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*> \brief \b ZROT applies a plane rotation with real cosine and complex sine to a pair of complex vectors.
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download ZROT + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zrot.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zrot.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zrot.f">
*> [TXT]</a>
*> \endhtmlonly
*
* Definition:
* ===========
*
* SUBROUTINE ZROT( N, CX, INCX, CY, INCY, C, S )
*
* .. Scalar Arguments ..
* INTEGER INCX, INCY, N
* DOUBLE PRECISION C
* COMPLEX*16 S
* ..
* .. Array Arguments ..
* COMPLEX*16 CX( * ), CY( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> ZROT applies a plane rotation, where the cos (C) is real and the
*> sin (S) is complex, and the vectors CX and CY are complex.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \param[in] N
*> \verbatim
*> N is INTEGER
*> The number of elements in the vectors CX and CY.
*> \endverbatim
*>
*> \param[in,out] CX
*> \verbatim
*> CX is COMPLEX*16 array, dimension (N)
*> On input, the vector X.
*> On output, CX is overwritten with C*X + S*Y.
*> \endverbatim
*>
*> \param[in] INCX
*> \verbatim
*> INCX is INTEGER
*> The increment between successive values of CY. INCX <> 0.
*> \endverbatim
*>
*> \param[in,out] CY
*> \verbatim
*> CY is COMPLEX*16 array, dimension (N)
*> On input, the vector Y.
*> On output, CY is overwritten with -CONJG(S)*X + C*Y.
*> \endverbatim
*>
*> \param[in] INCY
*> \verbatim
*> INCY is INTEGER
*> The increment between successive values of CY. INCX <> 0.
*> \endverbatim
*>
*> \param[in] C
*> \verbatim
*> C is DOUBLE PRECISION
*> \endverbatim
*>
*> \param[in] S
*> \verbatim
*> S is COMPLEX*16
*> C and S define a rotation
*> [ C S ]
*> [ -conjg(S) C ]
*> where C*C + S*CONJG(S) = 1.0.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date December 2016
*
*> \ingroup complex16OTHERauxiliary
*
* =====================================================================
SUBROUTINE ZROT( N, CX, INCX, CY, INCY, C, S )
*
* -- LAPACK auxiliary routine (version 3.7.0) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* December 2016
*
* .. Scalar Arguments ..
INTEGER INCX, INCY, N
DOUBLE PRECISION C
COMPLEX*16 S
* ..
* .. Array Arguments ..
COMPLEX*16 CX( * ), CY( * )
* ..
*
* =====================================================================
*
* .. Local Scalars ..
INTEGER I, IX, IY
COMPLEX*16 STEMP
* ..
* .. Intrinsic Functions ..
INTRINSIC DCONJG
* ..
* .. Executable Statements ..
*
IF( N.LE.0 )
$ RETURN
IF( INCX.EQ.1 .AND. INCY.EQ.1 )
$ GO TO 20
*
* 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 10 I = 1, N
STEMP = C*CX( IX ) + S*CY( IY )
CY( IY ) = C*CY( IY ) - DCONJG( S )*CX( IX )
CX( IX ) = STEMP
IX = IX + INCX
IY = IY + INCY
10 CONTINUE
RETURN
*
* Code for both increments equal to 1
*
20 CONTINUE
DO 30 I = 1, N
STEMP = C*CX( I ) + S*CY( I )
CY( I ) = C*CY( I ) - DCONJG( S )*CX( I )
CX( I ) = STEMP
30 CONTINUE
RETURN
END
|
