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*> \brief \b ZLACRT
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download ZLACRT + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zlacrt.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zlacrt.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zlacrt.f">
*> [TXT]</a>
*> \endhtmlonly
*
* Definition:
* ===========
*
* SUBROUTINE ZLACRT( N, CX, INCX, CY, INCY, C, S )
*
* .. Scalar Arguments ..
* INTEGER INCX, INCY, N
* COMPLEX*16 C, S
* ..
* .. Array Arguments ..
* COMPLEX*16 CX( * ), CY( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> ZLACRT performs the operation
*>
*> ( c s )( x ) ==> ( x )
*> ( -s c )( y ) ( y )
*>
*> where c and s are complex and the vectors x and y 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 CX. 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 -s*x + c*y.
*> \endverbatim
*>
*> \param[in] INCY
*> \verbatim
*> INCY is INTEGER
*> The increment between successive values of CY. INCY <> 0.
*> \endverbatim
*>
*> \param[in] C
*> \verbatim
*> C is COMPLEX*16
*> \endverbatim
*>
*> \param[in] S
*> \verbatim
*> S is COMPLEX*16
*> C and S define the matrix
*> [ C S ].
*> [ -S C ]
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup complex16OTHERauxiliary
*
* =====================================================================
SUBROUTINE ZLACRT( N, CX, INCX, CY, INCY, C, S )
*
* -- LAPACK auxiliary routine (version 3.4.0) --
* -- LAPACK 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
COMPLEX*16 C, S
* ..
* .. Array Arguments ..
COMPLEX*16 CX( * ), CY( * )
* ..
*
* =====================================================================
*
* .. Local Scalars ..
INTEGER I, IX, IY
COMPLEX*16 CTEMP
* ..
* .. 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
CTEMP = C*CX( IX ) + S*CY( IY )
CY( IY ) = C*CY( IY ) - S*CX( IX )
CX( IX ) = CTEMP
IX = IX + INCX
IY = IY + INCY
10 CONTINUE
RETURN
*
* Code for both increments equal to 1
*
20 CONTINUE
DO 30 I = 1, N
CTEMP = C*CX( I ) + S*CY( I )
CY( I ) = C*CY( I ) - S*CX( I )
CX( I ) = CTEMP
30 CONTINUE
RETURN
END
|
