Changes between Initial Version and Version 14 of Ticket #22455


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Timestamp:
Aug 22, 2017, 2:51:04 PM (5 years ago)
Author:
Jean-Philippe Labbé
Comment:

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  • Ticket #22455

    • Property Status changed from new to needs_work
    • Property Authors changed from to Christoph Pegel
    • Property Cc Jean-Philippe Labbé Moritz Firsching Vincent Delecroix added
    • Property Branch changed from to u/jipilab/22455
    • Property Commit changed from to 3eb371114a9420b544afec58074dc81cbc78a3ea
    • Property Keywords days88 added
    • Property Reviewers changed from to Jean-Philippe Labbé
  • Ticket #22455 – Description

    initial v14  
    1 The method `_facet_adjacency_matrix` of the `Polyhedron` class produces a wrong matrix for polyhedra that are not of same dimension as their ambient space. For example, a triangle sitting in `ZZ^3` results in the adjacency matrix
     1The method `_facet_adjacency_matrix` of the `Polyhedron` class produces a wrong matrix for polyhedra that are not of same dimension as their ambient space. For example,
    22
    33{{{
     4sage: s = polytopes.simplex(2)
     5sage: s._facet_adjacency_matrix()
     6
    47[0 1 1 1]
    58[1 0 0 0]
     
    811}}}
    912
     13while it should return
     14
     15{{{
     16sage: s._facet_adjacency_matrix()
     17[0 1 1]
     18[1 0 1]
     19[1 1 0]
     20}}}
     21
    1022The problem is that what is being checked is the ambient H-representation of some face being of length 2, which is interpreted as "2 facets are intersecting". This approach doesn't work for codimension not equal to 0.
    1123