The Third Hard Problem

(mmapped.blog)

32 points | by surprisetalk 3 days ago ago

21 comments

  • chaboud 2 hours ago

    The problem with trees is that the are a dimensional reduction, an aggregation; taking a problem without directionality and applying a useful/functional hierarchy.

    And that's a problem because Aggregability is NP-Hard: https://dl.acm.org/doi/abs/10.1145/1165555.1165556

    So a tree is a way to take a high dimensionality graph and make it usefully lower dimensionality, but, given the aforementioned proof, that reduction is going to go from being a lossless compression to a heuristic. So any interesting problem (at least, any problem interesting to me) is only going to be aided (read: not solved exhaustively) by that hierarchy.

    I'm okay with this. Being okay with this has been one of the most freeing things over the last 20 years of my career. Accept inaccuracy, and find usefulness in your data structures.

  • petersumskas 5 minutes ago

    There are only two hard problems in computer programming:

    1. Naming things 2. Cache invalidation 3. off-by-one errors

    • sprayk 2 minutes ago

      there are actually 10 problems: naming things, cache invalidation, base conversions, off by one errors, and cache invalidation

  • et1337 2 hours ago

    I think all three problems are really one problem under the hood:

    Are these two things actually the same thing, or they separate?

    • tikhonj 2 hours ago

      Reminds me of my favorite math essay: "When is one thing equal to some other thing?"

      It's a great question, much deeper and more interesting than it seems. The essay suggests thinking in terms of isomorphisms (relative to the structure you care about) rather than equality in some absolute sense, and I've found a fuzzy version of that to be a really useful perspective even in areas that can't be fully formalized.

      https://people.math.osu.edu/cogdell.1/6112-Mazur-www.pdf

    • hackthemack an hour ago

      I jumped to a similar conclusion right away and popped over here to comment only to find you have beaten me to the punch. I use to keep a work wiki page of common problems the team encounters over and over again.

      Years ago, I stumbled upon the "idea" was already debated in other fields long before programming. Lumpers and Splitters.

      https://en.wikipedia.org/wiki/Lumpers_and_splitters

    • hexasquid an hour ago

      "Ambiguity is the enemy", as a rule of thumb, has helped me

    • aleksiy123 2 hours ago

      Or non binary. How much are these the same and how.

  • evmar an hour ago

    One nice tool for analyzing maps as a tree is as a dominator trees. I wrote a bit about it here: https://neugierig.org/software/blog/2023/07/dominator.html

  • mcphage 3 hours ago

    I thought the two hard problems were naming things, cache invalidation, and off-by-one errors?

    • rectang an hour ago

      At least the title “The Third Hard Problem” is still appropriate regardless of whether you get the joke right.

    • fragmede 2 hours ago

      Don't race forget conditions!

      • cheschire an hour ago

        His message was submitted before the memory recall completed execution.

  • ToniDoni 2 hours ago

    I thought it was timezones.

  • kator 2 hours ago

    I wonder whether the author deliberately avoided ontology? That's what comes to mind when I read this. The age-old debate between taxonomy and ontology.

  • jeffbee an hour ago

    The first chapter of this waves away the fact that hierarchical filesystems are now useless, but it is still a fact. There is no more reason to organize your files than there is to drive around in a chariot. It is hard to map one domain to the other, but it is also not necessary. With AI indexing and recall it's less necessary than it has ever been.

    • g8oz an hour ago

      This seems optimistic.

  • Svoka an hour ago

    Putting object into trees is basically a caching problem.

    • recursivecaveat an hour ago

      I was thinking it's a naming problem haha, a file path can be seen as a global/fully-qualified name really.

  • aleksiy123 2 hours ago

    Use multiple trees.

  • adampunk 3 hours ago

    This is more true as stated than people want to give credit for, usually.