Opened 6 years ago
Closed 6 years ago
#14238 closed enhancement (fixed)
a polyhedron() method for Linear Programs
Reported by: | ncohen | Owned by: | ncohen |
---|---|---|---|
Priority: | major | Milestone: | sage-5.9 |
Component: | linear programming | Keywords: | |
Cc: | dimpase, dcoudert, nthiery, vbraun | Merged in: | sage-5.9.beta0 |
Authors: | Nathann Cohen | Reviewers: | Dmitrii Pasechnik |
Report Upstream: | N/A | Work issues: | |
Branch: | Commit: | ||
Dependencies: | Stopgaps: |
Description
As the title says, this patch implements a .polyhedron()
method which returns the Polyhedron
object defined by the LP.
And some doc, while we are at it.
Nathann
Attachments (1)
Change History (10)
comment:1 Changed 6 years ago by
- Status changed from new to needs_review
comment:2 follow-up: ↓ 3 Changed 6 years ago by
- Status changed from needs_review to needs_work
comment:3 in reply to: ↑ 2 ; follow-up: ↓ 4 Changed 6 years ago by
- the original polyhedron described by the input
- the way it is represented by the backend invoked.
I don't see what you have in mind. The LP variables are internally numbered from 0 to n-1, that is also the case with the variables of a Polyhedron. With this, there is only ony way to define the constraints, isn't it ?
Nathann
comment:4 in reply to: ↑ 3 ; follow-up: ↓ 5 Changed 6 years ago by
Replying to ncohen:
- the original polyhedron described by the input
- the way it is represented by the backend invoked.
I don't see what you have in mind. The LP variables are internally numbered from 0 to n-1, that is also the case with the variables of a Polyhedron. With this, there is only ony way to define the constraints, isn't it ?
actually, you yourself pointed out to me, a while ago, a case where a backend (GUROBI?) does some nontrivial rewriting of a constraint, if I recall right, of the form a<=x_i<=b, resulting in adding a new variable, or something like this.
Dima
comment:5 in reply to: ↑ 4 Changed 6 years ago by
actually, you yourself pointed out to me, a while ago, a case where a backend (GUROBI?) does some nontrivial rewriting of a constraint, if I recall right, of the form a<=x_i<=b, resulting in adding a new variable, or something like this.
Arggggggggg... Right. I had totally forgotten about that. I will add a warning. I hate these hacks :-/
Nathann
comment:6 Changed 6 years ago by
- Status changed from needs_work to needs_review
Done ! Thanks for noticing that !
Nathann
comment:7 Changed 6 years ago by
- Status changed from needs_review to positive_review
comment:8 Changed 6 years ago by
- Reviewers set to Dmitrii Pasechnik
The patch needs a proper commit message.
Changed 6 years ago by
comment:9 Changed 6 years ago by
- Merged in set to sage-5.9.beta0
- Resolution set to fixed
- Status changed from positive_review to closed
I can think of two not always equal things this returns
Please clarify in the docs. Also, please add tests for unbounded and empty cases...