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Caculating 1/d if you have multiply

  1. Apr 18, 2007 #1


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    This will be done in assembly code, using an integer multiply, 32 bit by 32 bit producing 64 bit result. Unsigned algorithm is good enough.

    Generic algorithm to find 1 / D, eq is initial estimated quotient, from table, say with 8 bits of precision.

    [tex] q_0\ =\ eq[/tex]

    [tex] q_{n+1}\ =\ q_n\ (2\ -\ q_n\ X)[/tex]

    For integer math, pre and post shifting of values will be done. Generally only 4 or 5 interations are required to get 32 bits of precision.

    Are there better algorithms?
    Last edited: Apr 18, 2007
  2. jcsd
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