[Cython] some pull requests for 0.16?

mark florisson markflorisson88 at gmail.com
Thu Mar 22 15:21:43 CET 2012

On 21 March 2012 20:24, Robert Bradshaw <robertwb at gmail.com> wrote:
> On Wed, Mar 21, 2012 at 6:47 AM, mark florisson
> <markflorisson88 at gmail.com> wrote:
>> On 20 March 2012 18:51, Stefan Behnel <stefan_ml at behnel.de> wrote:
>>> mark florisson, 20.03.2012 17:40:
>>>> On 18 March 2012 11:58, Stefan Behnel wrote:
>>>>> I put up two new pull requests on github:
>>>>> Implementation of PEP 380 (yield from):
>>>>> https://github.com/cython/cython/pull/96
>>>>> Rewrite of dict iteration:
>>>>> https://github.com/cython/cython/pull/95
>>>>> Given that the release of 0.16 has currently slowed down a bit, and given
>>>>> that these are really nice features, could someone (and especially Mark, as
>>>>> the responsible release manager) take a look at them and give an opinion
>>>>> regarding their suitability for 0.16?
>>>> Sorry about the slowdown, my BT internet connection at home got closed
>>>> off, so working on a release is rather hard, hopefully that will be
>>>> fixed within the next few days.
> Thanks for the status update. Is there a separate release branch, or
> are you working off the github master? Is there a list of
> issues/blockers somewhere?

I created a release branch called release0.16 (there was a previous
release branch for 0.15.1 which I could have pruned as well).

>>>> Anyway, during the sprints Dag worked
>>>> on the numpy attributes accesses to generate non-deprecated numpy
>>>> code, I'm not sure how far along that is and if we can get that in as
>>>> well, or have it wait until 0.16.1.
>>> I wouldn't mind if my changes waited for 0.16.1 as well, as long as that's
>>> not too long from now. There will certainly be things to fix after the
>>> release anyway.
>>>> I worked on enhancing fused types runtime dispatching (e.g. select the
>>>> right specialization at runtime from the argument types), especially
>>>> on matching buffers. It's also a bit of a rewrite as the complexity
>>>> grew quite a bit and ndarray and fused types were broken in subtle
>>>> ways (I would do the pull request now if I hadn't left the code at
>>>> home :).
>>> I took a tiny look at that when I wrote a test case and was surprised to
>>> see that it imports "sys" inside of the generated function. Looks like
>>> there's a bit left to optimise.
>>> I faintly remember a blog post (or more than one) by PJ Eby when he wrote a
>>> "generic functions" module. It uses type dispatching as well, and he wrote
>>> about the ways he found to tune that. Might be an interesting read.
>> Thanks, I'll look into that. Maybe the modules could be bound as
>> locals through default arguments.
>>>> Finally, there is a serious bug in the reversed(range()) optimization
>>>> that Mike Graham discovered when working on the range() optimization
>>>> with a runtime step, which is basically wrong for any step that is not
>>>> 1 or -1 (it simply swaps the bounds with an offset by 1, but it
>>>> actually has to figure out what the actual last value was in the range
>>>> and use that as the start instead). I personally consider this a
>>>> blocker, so I'll try contacting Mike and see if he is still
>>>> (interested in) working on that.
>>> Interesting. Yes, I can well imagine that being wrong. These things are
>>> exceedingly tricky.
>>> However, it's easy to disable the optimisation for a specific case - likely
>>> easier than fixing it.
>>> Also, I don't consider this a blocker. It's not like it works in the
>>> current release, so it's not a regression compared to that.
>> Yes, it's not a regression, but I find it hard to release something
>> that is so broken, and I feel it kind of represents a lack of care
>> which may make people believe Cython can't be taken seriously.
> I'm usually in the "not a regression" camp as well, but this is pretty
> fundamental. Sounds like an easy fix, or at least an easy-to-disable
> optimization.
>>>> As for the two pull requests, both are quite large, but the dict
>>>> iteration rewrite is more like an enhancement whereas the 'yield from'
>>>> is really a new (somewhat big) feature. I would personally prefer to
>>>> merge only enhancements and bug fixes, but not new features.
>>> Funny. I would have proposed the opposite, because I consider the "yield
>>> from" implementation (as a new language feature) safer than the dict
>>> iteration (which impacts existing code). As I said, I wouldn't mind
>>> postponing both to 0.16.1, but I think it would be better to get them out
>>> and have people use them, so that we can also fix the bugs earlier.
>> A good point. My reasoning was that we want less new functionality per
>> release, and keeping 'yield from' out of 0.16 makes us push out the
>> next release earlier as we will have pending functionality we want to
>> get out there. If the dict iteration is tested well enough (and it
>> looked to me like that), then hopefully code in sage or lxml will
>> break if there are leftover bugs, or our next beta might catch them
>> (or some). If you do want it in now, then that's fine with me as well,
>> you have a point.
> Has this been pushed into the devel branch for sufficient testing
> there (e.g. on Sage)? Personally, I'd like to see the release get out
> sooner rather than later.
> - Robert
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