \param[in,out] CX
*> \verbatim
*> CX is COMPLEX array, dimension at least
*> ( 1 + ( N - 1 )*abs( INCX ) ).
*> Before entry, the incremented array CX must contain the n
*> element vector cx. On exit, CX is overwritten by the updated
*> vector cx.
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*> INCX is INTEGER
*> On entry, INCX specifies the increment for the elements of
*> CX. INCX must not be zero.
*> \endverbatim
*>
*> \param[in,out] CY
*> \verbatim
*> CY is COMPLEX array, dimension at least
*> ( 1 + ( N - 1 )*abs( INCY ) ).
*> Before entry, the incremented array CY must contain the n
*> element vector cy. On exit, CY is overwritten by the updated
*> vector cy.
*> \endverbatim
*>
*> \param[in] INCY
*> \verbatim
*> INCY is INTEGER
*> On entry, INCY specifies the increment for the elements of
*> CY. INCY must not be zero.
*> \endverbatim
*>
*> \param[in] C
*> \verbatim
*> C is REAL
*> On entry, C specifies the cosine, cos.
*> \endverbatim
*>
*> \param[in] S
*> \verbatim
*> S is REAL
*> On entry, S specifies the sine, sin.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup complex_blas_level1
*
* =====================================================================
SUBROUTINE CSROT( N, CX, INCX, CY, INCY, C, S )
*
* -- Reference BLAS level1 routine (version 3.4.0) --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2011
*
* .. Scalar Arguments ..
INTEGER INCX, INCY, N
REAL C, S
* ..
* .. Array Arguments ..
COMPLEX CX( * ), CY( * )
* ..
*
* =====================================================================
*
* .. Local Scalars ..
INTEGER I, IX, IY
COMPLEX CTEMP
* ..
* .. Executable Statements ..
*
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
CTEMP = C*CX( I ) + S*CY( I )
CY( I ) = C*CY( I ) - S*CX( I )
CX( I ) = CTEMP
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
CTEMP = C*CX( IX ) + S*CY( IY )
CY( IY ) = C*CY( IY ) - S*CX( IX )
CX( IX ) = CTEMP
IX = IX + INCX
IY = IY + INCY
END DO
END IF
RETURN
END
|
