DOUBLE PRECISION FUNCTION DDOT(N,DX,INCX,DY,INCY)
* .. Scalar Arguments ..
INTEGER INCX,INCY,N
* ..
* .. Array Arguments ..
DOUBLE PRECISION DX(*),DY(*)
* ..
*
* Purpose
* =======
*
* forms the dot product of two vectors.
* uses unrolled loops for increments equal to one.
* jack dongarra, linpack, 3/11/78.
* modified 12/3/93, array(1) declarations changed to array(*)
*
*
* .. Local Scalars ..
DOUBLE PRECISION DTEMP
INTEGER I,IX,IY,M,MP1
* ..
* .. Intrinsic Functions ..
INTRINSIC MOD
* ..
DDOT = 0.0d0
DTEMP = 0.0d0
IF (N.LE.0) RETURN
IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
*
* 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 10 I = 1,N
DTEMP = DTEMP + DX(IX)*DY(IY)
IX = IX + INCX
IY = IY + INCY
10 CONTINUE
DDOT = DTEMP
RETURN
*
* code for both increments equal to 1
*
*
* clean-up loop
*
20 M = MOD(N,5)
IF (M.EQ.0) GO TO 40
DO 30 I = 1,M
DTEMP = DTEMP + DX(I)*DY(I)
30 CONTINUE
IF (N.LT.5) GO TO 60
40 MP1 = M + 1
DO 50 I = MP1,N,5
DTEMP = DTEMP + DX(I)*DY(I) + DX(I+1)*DY(I+1) +
+ DX(I+2)*DY(I+2) + DX(I+3)*DY(I+3) + DX(I+4)*DY(I+4)
50 CONTINUE
60 DDOT = DTEMP
RETURN
END