On Thu, Jun 4, 2015 at 8:57 AM, Stefan Karpinski <[email protected]> wrote: > Are you asking about the task approach or the manual iteration approach? > Manual iteration, yes (otherwise all iteration would be slow); tasks, I'm > not sure how inlining would be possible.
Sorry I was trying to come up with a short description of what I am thinking of (but apparently failed). I was talking about a "wrapper" approach. i.e. wrap the iterator state in a type and define a "indexless" iterator on the wrapper type. This is what I meant by "fast" and but relying on type stablity of the original type. If the wrapper type is parametrized, it would probably be as fast as manual iteration, but it will error out if the underlaying iter methods is not type stable. If the wrapper type is not parametrized, there will probably be a lot of boxing/unboxing and runtime dispatch since typeinf cannot infer the type of the field (which store the iteration index etc) So by "inlining the type" I mean sth like ``` type A a end @inline get(a::A) = a.a @inline set(a::A, b) = (a.a = b) function f1(c) a = A() set(a, c) get(a) end function f2(c) a = c a end ``` Can `f1` be made as fast as `f2` by realising `A` is not leaked anywhere outside the function and can be treated as a bundle of local variables? > > On Thu, Jun 4, 2015 at 8:52 AM, Yichao Yu <[email protected]> wrote: >> >> On Wed, Jun 3, 2015 at 3:16 PM, Stefan Karpinski >> <[email protected]> wrote: >> > You could use a task, but the performance would be much less good than >> > explicitly manipulating the iteration state for many things. >> > >> >> Manually iterating is not that bad so I think I would prefer a >> solution that yield similar performance. >> >> Actually, can(/is it reasonable to make) type inference inline the >> type as well if all use of it are inlined? >> >> > >> >> On Jun 2, 2015, at 6:45 PM, Yichao Yu <[email protected]> wrote: >> >> >> >> I'm wondering what is the best way to do the equivalant with the >> >> following in python. >> >> >> >> ``` >> >> In [1]: a = range(20) >> >> >> >> In [2]: it = iter(a) >> >> >> >> In [3]: for i in it: >> >> if i == 10: >> >> break >> >> ...: >> >> >> >> In [4]: for i in it: >> >> ...: print(i) >> >> ...: >> >> 11 >> >> 12 >> >> 13 >> >> 14 >> >> 15 >> >> 16 >> >> 17 >> >> 18 >> >> 19 >> >> ``` >> >> >> >> I know that I can call `start`, `next` and `done` manually but it >> >> would be nice if I can avoid that. >> >> >> >> I could also wrap the returned value of next in a type but I don't >> >> know how to make it both generic and fast, e.g. I want the typeinf to >> >> infer the type as easy as if I call the `start`.... methods manually >> >> and I don't want to rely on `next` being type stable (and AFAICT, the >> >> `next` for Any array is not). >> >> >> >> >> >> The exact format doesn't have to be the same with the python version >> >> but I do want to use `for` loop instead of `while`. > >
