db/d2d/zdotu_8f_source.html

00001       DOUBLE COMPLEX FUNCTION ZDOTU(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 *     ZDOTU forms the dot product of 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       ZTEMP = (0.0d0,0.0d0)
00027       ZDOTU = (0.0d0,0.0d0)
00028       IF (N.LE.0) RETURN
00029       IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
00030 *
00031 *        code for unequal increments or equal increments
00032 *          not equal to 1
00033 *
00034       IX = 1
00035       IY = 1
00036       IF (INCX.LT.0) IX = (-N+1)*INCX + 1
00037       IF (INCY.LT.0) IY = (-N+1)*INCY + 1
00038       DO 10 I = 1,N
00039           ZTEMP = ZTEMP + ZX(IX)*ZY(IY)
00040           IX = IX + INCX
00041           IY = IY + INCY
00042    10 CONTINUE
00043       ZDOTU = ZTEMP
00044       RETURN
00045 *
00046 *        code for both increments equal to 1
00047 *
00048    20 DO 30 I = 1,N
00049           ZTEMP = ZTEMP + ZX(I)*ZY(I)
00050    30 CONTINUE
00051       ZDOTU = ZTEMP
00052       RETURN
00053       END