The direct difference is very fast, but it has a certain cost to set up, and it can accumulate an error when you step along the curve. If you use double precision floats, you donβt need to worry about the error, but if you use a fixed point or integers, this can be significant.
In my experience, the cost of a direct difference setting is only for more than 2 * (N + 1) estimates; therefore, for (say) a cubic curve, if you need less than eight points on the curve, you better just evaluate the curve straight eight times using the formula in the original message.
Note that the formula is actually pretty fast if you expand the polynomials and collect terms for commonly used N values.
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