[Boost-bugs] [Boost C++ Libraries] #5954: distance_pythagoras skips sqrt() step

Subject: [Boost-bugs] [Boost C++ Libraries] #5954: distance_pythagoras skips sqrt() step
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-09-28 17:01:21

#5954: distance_pythagoras skips sqrt() step
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 Reporter:  mloskot                                    |       Owner:  barendgehrels
     Type:  Bugs                                       |      Status:  new          
Milestone:  To Be Determined                           |   Component:  geometry     
  Version:  Boost Development Trunk                    |    Severity:  Problem      
 Keywords:  pythagoras,geos,douglas,peucker,algorithm  |  
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 A problem with
 [http://lists.osgeo.org/pipermail/ggl/2011-September/001533.html Polygon
 Douglas–Peucker simplification] results have been reported.

 There seems to be a bug in calculation of distance using Pythagoras
 Theorem. The problem is that the distance calculation is somehow omitting
 call to sqrt() leading to incomplete results.

 It may be a problem with dispatching and execution execution paths in
 distance_pythagoras.hpp, so this part needs to be thoroughly reviewed.

 Meanwhile, the patch attached provides a quick fix. The fix solves the
 reported problem, so the Boost.Geometry generates expected results. Also,
 the posted test case has been checked using GEOS and the patched
 distance_pythagoras generates results consistent with those obtained from
 GEOS. Means, the fix seems to be correct.

 But, it causes number of unit test failures, so I decided to not to commit
 it this fix.

 Barend, please get in touch when you will have a moment.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5954>
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