DOUBLE PRECISION FUNCTION DDOT(N,SX,INCX,SY,INCY)
 
computes the inner (dot) product of two vectors.
DDOT = SUM(I=1 to N) of SX(I)*SY(I).
 
N      Input, INTEGER N, number of elements in the vectors.
 
SX     Input, DOUBLE PRECISION SX(N), vector operand.
 
INCX   Input, INTEGER INCX, increment between elements of SX.  For contiguous
       elements, INCX = 1.
 
SY     Input, DOUBLE PRECISION SY(N), vector operand.
 
INCY   Input, INTEGER INCY, increment between elements of SY.  For contiguous
       elements, INCY = 1.
 
DDOT   Output, DOUBLE PRECISION DDOT, the dot product of SX and SY.