Timothy Hochberg wrote: > > > On 1/11/07, *Christopher Barker* <[EMAIL PROTECTED] > <mailto:[EMAIL PROTECTED]>> wrote: > > [CHOP] > > > I'd still like to know if anyone knows how to efficiently loop through > all the elements of a non-contiguous array in C. > > > First, it's not that important if the array is contiguous for this > sort of thing. What you really care about is whether it's > simply-strided (or maybe single-strided would be a better term). > Anyway, the last dimension of the array can be strided without making > things more difficult. All you need to be able to do is to address the > elements of the array as thedata[offset + stride*index]. I don't understand why we need to do thedata[offset + stride * index] instead of thedata[index] when the data are aligned ? It looks like I seriously misunderstood the meaning of alignement...
David > > That being said, the strategy that the ufuncs use, and possibly other > functions as well, is to have the core functions operate only on > simply-strided chunks of data. At a higher level, there is some magic > that parcels up non-contiguous array into simply-strided chunks and > feeds them to core functions. How efficient this is obviously depends > on how large the chunks that the magic parceler manages to extract > are, but typically it seems to work pretty well. > > I don't know whether the magic that does the parcelling is available > for use by random functions or whether it's specific to the ufunc > machinery, I never delved into that end of the ufuncs. > > -tim > > ------------------------------------------------------------------------ > > _______________________________________________ > Numpy-discussion mailing list > Numpy-discussion@scipy.org > http://projects.scipy.org/mailman/listinfo/numpy-discussion _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
