If it’s not fast enough, it doesn’t matter how good it is
Sure! My brute-force bitwise algorithm generator won’t be fast enough to generate any algorithm of length 300 bits, and our universe probably can’t support any representation of any algorithm of length greater than (the number of atoms in the observable universe) ~ 10^82 bits. (I don’t know much about physics, so this could be very wrong, but think of it as a useful bound. If there’s a better one (e.g. number of Planck volumes in the observable universe), substitute that and carry on, and also please let me know!)
Part of the issue with this might be programs that don’t work or do anything (Beyond the trivial, it’s not clear how to select for this, outside of something like AlphaGo.)
Another class of algorithms that cause problems are those that don’t do anything useful for some number of computations, after which they begin to output something useful. We don’t really get to know if they will halt, so if the useful structure emerges after some number of steps, we may not be committed to or able to run it that long.
I’m not a physicist either, but quantum mechanics might change the limits. (If it scales, though this might leave input and output limits; if the quantum computer can’t store the output in classical mode, then it’s ability to run the program probably doesn’t matter. This might make less efficient crypto systems more secure, by virtue of size.*)
Sure! My brute-force bitwise algorithm generator won’t be fast enough to generate any algorithm of length 300 bits, and our universe probably can’t support any representation of any algorithm of length greater than (the number of atoms in the observable universe) ~ 10^82 bits. (I don’t know much about physics, so this could be very wrong, but think of it as a useful bound. If there’s a better one (e.g. number of Planck volumes in the observable universe), substitute that and carry on, and also please let me know!)
Another class of algorithms that cause problems are those that don’t do anything useful for some number of computations, after which they begin to output something useful. We don’t really get to know if they will halt, so if the useful structure emerges after some number of steps, we may not be committed to or able to run it that long.
I’m not a physicist either, but quantum mechanics might change the limits. (If it scales, though this might leave input and output limits; if the quantum computer can’t store the output in classical mode, then it’s ability to run the program probably doesn’t matter. This might make less efficient crypto systems more secure, by virtue of size.*)
*Want your messages to be more secure? Padding.
Want your key more secure? Length.