#11607: read constraints from linear program
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Reporter: john_perry | Owner: ncohen
Type: enhancement | Status: needs_info
Priority: major | Milestone: sage-4.7.2
Component: linear programming | Keywords: sd32
Work_issues: | Upstream: N/A
Reviewer: | Author: john_perry
Merged: | Dependencies:
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Changes (by ncohen):
* status: needs_review => needs_info
Comment:
Hello John !
I don't think the row and row_bounds method as they are implemented can be
very useful to the user. They gave you access to the information of a
constraint and take as an input the line number, but the user has for the
moment no way whatsoever to know the number of a constraint. I mean, when
would the user want to obtain the constraint corresponding to a constraint
he does not know already, for instance obtained through your
get_constraints method ?
I think those method, if you think they may beuseful by themselves, would
make more sense in the generic_backend module. As all the other backends
extend it, it would be available for ach backend, and could be used by
your get_constraints method, it would make more sese at this level.
I have a similar remark for the get_constraints method. It returns a
constraint as a list of indices and coefficient, but the indices have no
meaning for the user who only deals with symbolic variables. Instead of
returning vectors of indces and coefficient, which is the canonical form
used by the solver's C API, what about returning a dictionary associating
to each symbolic its coefficient ? This way the user can easily test
whether the coefficient of one given variable is nonzero in the
constraint, etc... `:-)`
Nathann
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11607#comment:3>
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