#23376 closed defect (fixed)
Equality testing of genera of quadratic forms over ZZ changes the genus and produces false results
Reported by:  sbrandhorst  Owned by:  

Priority:  major  Milestone:  sage8.0 
Component:  quadratic forms  Keywords:  sd87, Genus, sd91 
Cc:  Merged in:  
Authors:  Simon Brandhorst  Reviewers:  Anthony VárillyAlvarado, Jen Berg 
Report Upstream:  N/A  Work issues:  
Branch:  24a5b0b (Commits, GitHub, GitLab)  Commit:  
Dependencies:  Stopgaps: 
Description (last modified by )
sage: D4 = QuadraticForm(Matrix(ZZ,4,4,[2,0,0,1,0,2,0,1,0,0,2,1,1,1,1,2])) sage: G = D4.global_genus_symbol() sage: sage.quadratic_forms.genera.genus.is_GlobalGenus(G) True sage: G == copy(G) True sage: sage.quadratic_forms.genera.genus.is_GlobalGenus(G) False
The reason is that various functions unintentionally modify their input. Since a genus consists of lists containing lists, functions do just copy the lists but not deepcopy.
For example sage.quadratic_forms.genera.genus.canonical_2_adic_reduction modifies its input which does not seem to be intended.
Change History (16)
comment:1 Changed 4 years ago by
 Branch set to u/sbrandhorst/equality_testing_of_genera_of_quadratic_forms_over_zz_changes_the_genus_and_produces_false_results
comment:2 Changed 4 years ago by
 Commit set to 88bdf3c89c5522df62d0035cd3d8826755d451d2
 Status changed from new to needs_review
comment:3 Changed 4 years ago by
 Status changed from needs_review to needs_work
comment:4 Changed 4 years ago by
 Commit changed from 88bdf3c89c5522df62d0035cd3d8826755d451d2 to 8e62210714bf1bcc426733eab9848bd3ff230c23
Branch pushed to git repo; I updated commit sha1. New commits:
8e62210  Seems that is_2_adic_genus did not assume the input to be canonical but instead did not reduce the determinants mod 8. Changed that.

comment:5 Changed 4 years ago by
 Status changed from needs_work to needs_review
comment:7 Changed 4 years ago by
 Keywords sd87 added
comment:8 Changed 4 years ago by
 Keywords sd91 added; sd87 removed
comment:10 Changed 3 years ago by
 Status changed from needs_review to needs_work
Doesn't follow the doctest conventions; needs empty line after TESTS::
comment:11 Changed 3 years ago by
 Commit changed from 8e62210714bf1bcc426733eab9848bd3ff230c23 to 24a5b0bcc3f31e1dcf08ce88c0c709578a8bbf7c
comment:12 Changed 3 years ago by
 Status changed from needs_work to positive_review
Fix looks good now. Passes all doc tests and documentation builds.
comment:13 Changed 3 years ago by
 Status changed from positive_review to needs_work
Reviewer name is missing...
comment:14 Changed 3 years ago by
 Reviewers set to Anthony VarillyAlvarado, Jen Berg
 Status changed from needs_work to positive_review
Added reviewer names.
comment:15 Changed 3 years ago by
 Branch changed from u/sbrandhorst/equality_testing_of_genera_of_quadratic_forms_over_zz_changes_the_genus_and_produces_false_results to 24a5b0bcc3f31e1dcf08ce88c0c709578a8bbf7c
 Resolution set to fixed
 Status changed from positive_review to closed
comment:16 Changed 3 years ago by
 Commit 24a5b0bcc3f31e1dcf08ce88c0c709578a8bbf7c deleted
 Reviewers changed from Anthony VarillyAlvarado, Jen Berg to Anthony VárillyAlvarado, Jen Berg
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New commits:
Fixed two bugs in the genus class