Opened 5 years ago
Closed 4 years ago
#23355 closed defect (fixed)
affine hull of one point polyhedron
Reported by:  moritz  Owned by:  

Priority:  minor  Milestone:  sage8.0 
Component:  geometry  Keywords:  polyhedron 
Cc:  vdelecroix, jipilab  Merged in:  
Authors:  Moritz Firsching  Reviewers:  JeanPhilippe Labbé 
Report Upstream:  N/A  Work issues:  
Branch:  9fccf4e (Commits, GitHub, GitLab)  Commit:  9fccf4ed8fd21d8500ad78cbcfac142847cffccd 
Dependencies:  #22804  Stopgaps: 
Description
When using the orthogonal/orthonormal feature of the affine hull function of a polyhedron (introduced in #22804), there is a problem with the one point polyhedron:
sage: P = Polyhedron([[7]]) sage: P A 0dimensional polyhedron in ZZ^1 defined as the convex hull of 1 vertex sage: P.affine_hull() A 0dimensional polyhedron in ZZ^0 defined as the convex hull of 1 verte sage: P.affine_hull(orthogonal='True')  TypeError Traceback (most recent call last) ... TypeError: unsupported operand parent(s) for *: 'Full MatrixSpace of 0 by 0 dense matrices over Integer Ring' and 'Ambient free module of rank 1 over the principal ideal domain Integer Ring' sage: P.affine_hull(orthonormal='True')  TypeError Traceback (most recent call last) ... TypeError: unsupported operand parent(s) for *: 'Full MatrixSpace of 0 by 0 dense matrices over Integer Ring' and 'Ambient free module of rank 1 over the principal ideal domain Integer Ring'
This is how it should be:
sage: P = Polyhedron([[7]]); P A 0dimensional polyhedron in ZZ^1 defined as the convex hull of 1 vertex sage: P.affine_hull() A 0dimensional polyhedron in ZZ^0 defined as the convex hull of 1 vertex sage: P.affine_hull(orthonormal='True') A 0dimensional polyhedron in QQ^0 defined as the convex hull of 1 vertex sage: P.affine_hull(orthogonal='True') A 0dimensional polyhedron in QQ^0 defined as the convex hull of 1 vertex
Change History (7)
comment:1 Changed 5 years ago by
 Branch set to u/moritz/fix_one_point_affine_hull
comment:2 Changed 5 years ago by
 Cc vdelecroix added
 Commit set to 08d951f6f1cffa278948a7913360c3999407670a
 Status changed from new to needs_review
comment:3 Changed 5 years ago by
Hi Moritz,
Could you add a reference to this ticket just before the tests you added?
Apart from that it looks good to me! You can set it to positive review on my behalf once this is done!
comment:4 Changed 5 years ago by
 Cc jipilab added
 Reviewers set to JeanPhilippe Labbé
comment:5 Changed 5 years ago by
 Commit changed from 08d951f6f1cffa278948a7913360c3999407670a to 9fccf4ed8fd21d8500ad78cbcfac142847cffccd
Branch pushed to git repo; I updated commit sha1. New commits:
9fccf4e  added trac number in test

comment:6 Changed 5 years ago by
 Status changed from needs_review to positive_review
thanks for the review, JP!
I added the desired reference and will put it on 'positive review' as you suggested
comment:7 Changed 4 years ago by
 Branch changed from u/moritz/fix_one_point_affine_hull to 9fccf4ed8fd21d8500ad78cbcfac142847cffccd
 Resolution set to fixed
 Status changed from positive_review to closed
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The reason why this didn't work properly is the fact that if a Matrix is generated from a list it cannot correctly guess its dimensions if the list is empty. The whole fix is simply to exchange the line
by
giving the dimensions explicitly. I also added a doctest (under the section TESTS) documenting that the bug is fixed.
New commits:
prescribe size of matrix explicitely
added hidden doctest