Opened 5 years ago
Closed 5 years ago
#20184 closed defect (fixed)
Comparison of number field elements embedded into RIF fails
Reported by: | mkoeppe | Owned by: | |
---|---|---|---|
Priority: | major | Milestone: | sage-7.2 |
Component: | number fields | Keywords: | |
Cc: | tmonteil, jj, sstarosta, gagern, mkoeppe, vdelecroix | Merged in: | |
Authors: | Matthias Koeppe | Reviewers: | Dima Pasechnik |
Report Upstream: | N/A | Work issues: | |
Branch: | 259afd9 (Commits) | Commit: | 259afd9503782367bfd611584f1ca675e4839717 |
Dependencies: | Stopgaps: |
Description
This is a follow-up on #17830, which made this possible:
sage: x = polygen(ZZ) sage: K.<cbrt2> = NumberField(x^3 - 2, embedding=AA.polynomial_root(x^3-2, RIF(0,3))) sage: 6064/4813 < cbrt2 < 90325/71691 True
However, if I embed into a RIF instead, the same test fails.
sage: x = polygen(ZZ) sage: K.<cbrt2> = NumberField(x^3 - 2, embedding=RIF(AA.polynomial_root(x^3-2, RIF(0,3)))) sage: 6064/4813 < cbrt2 < 90325/71691 False
Change History (6)
comment:1 Changed 5 years ago by
comment:2 Changed 5 years ago by
- Milestone changed from sage-7.1 to sage-duplicate/invalid/wontfix
- Status changed from new to needs_review
I tend to agree with Vincent.
comment:3 Changed 5 years ago by
- Branch set to u/mkoeppe/comparison_of_number_field_elements_embedded_into_rif_fails
comment:4 Changed 5 years ago by
- Commit set to 259afd9503782367bfd611584f1ca675e4839717
- Milestone changed from sage-duplicate/invalid/wontfix to sage-7.2
Thanks for the discussion; I agree that it's a plausible restriction.
I have added a patch that adds this detail to the documentation of NumberField
.
New commits:
259afd9 | Document implementation restriction of comparison of real number field elements
|
comment:5 Changed 5 years ago by
- Reviewers set to Dima Pasechnik
- Status changed from needs_review to positive_review
a bit of extra doc never hurts.
comment:6 Changed 5 years ago by
- Branch changed from u/mkoeppe/comparison_of_number_field_elements_embedded_into_rif_fails to 259afd9503782367bfd611584f1ca675e4839717
- Resolution set to fixed
- Status changed from positive_review to closed
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I do not think this is a bug.
The (respective to the embedding) comparison code is used only if there is a coercion embedding for which the codomain allows to have arbitrary precision real intervals (right now, only
AA
/QQbar
but could be extend toRLF
/CLF
). I do not mean that it is not feasible to find the corresponding exact embedding from a one intoRIF
one. But I would be against using it.What is the problem with the behavior in the ticket description?