[Numpy-discussion] (cumsum, broadcast) in (numexpr, weave)

srean srean.list@gmail....
Tue Jun 21 14:50:38 CDT 2011


Apologies, intended to send this to the scipy list.

On Tue, Jun 21, 2011 at 2:35 PM, srean <srean.list@gmail.com> wrote:
> Hi All,
>
>  is there a fast way to do cumsum with numexpr ? I could not find it,
> but the functions available in numexpr does not seem to be
> exhaustively documented, so it is possible that I missed it. Do not
> know if 'sum' takes special arguments that can be used.
>
> To try another track, does numexpr operators have something like the
> 'out' parameter for ufuncs ? If it is so, one could perhaps use
> add( a[0:-1], a[1,:], out = a[1,:) provided it is possible to preserve
> the sequential semantics.
>
> Another option is to use weave which does have cumsum. However my code
> requires  expressions which implement broadcast. That leads to my next
> question, does repeat or concat return a copy or a view. If they avoid
> copying, I could perhaps use repeat to simulate efficient
> broadcasting. Or will it make a copy of that array anyway ?. I would
> ideally like to use numexpr because I make heavy use of transcendental
> functions and was hoping to exploit the VML library.
>
> Thanks for the help
>
> -- srean
>


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