SUBROUTINE CSROT( N, CX, INCX, CY, INCY, C, S ) * * .. Scalar Arguments .. INTEGER INCX, INCY, N REAL C, S * .. * .. Array Arguments .. COMPLEX CX( * ), CY( * ) * .. * * Purpose * ======= * * 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. * * 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 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 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) REAL * On entry, C specifies the cosine, cos. * Unchanged on exit. * * S (input) REAL * On entry, S specifies the sine, sin. * Unchanged on exit. * * ===================================================================== * * .. 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