#18742: interactive_simplex_method: Support several styles corresponding to
major
textbooks
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Reporter: mkoeppe | Owner:
Type: task | Status: needs_review
Priority: minor | Milestone: sage-6.8
Component: numerical | Resolution:
Keywords: beginner, lp, | Merged in:
teaching | Reviewers: Andrey Novoseltsev
Authors: Peijun Xiao, | Work issues:
Matthias Koeppe | Commit:
Report Upstream: N/A | 3fdf390c77a726cbbdcc899150823780348ac1f2
Branch: | Stopgaps:
u/mkoeppe/interactive_simplex_method__support_several_styles_corresponding_to_major_textbooks|
Dependencies: |
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Comment (by mkoeppe):
Replying to [comment:18 novoselt]:
> Also I am not sure if you have noticed, but there are 4 types of
problems: "max", "min", and "-max", "-min". Do you want to always set up
dictionaries for maximization and put minus sign in front of its objective
depending on whether the constant term of the "objective expression" is
the actual value or not? Then it should be (say) "z" for "max" and "-min"
and "-z" for "-max" and "min". If this sounds reasonable, I'll make this
change for both styles, so that only actual naming of the variable is
different.
In Vanderbei, primal dictionaries are always "max zeta", and dual
dictionaries are always "-max -xi".
The other cases do not appear; so any decision what to do with those will
be consistent and fine with me.
> Follow up to the previous - if you are unhappy with plain `objective`,
how about `dictionary_objective` or `objective_name` instead? Calling
expressions potentially including negative signs `objective_variable`
seems confusing. Also, not insisting on plain names allows for adding
constant terms to objective in the future.
"objective_name" sounds fine to me. With "objective", I think there is a
risk of confusion with the objective coefficients.
In comment 17, you wrote:
> there was already objective parameter for problems in standard form.
Renaming it to objective_variable and changing its place is a backward-
incompatible change which is not worth the effort, I think. How about I
revert to objective where it was in place, and change objective_variable
to objective where it is new for consistency?
If you are really concerned about backwards incompatibility for this code,
then this solution as your propose would seem fine.
--
Ticket URL: <http://trac.sagemath.org/ticket/18742#comment:19>
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