[Boost-bugs] [Boost C++ Libraries] #8434: Sloan Ordering Gives Incorrect Results

Subject: [Boost-bugs] [Boost C++ Libraries] #8434: Sloan Ordering Gives Incorrect Results
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-04-13 12:33:37

#8434: Sloan Ordering Gives Incorrect Results
----------------------------------------------------+-----------------------
 Reporter:  Allen Barnett <allen@…>                 |       Owner:  jewillco
     Type:  Bugs                                    |      Status:  new     
Milestone:  To Be Determined                        |   Component:  graph   
  Version:  Boost 1.53.0                            |    Severity:  Problem 
 Keywords:                                          |  
----------------------------------------------------+-----------------------
 I was trying to use Sloan ordering to reduce the bandwidth on a couple of
 my finite element meshes. It did not give very good results; the bandwidth
 after reordering was exactly equal to number of vertexes! So, I tried the
 example program here:
 http://www.boost.org/doc/libs/1_53_0/libs/graph/example/sloan_ordering.cpp

 I expected the results given in the comments in the example file:
 {{{
 /*
   Sample Output
   #####################################
   ### First light of sloan-ordering ###
   #####################################

   original bandwidth: 8
   original profile: 42
   original max_wavefront: 7
   original aver_wavefront: 4.2
   original rms_wavefront: 4.58258

   Starting vertex: 0
   Pseudoperipheral vertex: 9
   Pseudoperipheral radius: 4

   Sloan ordering starting at: 0
     0 8 3 7 5 2 4 6 1 9
     bandwidth: 4
     profile: 28
     max_wavefront: 4
     aver_wavefront: 2.8
     rms_wavefront: 2.93258

   Sloan ordering without a start-vertex:
     8 0 3 7 5 2 4 6 1 9
     bandwidth: 4
     profile: 27
     max_wavefront: 4
     aver_wavefront: 2.7
     rms_wavefront: 2.84605

   ###############################
   ### sloan-ordering finished ###
   ###############################
 */
 }}}
 Instead I got:
 {{{
 #####################################
 ### First light of sloan-ordering ###
 #####################################

 original bandwidth: 8
 original profile: 58
 original max_wavefront: 7
 original aver_wavefront: 4.2
 original rms_wavefront: 4.58258

 Starting vertex: 0
 Pseudoperipheral vertex: 9
 Pseudoperipheral radius: 4

 Sloan ordering starting at: 0
   0 7 4 9 1 6 2 5 3 8
   bandwidth: 8
   profile: 55
   max_wavefront: 6
   aver_wavefront: 3.6
   rms_wavefront: 3.94968

 Sloan ordering without a start-vertex:
   8 5 4 9 1 7 6 2 0 3
   bandwidth: 9
   profile: 66
   max_wavefront: 7
   aver_wavefront: 4.2
   rms_wavefront: 4.66905

 ###############################
 ### sloan-ordering finished ###
 ###############################
 }}}
 You can see that the current results are in line with what I was
 experiencing with my own meshes, namely, no reduction in bandwidth or
 profile.

 Sloan ordering seems to have first appeared in boost 1.30.0. I tried that
 version too, and it gives essentially the same results as I see with 1.53.
 So, perhaps it's the comments in the example program that need to be
 updated and Sloan ordering is not appropriate for my meshes.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8434>
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