Redefine objective sense as a proper IntEnum
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…y match what is advertised in the Book
jsiirola
changed the title
IntEnumIntEnum
mrmundt
reviewed
Apr 4, 2024
mrmundt
reviewed
Apr 4, 2024
mrmundt
approved these changes
Apr 9, 2024
emma58
approved these changes
Apr 17, 2024
| if results.problem.sense == ProblemSense.minimize: | ||
| if results.solver.primal_bound < results.solver.dual_bound: | ||
| results.problem.lower_bound = results.solver.primal_bound | ||
| results.problem.upper_bound = results.solver.dual_bound | ||
| else: | ||
| results.problem.lower_bound = results.solver.dual_bound | ||
| results.problem.upper_bound = results.solver.primal_bound |
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Can this go wrong if your bounds cross by a little bit?
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Yes - you probably can. This will be easily fixable in the new solver interfaces (where the results parser can have easier access to the original model and won't have to guess about the sense), but there isn't an obvious better solution here (unless the scip output log prints something about the sense - but I really don't want to put more dependence on the parsing of output logs).
blnicho
approved these changes
Apr 23, 2024
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Fixes #993 .
Summary/Motivation:
There have been some longstanding inconsistencies regarding how we manage the definition of "objective sense" in Pyomo. The results object uses an Enum with 3 values (minimize, maximize, and unknown). In the modeling side, we make heavy use of two named constants (
minimizeandmaximize). These constants are justints (1 and -1, respectively), and those constants are defined inpyomo.core.kernel.objective(causing one of the few inter-linkages between kernel and the AML).This PR defines a new Enum (
pyomo.common.enums.ObjectiveSense), and redefines theminimizeandmaximizeconstants to be the members of that Enum. To preserve consistency / backwards compatibility,ObjectiveSenseis anIntEnum, so the old constants / old usage does not need to change.ProblemSenseis now an extension ofObjectiveSensethat also admitsunknown. Unfortunately, due to the way that the old solvers are structured, it is not (easy) to remove the use ofunknownwhen processing results from the old solver interfaces. The compromise here is the development ofExtendedEnumType, which allows us to define extended (or derived) Enums that combine the enums from another class with additional locally-defined members - so theminimizeandmaximizemembers inProblemSenseare actually members ofObjectiveSense.Changes proposed in this PR:
ExtendedEnumTypemetaclass to support extended/derived EnumsObjectiveSenseenum (withminimizeandmaximizemembers)ProblemSenseto be an extension ofObjectiveSenseProblemSensefrom almost all of PyomoLegal Acknowledgement
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