[Numpy-discussion] Arithmetic on arrays of pointers

Dan Goodman dg.gmane@thesamovar....
Tue Apr 28 21:05:20 CDT 2009


Hi all,

I have a slightly strange idea for something I would like to do with 
numpy which I guess probably doesn't exist, but I may be wrong. What I 
want to do, essentially, is to have two arrays of equal size, say X and 
Y, of pointers to doubles say. Then I want to do (in C notation) *x += 
*y for each x, y in X, Y. I'd like to write this in Python as X+=Y where 
X and Y understand that they consist of arrays of pointers to doubles 
and that it should do the arithmetic on the values pointed to. Now I can 
do this in C easily enough, and integrate it with numpy via weave or 
whatever (it only took a few lines using scipy.weave.inline), but it 
would be really nice if something along these lines were already in 
numpy or an extension of it already. Anyone know of anything like that 
or had any experience with similar situations?

I'd also like to be able to take pointers and do pointer arithmetic too 
(because I want to construct the 1D arrays X, Y above from values picked 
from a variety of possible data structures, including dense and sparse 
2D arrays, but in such a way that the code that uses these values 
doesn't have to know where the values came from in these data 
structures). Why? you might ask. Well, because I'm writing simulation 
code which involves scheduling events in the future (simple events like 
add a value to another value), but the library is supposed to be easily 
extensible for people who don't know C so I want to make it as easy to 
use as possible.

Well, that's a slightly underdefined problem, basically I just have a 
vague idea that something like the above would be useful to me and I'm 
looking for any ideas that might seem relevant.

Thanks in advance!
Dan



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