dd/db2/cdotc_8f_source.html

00001       COMPLEX FUNCTION CDOTC(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 *     forms the dot product of two vectors, conjugating the first
00013 *     vector.
00014 *
00015 *  Further Details
00016 *  ===============
00017 *
00018 *     jack dongarra, linpack,  3/11/78.
00019 *     modified 12/3/93, array(1) declarations changed to array(*)
00020 *
00021 *  =====================================================================
00022 *
00023 *     .. Local Scalars ..
00024       COMPLEX CTEMP
00025       INTEGER I,IX,IY
00026 *     ..
00027 *     .. Intrinsic Functions ..
00028       INTRINSIC CONJG
00029 *     ..
00030       CTEMP = (0.0,0.0)
00031       CDOTC = (0.0,0.0)
00032       IF (N.LE.0) RETURN
00033       IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
00034 *
00035 *        code for unequal increments or equal increments
00036 *          not equal to 1
00037 *
00038       IX = 1
00039       IY = 1
00040       IF (INCX.LT.0) IX = (-N+1)*INCX + 1
00041       IF (INCY.LT.0) IY = (-N+1)*INCY + 1
00042       DO 10 I = 1,N
00043           CTEMP = CTEMP + CONJG(CX(IX))*CY(IY)
00044           IX = IX + INCX
00045           IY = IY + INCY
00046    10 CONTINUE
00047       CDOTC = CTEMP
00048       RETURN
00049 *
00050 *        code for both increments equal to 1
00051 *
00052    20 DO 30 I = 1,N
00053           CTEMP = CTEMP + CONJG(CX(I))*CY(I)
00054    30 CONTINUE
00055       CDOTC = CTEMP
00056       RETURN
00057       END