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How do you compute the reciprocal without division? A precomputed lookup table?
by ficklepickle 6y ago
How do you compute the reciprocal without division? A precomputed lookup table?
- variaga 6y agoNewton-Rapheson method to calculate X = 1/D 1) Make a guess at the reciprocal X(0) (this can come from a small LUT, but a static "guess" can also work) 2) Calculate an improved reciprocal X(n) iteratively using the relation: X(i+1) = X(i)*(2-X(i)*D) Repeat (2) until X(i) is accurate "enough". This is relatively fast, since the # of correct bits in X() doubles for each iteration. There are several other methods: https://en.wikipedia.org/wiki/Division_algorithm#Fast_division_methods https://en.wikipedia.org/wiki/Division_algorithm#Fast_divisi...