4 ms·

That doesn't seem rit to me. There's lots of adaptations that could probably increase fitness of offspring as a function of the parent's environment. In the sam

by rflrob 13y ago

That doesn't seem rit to me. There's lots of adaptations that could probably increase fitness of offspring as a function of the parent's environment. In the same way, you can look at some programs and predict whether they halt, just not all programs, and potentially not even all "interesting" programs, for some definition of interesting.

XorNot 13y ago
You contradict your own point though: yes, we can predict - but we can't know that a program - an arbitrary program - will halt. Evolution is much the same, but most people are worse at it because they make the mistake of prioritizing human-values as evolutionary advantages for all species. For example, cows get slaughtered by the billion by humans. But they're an evolutionary success story from a Darwinian perspective: by being easy to domesticate by early tribes and delicious, they've proliferated far beyond anything which would've happened un-aided by humans.
- dllthomas 13y ago
  For any arbitrary program, we may be able to know that it will halt.
  - HCIdivision17 13y ago
    For any very simple arbitrary program, perhaps. But certainly not in general. That's sort of the point of the Halting Problem: you can't know because it is undecidable. Of course, there are simple and trivial programs that can be specifically analyzed, but we're definitely not to that level on any of the stuff under discussion here. The analogy really is pretty apt.
    - dllthomas 13y ago
      The halting problem is undecidable much like logic is incomplete. There will always be true statements we can't prove, and there will always be programs that might or might not halt. That doesn't mean that we can't prove lots of interesting things, it just means we can't promise to prove it when handed a program. We can try, and sometimes we'll succeed.
      - XorNot 13y ago
        The thing is a very simple program can be argued to be have been executed by the person's reading it. You know it halts because you look at the code, step through it mentally and - hey, it halts. But that's the nature of the problem: you know it halts because just executed it till it halts.
        dllthomas 13y ago
        Yes, running them until they halt is one way of determining that a program halts on a given input. However, we can prove things do or don't halt without that. Consider running, on an idealized machine (so no overflows), while(i>0) { i * 2; } I think you would agree that this clearly never halts for any i > 0, and I think it also clear that we did not determine that by running it until it did not halt (because there is no such point). Turing proved that for some programs there is nothing we can do but run them and see. That doesn't mean that's all we can ever do.

by rflrob 13y ago

XorNot 13y ago

You contradict your own point though: yes, we can predict - but we can't know that a program - an arbitrary program - will halt. Evolution is much the same, but most people are worse at it because they make the mistake of prioritizing human-values as evolutionary advantages for all species. For example, cows get slaughtered by the billion by humans. But they're an evolutionary success story from a Darwinian perspective: by being easy to domesticate by early tribes and delicious, they've proliferated far beyond anything which would've happened un-aided by humans.

dllthomas 13y ago
For any arbitrary program, we may be able to know that it will halt.
- HCIdivision17 13y ago
  For any very simple arbitrary program, perhaps. But certainly not in general. That's sort of the point of the Halting Problem: you can't know because it is undecidable. Of course, there are simple and trivial programs that can be specifically analyzed, but we're definitely not to that level on any of the stuff under discussion here. The analogy really is pretty apt.
  - dllthomas 13y ago
    The halting problem is undecidable much like logic is incomplete. There will always be true statements we can't prove, and there will always be programs that might or might not halt. That doesn't mean that we can't prove lots of interesting things, it just means we can't promise to prove it when handed a program. We can try, and sometimes we'll succeed.
    - XorNot 13y ago
      The thing is a very simple program can be argued to be have been executed by the person's reading it. You know it halts because you look at the code, step through it mentally and - hey, it halts. But that's the nature of the problem: you know it halts because just executed it till it halts.
      - dllthomas 13y ago
        Yes, running them until they halt is one way of determining that a program halts on a given input. However, we can prove things do or don't halt without that. Consider running, on an idealized machine (so no overflows), while(i>0) { i * 2; } I think you would agree that this clearly never halts for any i > 0, and I think it also clear that we did not determine that by running it until it did not halt (because there is no such point). Turing proved that for some programs there is nothing we can do but run them and see. That doesn't mean that's all we can ever do.