Okay cool thanks your input. For any one else has a similar problem - writing a simple iterator function in python (which is a generator) and assigning that to the __iter__ member works well as an alternative. For me this turned out to be considerably faster than using a c++ iterator/getitem iteration.
On 19 January 2012 19:37, Jim Bosch <tallji...@gmail.com> wrote: > On 01/19/2012 02:08 PM, babak wrote: > >> Hi guys, >> >> Has anyone encountered (what feels like) quite slow iteration when looping >> over small containers ? I'm in a situation where I'm iterating over >> 100000+ >> 3d vectors and its taking much longer than I'd expect. The vector type is >> bound via boost::python and has an iter method which uses range(being, >> end) >> for the iteration. >> >> I've attached a simple example binding and python test to illustrate what >> I >> mean more clearly. I'm under the impression that in a situation like this >> the overhead of creating the iterator is greater than the actual >> iteration, >> but thats just a guess. Alternatively my perspective on what the iteration >> speed should be might be completely skewed, so any help in clarifying >> what's >> going on here would be greatly appreciated. >> >> > My sense is that this is something that really can't be expected to be > efficient across the C++/Python boundary. There is some overhead > associated with creating the exposures, and there's also some overhead in > converting the types, especially if those vectors aren't builtin numeric > types. > > If you can redesign the C++/Python boundary to convert your vectors > directly into Python lists or tuples instead of wrapped C++ vectors, I > expect you'll see an improvement, because you'll be able to take advantage > of whatever optimization the Python developers have put into iteration over > those classes. Of course, it's best by far to do whatever iteration you > can in C++ if performance is important, but I'm guessing that's not an > option here. > > Jim > > > ______________________________**_________________ > Cplusplus-sig mailing list > Cplusplus-sig@python.org > http://mail.python.org/**mailman/listinfo/cplusplus-sig<http://mail.python.org/mailman/listinfo/cplusplus-sig> >
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