2 comments

  • krackers2 hours ago
    Is there any good writeup yet of intuitively where the speedup comes from? E.g. with fast fourier transform you can see that there's a lot of symmetry & recomputation in the Vandermonde matrix, so that's where the speed up comes from.
    • AnotherGoodName53 minutes ago
      The site is taking forever to load but complexity theory doesn&#x27;t really have the hard walls at things like O(nlogn) that people seem to think.<p>You can always always tradeoff time vs space. It&#x27;s actually a fundamental part of complexity theory called Blums speedup theorem by the guy who invented complexity theory no less.<p>As an example you give me an nlogn solution and i take a portion of the inner loop, put it in a lookup table (who cares if the lookup table is 2^n in size, that&#x27;s not what we&#x27;re measuring here since we&#x27;re specifically measuring time not space) and suddenly i have something better than nlogn since that lookup table is O(1).<p>That&#x27;s not to say there&#x27;s some merit to all of this. It&#x27;s just that people shouldn&#x27;t be as astonished by these results as they are. It&#x27;s complexity theory. There&#x27;s literally no such thing as a hard wall where something is nlogn in time and can&#x27;t get lower. It can always get lower. But you need both the time and space complexities together to reason about this.
      • cma45 minutes ago
        Wouldn&#x27;t it take an infinite lookup table to do this satisfying any two integers and still get an order-complexity speedup? The integers can be any size. You can&#x27;t specify an arbitrarily variable sized lookup table in the normal formulation of these problems without computing the lookup table as part of the computation.
        • AnotherGoodName37 minutes ago
          Never infinite if you have bounds on integer size. For n bits of input it&#x27;s always possible to have a 2^n space complexity lookup table that&#x27;s O(1) speed since 2^n covers all possibilities of n bits.<p>You don&#x27;t need to go to these extremes regardless though. For small speedups take an nlogn algorithm and just move a very small part of the inner portion out in a similar tradeoff. Eg. &quot;Every nth input is now part of a lookup.&quot; If you look at the openAIs &lt;nlogn results there was a series of small improvements of this type (we take this part out, precomputing it, and likewise with this part and that small portion, aha! &lt;nlogn!). I finally loaded the link above and it&#x27;s 262million lines of such tricks in fact.
  • oliculipolicula3 hours ago
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    • ViscountPenguin1 hour ago
      Huh, apparently I &quot;look like a bot&quot;. Must be my sick-as apm.