[Boost-bugs] [Boost C++ Libraries] #2800: Bug in transposed_structure

Subject: [Boost-bugs] [Boost C++ Libraries] #2800: Bug in transposed_structure
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-02-25 20:01:50

#2800: Bug in transposed_structure
-----------------------------------------------------------------------------------------------------+
 Reporter:  Tiago Requeijo                                                                           |       Owner:  guwi17 
     Type:  Bugs                                                                                     |      Status:  new    
Milestone:  Boost 1.39.0                                                                             |   Component:  uBLAS  
  Version:  Boost 1.38.0                                                                             |    Severity:  Problem
 Keywords:  uBlas, storage scheme, row_major, column_major, triangular_matrix, transposed_structure  |  
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 The transposed_structure template simply takes an upper triangular matrix
 and regards it as the transpose of a lower triangular matrix. It doesn't
 take into account the row/column major storage, leading to the following
 bug:

 If we take the upper matrix U

 1 2 3
 - 4 5
 - - 6

 and regard it as the transpose of a lower matrix L

 1
 2 4
 3 5 6

 without a row/column major swap, then storing the row major version of the
 lower matrix is the same as storing the column major version of the upper
 matrix:

 a) row_major for U: 1 2 3 4 5 6
 b) row_major for L: 1 2 4 3 5 6

 Since the transposed_structure template simply maps the elements to the
 transpose and doesn't change the storage, we are in fact storing b)
 instead of a).

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/2800>
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