On Fri, Feb 28, 2014 at 5:52 AM, Julian Taylor < jtaylor.deb...@googlemail.com> wrote:
> performance should not be impacted as long as we stay on the stack, it > just increases offset of a stack pointer a bit more. > E.g. nditer and einsum use temporary stack arrays of this type for its > initialization: > op_axes_arrays[NPY_MAXARGS][NPY_MAXDIMS]; // both 32 currently > The resulting nditer structure is then in heap space and dependent on > the real amount of arguments it got. > So I'm more worried about running out of stack space, though the limit > is usually 8mb so taking 128kb for a short while should be ok. > > On 28.02.2014 13:32, Francesc Alted wrote: > > Well, what numexpr is using is basically NpyIter_AdvancedNew: > > > > > https://github.com/pydata/numexpr/blob/master/numexpr/interpreter.cpp#L1178 > > > > and nothing else. If NPY_MAXARGS could be increased just for that, and > > without ABI breaking, then fine. If not, we should have to wait until > > 1.9 I am afraid. > > > > On the other hand, increasing the temporary arrays in nditer from 32kb > > to 128kb is a bit worrying, but probably we should do some benchmarks > > and see how much performance would be compromised (if any). > > > > Francesc > > > > On 2/28/14, 1:09 PM, Julian Taylor wrote: > >> hm increasing it for PyArrayMapIterObject would break the public ABI. > >> While nobody should be using this part of the ABI its not appropriate > >> for a bugfix release. > >> Note that as it currently stands in numpy 1.9.dev we will break this ABI > >> for the indexing improvements. > >> > >> Though for nditer and some other functions we could change it if thats > >> enough. > >> It would bump some temporary arrays of nditer from 32kb to 128kb, I > >> think that would still be fine, but getting to the point where we should > >> move them onto the heap. > These sort of changes can have subtle side effects and need lots of testing in a release cycle. Bugfix release cycles are kept short by restricting changes to those that look simple and safe. <snip> Chuck
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