That's kind of what I was worried about...
I'm working with rTIN's which start as a Delaunay Triangulation, which JTS
helped marvelously for, but once the grid is triangulated, I'm just using
the QuadEdge functions to do what I may with the "grid".
Everything works great if that's all we look at, but the problem is that
this becomes marvelously slow as the grid increases in size. My current
problem with concurrent modification is that the grid is not a viable
triangulation while the deletions of points and lines are taking place (as
soon as the operation completes, everything is dandy). This is only a
problem in the small area around the point that is being worked on, but the
LastFoundQuadEdge locator gets caught up if I try to locate some other quad
on the other side of the grid. My next idea is that maybe more than one
locator could help me out as long as I stay away from locating anywhere
that is currently being worked on.
I'll check out some of the stuff you talked about, thanks Martin.
On Tue, Aug 6, 2013 at 1:44 PM, Martin Davis <[email protected]> wrote:
> AFAIK concurrent algorithms involving triangulations is still an active
> research area. So there is nothing currently in the JTS code which
> explicitly supports this. In particular, you are correct in observing that
> the QuadEdgeSubdivision does not support concurrent modification. This is
> a hard problem, in general.
>
> You might provide a bit more information about the problem you are
> actually trying to solve using a parallel solution. Is it Delaunay
> Triangulation, or some variant of that? If so, you might try doing a
> search for parallel Delaunay algorithms. Agarwhal and Isenburg have some
> some interesting work in this area (focussed on massive datasets rather
> than performance, however).
>
>
>
> On Tue, Aug 6, 2013 at 10:46 AM, Blake Peno <[email protected]>wrote:
>
>> Hey everyone.
>>
>> I'm getting kinda stuck again, and don't really know how to progress. I'm
>> attempting to speed up an algorithm I'm working on that is using QuadEdges
>> to represent data, but I can't seem to find a working way to accomplish
>> this.
>>
>> I've tried concurrently accessing the subdivision for deletions and
>> whatnot, but due to the way the LastFoundQuadEdgeLocator works, this isn't
>> really working (NPEs, etc). My second approach was to split my original set
>> of data into subsets and then merge the subdivisions back together at the
>> end, but this seems to be a disgusting amount of work that won't actually
>> speed anything up. Maybe I'm just going about it the wrong way though.
>>
>> Does anyone have any idea how I could parallelize something like this, or
>> at least concurrently access it? I've spent a few too many days getting
>> nothing done, so I figured I'd ask you guys who actually know what you are
>> doing.
>>
>> Thanks.
>>
>>
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