#962: GEOSNode is much slower that GEOSUnaryUnion
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Reporter: komzpa | Owner: geos-devel@…
Type: defect | Status: new
Priority: major | Milestone:
Component: Default | Version: 3.6.2
Severity: Unassigned | Resolution:
Keywords: |
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Comment (by mdavis):
The data in #982 is absolutely a worst-case scenario for CascadedUnion,
since it has very little spatial coherence, and the number of nodes is on
the order of O(n^2). So it's not surprising it's very slow.
Invoking CascadedUnion only on union exception would be a quick fix for
this case. But I have my doubts about using Cascaded Union at all for
sets of lines. I think it should be possible to determine how the
Cascaded Union code is improving robustness (likely due to snapping) and
simply invoke that directly. Although, the snapping heuristic is possibly
low-performance itself, and so it might not produce much advantage.
Ultimately, better noding is going to be the solution. Either snap-
rounding, or perhaps with further research an approach that preserves more
precision where possible.
--
Ticket URL: <https://trac.osgeo.org/geos/ticket/962#comment:6>
GEOS <http://trac.osgeo.org/geos>
GEOS (Geometry Engine - Open Source) is a C++ port of the Java Topology Suite
(JTS).
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