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Subject: [geometry] Bug again in boost::geometry::union_
From: yohann.benedic_at_[hidden]
Date: 2014-01-30 11:56:36

Hi again,

Still working on some stuff with boost::geometry and stumbled upon another bug-like behavior.
Roughly, build two polygons (one outer ring each) check that they intersect, try to union them and end up with nothing (well, checking that they intersect beforehand is not even relevant).

Sample code is below

void test()
  typedef boost::geometry::model::d2::point_xy<double> boostPoint;
  typedef boost::geometry::model::polygon< boostPoint > boostPolygon;
  typedef boost::geometry::model::multi_polygon< boostPolygon > boostPolygons;
  typedef boostPolygon::ring_type boostRing;

  // both polygons have very close to zero values because they are actually the result of some previous work
  // the bug disappears if I round them down to zero, or if I shift everything by 10000 (doesn't work with a +1 shift though).
  boostPolygon p1;
  boost::geometry::append(p1, boostPoint(7,4));
  boost::geometry::append(p1, boostPoint(7,0));
  boost::geometry::append(p1, boostPoint(5,2));
  boost::geometry::append(p1, boostPoint(3,8.5725275940314722e-16));
  boost::geometry::append(p1, boostPoint(-7,8.8817841970012523e-16));
  boost::geometry::append(p1, boostPoint(-7,10));
  boost::geometry::append(p1, boostPoint(0,17));
  boost::geometry::append(p1, boostPoint(4.2862637970157361e-16,17));
  boost::geometry::append(p1, boostPoint(10,17));
  boost::geometry::append(p1, boostPoint(10,7));

  boostPolygon p2;
  boost::geometry::append(p2, boostPoint(10,17));
  boost::geometry::append(p2, boostPoint(17,10));
  boost::geometry::append(p2, boostPoint(7,10));
  boost::geometry::append(p2, boostPoint(4.2862637970157361e-16,17));


  boostPolygons p_union;

  assert(1,p_union.size()); // this one fails, p_union is empty


I am using boost 1.54 and vertices xs and yx are extracted from the debugger. I guess using different compiler options might fix this issue. Unlike the bug with equals, I was not able to track the problem down in boost code. Again, I haven't seem anything in the 1.55 changelog that indicates it is already fixed.

How safe is boost::geometry for use in prod. code ? Anyone knws of a big project that relies on it ?

Thanks for your time.
[Description :]
Yohann Bénédic
Wireless Engineering and Propagation
Research Engineer
tel. +33 384 544 338


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