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SUBROUTINE ZLACRT( N, CX, INCX, CY, INCY, C, S )
*
* -- LAPACK auxiliary routine (version 3.2) --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2006
*
* .. Scalar Arguments ..
INTEGER INCX, INCY, N
COMPLEX*16 C, S
* ..
* .. Array Arguments ..
COMPLEX*16 CX( * ), CY( * )
* ..
*
* Purpose
* =======
*
* 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.
*
* Arguments
* =========
*
* N (input) INTEGER
* The number of elements in the vectors CX and CY.
*
* CX (input/output) COMPLEX*16 array, dimension (N)
* On input, the vector x.
* On output, CX is overwritten with c*x + s*y.
*
* INCX (input) INTEGER
* The increment between successive values of CX. INCX <> 0.
*
* CY (input/output) COMPLEX*16 array, dimension (N)
* On input, the vector y.
* On output, CY is overwritten with -s*x + c*y.
*
* INCY (input) INTEGER
* The increment between successive values of CY. INCY <> 0.
*
* C (input) COMPLEX*16
* S (input) COMPLEX*16
* C and S define the matrix
* [ C S ].
* [ -S C ]
*
* =====================================================================
*
* .. 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
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