[Boost-bugs] [Boost C++ Libraries] #11242: Accuray issue with geometry::difference() in version Boost 1.57 (and 1.58)

Subject: [Boost-bugs] [Boost C++ Libraries] #11242: Accuray issue with geometry::difference() in version Boost 1.57 (and 1.58)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-04-25 12:11:53

#11242: Accuray issue with geometry::difference() in version Boost 1.57 (and 1.58)
-------------------------------+---------------------------
 Reporter:  mikkel.stegmann@…  |      Owner:  barendgehrels
     Type:  Bugs               |     Status:  new
Milestone:  To Be Determined   |  Component:  geometry
  Version:  Boost 1.57.0       |   Severity:  Problem
 Keywords:                     |
-------------------------------+---------------------------
 I'm having an accuracy issue with geometry::difference() in Boost v1.57
 (and v1.58) that I didn't see with v1.55. The test program is listed
 below. I compiled using g++ 4.4.7 on Ubuntu 12.04.

 Result using Boost v1.55:

 {{{
          249.232           761.09
          249.232           760.98
           265.89           760.98
           265.89          729.219
           94.021          729.219
           94.021           761.09
          249.232           761.09
 }}}

 Result using Boost v1.57 (and v1.58):

 {{{
 249.232003466816           761.09
          249.232           760.98
           265.89 760.979984987659
           265.89          729.219
           94.021          729.219
           94.021           761.09
 249.232003466816           761.09
 }}}

 Apparently, it is related to the rescaling policy introduced in v1.56. I
 can mitigate the issue by defining the BOOST_GEOMETRY_NO_ROBUSTNESS.

 Best regards,

 Mikkel B. Stegmann

 ----

 {{{
 #include <boost/foreach.hpp>
 #include <boost/geometry/geometries/point_xy.hpp>
 #include <boost/geometry.hpp>

 #include <cstdio>
 #include <assert.h>

 int main() {

   // 2D point with double precision
   typedef boost::geometry::model::d2::point_xy<double> BoostPoint;

   // 2D polygon, ring type: clockwise, closed ("the first point must be
 spatially equal to the last point")
   typedef boost::geometry::model::polygon<BoostPoint> BoostPolygon;

   BoostPolygon rectangleA;
   rectangleA.outer().push_back(BoostPoint( 94.021, 729.219)); // clock-
 wise points
   rectangleA.outer().push_back(BoostPoint( 94.021, 761.090));
   rectangleA.outer().push_back(BoostPoint(265.890, 761.090));
   rectangleA.outer().push_back(BoostPoint(265.890, 729.219));
   rectangleA.outer().push_back(BoostPoint( 94.021, 729.219)); // close

   BoostPolygon rectangleB;
   rectangleB.outer().push_back(BoostPoint(249.232, 760.980)); // clock-
 wise points
   rectangleB.outer().push_back(BoostPoint(249.232, 780.980));
   rectangleB.outer().push_back(BoostPoint(319.232, 780.980));
   rectangleB.outer().push_back(BoostPoint(319.232, 760.980));
   rectangleB.outer().push_back(BoostPoint(249.232, 760.980)); // close

   std::list<BoostPolygon> differencePolygons;
   boost::geometry::difference(rectangleA, rectangleB, differencePolygons);
   assert(differencePolygons.size()==1);

   BOOST_FOREACH(const BoostPoint &point,
 differencePolygons.front().outer()) {
     printf("%16.15g %16.15g\n", point.x(), point.y());
   }

   return 0;
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11242>
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