On Sun, Jun 14, 2015 at 5:12 PM, Chris Bennight <[email protected]> wrote: > > > I also went ahead and rendered a graphic of what they look like > > Excellent! In fact, this immediately reveals its value, because I see now > that the query polygon is a random star polygon with significant > concavity. Definitely better than a regular convex polygon! 8^) > > Re: Synthetic vs. natural > Completely reasonable. Probably using variable simplified coastlines > would be a good real world case analogue (with a randomly generated query > geometry - asking the question "what countries does this query window > overlap). >
Um, maybe. All depends on use case. There's a pretty much infinite number of scenarios. Here's some (invented) others: - What US census blocks intersect some (larger / smaller) query area? - What ship/truck tracks intersect some area of interest? > > > Re: highly data-dependent > That makes sense - what I"m hopefully trying to come up with are a set of > heuristics that I can use to determine which strategy to use (with the > caveat that I may have to collect stats/profile a data set, and it's not > going to necessarily be correct for every comparison - just hoping to > answer the "best default setting") > In absence of *any* knowledge of the characteristics of query and target, I think the heuristic is "use PreparedGeometry". Maybe there's a refinement to use raw Geometry if the query polygon is low vertex count, or if the target set size is small. And if you find a systemic performance issue with very large query PGs, that's definitely of interest. > > Re: Increasing vertex count by densifying > I think taken in reverse this might be a good analogue for expected > simplification gains? (Granted the is also a decreasing amount of > irregularity in a real simplification, but unless intersects optimizes for > co-linear points I expect the cost is the same). > Lower vertex count is always good 8^) Intersects does not optimize for collinear points. In fact, using monotone chains actually penalizes collinear vertices. (An interesting question is whether adding a maximum run length to MonotoneChain construction would improve performance. But this seems to me like a highly atypical case).
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