[Numpy-discussion] Quick Question about Optimization

Hoyt Koepke hoytak@gmail....
Mon May 19 15:04:46 CDT 2008


On Mon, May 19, 2008 at 12:53 PM, Robin <robince@gmail.com> wrote:
> Hi,
>
> I think my understanding is somehow incomplete... It's not clear to me
> why (simplified case)
>
> a[curidx,:] = scalar * a[2-curidx,:]
> should be faster than
> a = scalar * b
>
> In both cases I thought the scalar multiplication results in a new
> array (new memory allocated) and then the difference between copying
> that result into the existing array u[curix,:] or reassining the
> reference u to that result should be very similar?
>
> If anything I would have thought the direct assignment would be
> quicker since then there is no copying.
>
> What am I missing?

Actually, I think you are correct.  My bad.  I was mainly thinking in
terms of weave.blitz, where it would make a difference, then
translating back...

--Hoyt

+++++++++++++++++++++++++++++++++++
Hoyt Koepke
UBC Department of Computer Science
http://www.cs.ubc.ca/~hoytak/
hoytak@gmail.com
+++++++++++++++++++++++++++++++++++


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