#20337: MIP: Several fixes regarding constant terms in the objective function
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Reporter: mkoeppe | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-7.2
Component: numerical | Resolution:
Keywords: lp | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/mkoeppe/mip_backends__obj_constant_term_should_be_exposed_by_a_backend_method|
ad40508934049090580c678ec4249588273b43cf
Dependencies: | Stopgaps:
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Changes (by mkoeppe):
* status: new => needs_review
* commit: => ad40508934049090580c678ec4249588273b43cf
Old description:
> ... rather than being accessed directly in
> `MixedIntegerLinearProgram.show`
New description:
Contrary to documentation, one cannot set a constantly zero objective
function by passing 0 to `set_objective`.
{{{
sage: p = MixedIntegerLinearProgram(maximization=True)
sage: x = p.new_variable(nonnegative=True)
sage: p.set_objective(0)
AttributeError: 'sage.rings.integer.Integer' object has no attribute
'dict'
}}}
This ticket fixes that and actually allows any field number (which ends up
in the `obj_constant_term`).
Moreover, the backend slot `obj_constant_term` is accessed directly by
`MixedIntegerLinearProgram.show`; it should instead be exposed by a
backend method, which this ticket adds as well.
Finally, the `show` method added an extraneous blank line when a nonzero
`obj_constant_term` was present. Fixed and doctest added.
--
Comment:
New commits:
||[http://git.sagemath.org/sage.git/commit/?id=62a4da07df2c7c000b2fb22b96e5c493b5976c20
62a4da0]||{{{objective_constant_term: New MIP backend method}}}||
||[http://git.sagemath.org/sage.git/commit/?id=edb9d7f795f8254571a2f060eb1c49d6012bb9f3
edb9d7f]||{{{MixedIntegerLinearProgram.show: Remove extraneous blank line
when objective constant term is nonzero; add doctest}}}||
||[http://git.sagemath.org/sage.git/commit/?id=ad40508934049090580c678ec4249588273b43cf
ad40508]||{{{MixedIntegerLinearProgram.set_objective: Accept constants as
objective}}}||
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Ticket URL: <http://trac.sagemath.org/ticket/20337#comment:2>
Sage <http://www.sagemath.org>
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