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SUBROUTINE ZDROT( N, CX, INCX, CY, INCY, C, S )
*
* .. Scalar Arguments ..
INTEGER INCX, INCY, N
DOUBLE PRECISION C, S
* ..
* .. Array Arguments ..
COMPLEX*16 CX( * ), CY( * )
* ..
*
* Purpose
* =======
*
* 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.
*
* Arguments
* ==========
*
* N (input) INTEGER
* On entry, N specifies the order of the vectors cx and cy.
* N must be at least zero.
* Unchanged on exit.
*
* CX (input) COMPLEX*16 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.
*
* INCX (input) INTEGER
* On entry, INCX specifies the increment for the elements of
* CX. INCX must not be zero.
* Unchanged on exit.
*
* CY (input) COMPLEX*16 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.
*
* INCY (input) INTEGER
* On entry, INCY specifies the increment for the elements of
* CY. INCY must not be zero.
* Unchanged on exit.
*
* C (input) DOUBLE PRECISION
* On entry, C specifies the cosine, cos.
* Unchanged on exit.
*
* S (input) DOUBLE PRECISION
* On entry, S specifies the sine, sin.
* Unchanged on exit.
*
* =====================================================================
*
* .. Local Scalars ..
INTEGER I, IX, IY
COMPLEX*16 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
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