On Thu, Feb 28, 2013 at 7:13 AM, Sebastian Berg <sebast...@sipsolutions.net> wrote: > Hey, > > Maybe someone here already saw it (I don't have a track account, or I > would just create a ticket), but it would be nice if Cython was more > forgiving about contiguous requirements on strides. In the future this > would make it easier for numpy to go forward with changing the > contiguous flags to be more reasonable for its purpose, and second also > to allow old (and maybe for the moment remaining) corner cases in numpy > to slip past (as well as possibly the same for other programs...). An > example is (see also https://github.com/numpy/numpy/issues/2956 and the > PR linked there for more details): > > def add_one(array): > cdef double[::1] a = array > a[0] += 1. > return array > > giving: > >>>> add_one(np.ascontiguousarray(np.arange(10.)[::100])) > ValueError: Buffer and memoryview are not contiguous in the same > dimension. > > This could easily be changed if MemoryViews check the strides as "can be > interpreted as contiguous". That means that if shape[i] == 1, then > strides[i] are arbitrary (you can just change them if you like). This is > also the case for 0-sized arrays, which are arguably always contiguous, > no matter their strides are!
I was under the impression that the primary value for contiguous is that it a foo[::1] can be interpreted as a foo*. Letting strides be arbitrary completely breaks this, right? > PS: A similar thing exists with np.ndarray[...] interface if the user > accesses array.strides. They get the arrays strides not the buffers. > This is not quite related, but if it would be easy to use the buffer's > strides in that case, it may make it easier if we want to change the > flags in numpy in the long term, since one could clean up strides for > forced contiguous buffer requests. > > _______________________________________________ > cython-devel mailing list > cython-devel@python.org > http://mail.python.org/mailman/listinfo/cython-devel _______________________________________________ cython-devel mailing list cython-devel@python.org http://mail.python.org/mailman/listinfo/cython-devel
