7 ms·

See the "Labor of Division" blog posts by the author of libdivide: https://ridiculousfish.com/blog/posts/labor-of-division-episode-i.html https://ridiculousfis

• joe_the_user 5y ago
  So basically calculating the multiplicative inverse of a number and storing it as something like a float (digits + exponent) with the digits and exponent stored separately to avoid overflow, underflow, accuracy issues. And it's faster if and only if you're repeating division by a single number since you're still doing the equivalent of divide to get the invest (but repeated division is actually quite common so this is useful).
  • yakubin 5y ago
    > And it's faster if and only if you're repeating division by a single number since you're still doing the equivalent of divide to get the invest This is done at compile-time by the compiler. We're talking about division by a constant, not by a variable. So it's always faster.
    • joe_the_user 5y ago
      Doing compile time is one way it is useful and I think that's the most common thing - that's why the tutorials show the resulting assembly instructions. However there are other ways the trick can be used. If the compiler (or the programmer) determines that the program will be doing repeated division by a single quantity (say in a loop), you substitution a calculation of the multiplicative inverse of the quantity first and then substitute multiplication by that inverse for the repeated for the divisions. So you can extend things beyond just division by a constant.