Given Andrew's original post, that makes sense, although it wasn't clear to me from just reading your response.
Cheers! On Tue, Feb 25, 2014 at 11:17 AM, Stefan Karpinski <ste...@karpinski.org>wrote: > I was talking about fully automatic memoization, which does not play > nicely with the type system. Thus, it's a speedup in a language where every > function is loosely typed anyway, but a distinct slow down in a language > with nice type behavior (and an implementation smart enough to leverage > it). That's why I called automatic memoization "worse than useless" – you > take a possibly slow, but nicely typed function and turn it into poorly > typed, memoized function. There might be a way to make it work better, but > I suspect it would require some very deep language support and would > generally be inferior to just having people use an explicit cache > structure. In the case of npartitions, this is precisely what's happening: > there's an explicit, correctly typed cache. > > > On Tue, Feb 25, 2014 at 1:36 PM, Kevin Squire <kevin.squ...@gmail.com>wrote: > >> What you're suggesting is memoization, which has come up a number of >>> times. The short version is that it is an easy way to speed up a slow >>> language but is worse than useless in fast languages. You don't see people >>> doing memoization in C or Fortran, do you? >>> >> >> That's a little, um, strong, don't you think? Certainly it's not common, >> but probably not "worse than useless". ;-) (The lack of a standard >> map/dictionary/hash table in these languages probably contributes as well.) >> >> A couple of examples in Julia where it's useful (and would be just as >> useful in C or Fortran): >> >> >> https://github.com/JuliaLang/julia/blob/master/base/combinatorics.jl#L304-L321 >> >> https://github.com/JuliaLang/julia/blob/master/base/combinatorics.jl#L368-L379 >> >> (Those should probably be wrapped in let statements. I'll do that.) >> >> These are not common functions, of course, but memoization here is >> definitely useful. >> >> Cheers! >> Kevin >> > >
