d1/d44/cswap_8f_source.html

00001       SUBROUTINE CSWAP(N,CX,INCX,CY,INCY)
00002 *     .. Scalar Arguments ..
00003       INTEGER INCX,INCY,N
00004 *     ..
00005 *     .. Array Arguments ..
00006       COMPLEX CX(*),CY(*)
00007 *     ..
00008 *
00009 *  Purpose
00010 *  =======
00011 *
00012 *    CSWAP interchanges two vectors.
00013 *
00014 *  Further Details
00015 *  ===============
00016 *
00017 *     jack dongarra, linpack, 3/11/78.
00018 *     modified 12/3/93, array(1) declarations changed to array(*)
00019 *
00020 *  =====================================================================
00021 *
00022 *     .. Local Scalars ..
00023       COMPLEX CTEMP
00024       INTEGER I,IX,IY
00025 *     ..
00026       IF (N.LE.0) RETURN
00027       IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
00028 *
00029 *       code for both increments equal to 1
00030          DO I = 1,N
00031             CTEMP = CX(I)
00032             CX(I) = CY(I)
00033             CY(I) = CTEMP
00034          END DO
00035       ELSE
00036 *
00037 *       code for unequal increments or equal increments not equal
00038 *         to 1
00039 *
00040          IX = 1
00041          IY = 1
00042          IF (INCX.LT.0) IX = (-N+1)*INCX + 1
00043          IF (INCY.LT.0) IY = (-N+1)*INCY + 1
00044          DO I = 1,N
00045             CTEMP = CX(IX)
00046             CX(IX) = CY(IY)
00047             CY(IY) = CTEMP
00048             IX = IX + INCX
00049             IY = IY + INCY
00050          END DO
00051       END IF
00052       RETURN
00053       END