[RQt-devel] performance of Qt's bsp tree

[Yihui Xie]

Sounds great. Thanks! It seems it's still difficult to get around the
memory issue: it is almost impossible to index 1 million points on my
laptop (R will not respond for several minutes if I try to brush the
points).

Regards,
Yihui
--
Yihui Xie <xieyihui at gmail.com>
Phone: 515-294-2465 Web: http://yihui.name
Department of Statistics, Iowa State University
2215 Snedecor Hall, Ames, IA



On Fri, Apr 8, 2011 at 7:47 AM, Michael Lawrence
<lawrence.michael at gene.com> wrote:
> Just a follow-up to some some concerns from the cranvas group about the poor
> performance of the BSP indexing of QGraphicsScene. It looks like the index
> was pretty much rewritten between Qt 4.5 (what I showed at DSC 09) and Qt
> 4.6. In fact, it was being rewritten during the DSC. This has resulted in
> apparently much poorer performance. It now takes 4-5 seconds to index only
> 100,000 points. Don't even think about indexing a million.
>
> Whatever they changed, it's now really slow to add a point one at a time to
> the index. I think they might be sorting something each time. They're using
> quick sort, but a binary tree would be a better idea for efficient updating.
> Thus, I changed qtpaint to disable the index while populating the scene and
> then re-enable the index after all objects have been added. This is
> considerably faster. Now 100,000 points take 0.2 seconds and a million takes
> 2 seconds. Nice and linear. Not as fast as before though, because there is
> still a sort.
>
> Michael
>
>
>
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