d3/dc0/zswap_8f_source.html

00001       SUBROUTINE ZSWAP(N,ZX,INCX,ZY,INCY)
00002 *     .. Scalar Arguments ..
00003       INTEGER INCX,INCY,N
00004 *     ..
00005 *     .. Array Arguments ..
00006       DOUBLE COMPLEX ZX(*),ZY(*)
00007 *     ..
00008 *
00009 *  Purpose
00010 *  =======
00011 *
00012 *     ZSWAP interchanges two vectors.
00013 *
00014 *  Further Details
00015 *  ===============
00016 *
00017 *     jack dongarra, 3/11/78.
00018 *     modified 12/3/93, array(1) declarations changed to array(*)
00019 *
00020 *  =====================================================================
00021 *
00022 *     .. Local Scalars ..
00023       DOUBLE COMPLEX ZTEMP
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             ZTEMP = ZX(I)
00032             ZX(I) = ZY(I)
00033             ZY(I) = ZTEMP
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             ZTEMP = ZX(IX)
00046             ZX(IX) = ZY(IY)
00047             ZY(IY) = ZTEMP
00048             IX = IX + INCX
00049             IY = IY + INCY
00050          END DO
00051       END IF
00052       RETURN
00053       END