Redefine objective sense as a proper IntEnum

doc/OnlineDocs/library_reference/common/enums.rst

@@ -0,0 +1,7 @@
+
+pyomo.common.enums
+==================
+
+.. automodule:: pyomo.common.enums
+   :members:
+   :member-order: bysource

doc/OnlineDocs/library_reference/common/index.rst

@@ -11,6 +11,7 @@ or rely on any other parts of Pyomo.
    config.rst
    dependencies.rst
    deprecation.rst
+   enums.rst
    errors.rst
    fileutils.rst
    formatting.rst

examples/pyomobook/pyomo-components-ch/obj_declaration.txt

@@ -55,7 +55,7 @@ Model unknown
     None
 value
 x[Q] + 2*x[R]
-1
+minimize
 6.5
 Model unknown
 

pyomo/common/enums.py

@@ -0,0 +1,162 @@
+#  ___________________________________________________________________________
+#
+#  Pyomo: Python Optimization Modeling Objects
+#  Copyright (c) 2008-2024
+#  National Technology and Engineering Solutions of Sandia, LLC
+#  Under the terms of Contract DE-NA0003525 with National Technology and
+#  Engineering Solutions of Sandia, LLC, the U.S. Government retains certain
+#  rights in this software.
+#  This software is distributed under the 3-clause BSD License.
+#  ___________________________________________________________________________
+
+"""This module provides standard :py:class:`enum.Enum` definitions used in
+Pyomo, along with additional utilities for working with custom Enums
+
+Utilities:
+
+.. autosummary::
+
+   ExtendedEnumType
+
+Standard Enums:
+
+.. autosummary::
+
+   ObjectiveSense
+
+"""
+
+import enum
+import itertools
+import sys
+
+if sys.version_info[:2] < (3, 11):
+    _EnumType = enum.EnumMeta
+else:
+    _EnumType = enum.EnumType
+
+
+class ExtendedEnumType(_EnumType):
+    """Metaclass for creating an :py:class:`enum.Enum` that extends another Enum
+
+    In general, :py:class:`enum.Enum` classes are not extensible: that is,
+    they are frozen when defined and cannot be the base class of another
+    Enum.  This Metaclass provides a workaround for creating a new Enum
+    that extends an existing enum.  Members in the base Enum are all
+    present as members on the extended enum.
+
+    Example
+    -------
+
+    .. testcode::
+       :hide:
+
+       import enum
+       from pyomo.common.enums import ExtendedEnumType
+
+    .. testcode::
+
+       class ObjectiveSense(enum.IntEnum):
+           minimize = 1
+           maximize = -1
+
+       class ProblemSense(enum.IntEnum, metaclass=ExtendedEnumType):
+           __base_enum__ = ObjectiveSense
+
+           unknown = 0
+
+    .. doctest::
+
+       >>> list(ProblemSense)
+       [<ProblemSense.unknown: 0>, <ObjectiveSense.minimize: 1>, <ObjectiveSense.maximize: -1>]
+       >>> ProblemSense.unknown
+       <ProblemSense.unknown: 0>
+       >>> ProblemSense.maximize
+       <ObjectiveSense.maximize: -1>
+       >>> ProblemSense(0)
+       <ProblemSense.unknown: 0>
+       >>> ProblemSense(1)
+       <ObjectiveSense.minimize: 1>
+       >>> ProblemSense('unknown')
+       <ProblemSense.unknown: 0>
+       >>> ProblemSense('maximize')
+       <ObjectiveSense.maximize: -1>
+       >>> hasattr(ProblemSense, 'minimize')
+       True
+       >>> ProblemSense.minimize is ObjectiveSense.minimize
+       True
+       >>> ProblemSense.minimize in ProblemSense
+       True
+
+    """
+
+    def __getattr__(cls, attr):
+        try:
+            return getattr(cls.__base_enum__, attr)
+        except:
+            return super().__getattr__(attr)
+
+    def __iter__(cls):
+        # The members of this Enum are the base enum members joined with
+        # the local members
+        return itertools.chain(super().__iter__(), cls.__base_enum__.__iter__())
+
+    def __contains__(cls, member):
+        # This enum "contains" both its local members and the members in
+        # the __base_enum__ (necessary for good auto-enum[sphinx] docs)
+        return super().__contains__(member) or member in cls.__base_enum__
+
+    def __instancecheck__(cls, instance):
+        if cls.__subclasscheck__(type(instance)):
+            return True
+        # Also pretend that members of the extended enum are subclasses
+        # of the __base_enum__.  This is needed to circumvent error
+        # checking in enum.__new__ (e.g., for `ProblemSense('minimize')`)
+        return cls.__base_enum__.__subclasscheck__(type(instance))
+
+    def _missing_(cls, value):
+        # Support attribute lookup by value or name
+        for attr in ('value', 'name'):
+            for member in cls:
+                if getattr(member, attr) == value:
+                    return member
+        return None
+
+    def __new__(metacls, cls, bases, classdict, **kwds):
+        # Support lookup by name - but only if the new Enum doesn't
+        # specify its own implementation of _missing_
+        if '_missing_' not in classdict:
+            classdict['_missing_'] = classmethod(ExtendedEnumType._missing_)
+        return super().__new__(metacls, cls, bases, classdict, **kwds)
+
+
+class ObjectiveSense(enum.IntEnum):
+    """Flag indicating if an objective is minimizing (1) or maximizing (-1).
+
+    While the numeric values are arbitrary, there are parts of Pyomo
+    that rely on this particular choice of value.  These values are also
+    consistent with some solvers (notably Gurobi).
+
+    """
+
+    minimize = 1
+    maximize = -1
+
+    # Overloading __str__ is needed to match the behavior of the old
+    # pyutilib.enum class (removed June 2020). There are spots in the
+    # code base that expect the string representation for items in the
+    # enum to not include the class name. New uses of enum shouldn't
+    # need to do this.
+    def __str__(self):
+        return self.name
+
+    @classmethod
+    def _missing_(cls, value):
+        for member in cls:
+            if member.name == value:
+                return member
+        return None
+
+
+minimize = ObjectiveSense.minimize
+maximize = ObjectiveSense.maximize

pyomo/common/tests/test_enums.py

@@ -0,0 +1,97 @@
+#  ___________________________________________________________________________
+#
+#  Pyomo: Python Optimization Modeling Objects
+#  Copyright (c) 2008-2024
+#  National Technology and Engineering Solutions of Sandia, LLC
+#  Under the terms of Contract DE-NA0003525 with National Technology and
+#  Engineering Solutions of Sandia, LLC, the U.S. Government retains certain
+#  rights in this software.
+#  This software is distributed under the 3-clause BSD License.
+#  ___________________________________________________________________________
+
+import enum
+
+import pyomo.common.unittest as unittest
+
+from pyomo.common.enums import ExtendedEnumType, ObjectiveSense
+
+
+class ProblemSense(enum.IntEnum, metaclass=ExtendedEnumType):
+    __base_enum__ = ObjectiveSense
+
+    unknown = 0
+
+
+class TestExtendedEnumType(unittest.TestCase):
+    def test_members(self):
+        self.assertEqual(
+            list(ProblemSense),
+            [ProblemSense.unknown, ObjectiveSense.minimize, ObjectiveSense.maximize],
+        )
+
+    def test_isinstance(self):
+        self.assertIsInstance(ProblemSense.unknown, ProblemSense)
+        self.assertIsInstance(ProblemSense.minimize, ProblemSense)
+        self.assertIsInstance(ProblemSense.maximize, ProblemSense)
+
+        self.assertTrue(ProblemSense.__instancecheck__(ProblemSense.unknown))
+        self.assertTrue(ProblemSense.__instancecheck__(ProblemSense.minimize))
+        self.assertTrue(ProblemSense.__instancecheck__(ProblemSense.maximize))
+
+    def test_getattr(self):
+        self.assertIs(ProblemSense.unknown, ProblemSense.unknown)
+        self.assertIs(ProblemSense.minimize, ObjectiveSense.minimize)
+        self.assertIs(ProblemSense.maximize, ObjectiveSense.maximize)
+
+    def test_hasattr(self):
+        self.assertTrue(hasattr(ProblemSense, 'unknown'))
+        self.assertTrue(hasattr(ProblemSense, 'minimize'))
+        self.assertTrue(hasattr(ProblemSense, 'maximize'))
+
+    def test_call(self):
+        self.assertIs(ProblemSense(0), ProblemSense.unknown)
+        self.assertIs(ProblemSense(1), ObjectiveSense.minimize)
+        self.assertIs(ProblemSense(-1), ObjectiveSense.maximize)
+
+        self.assertIs(ProblemSense('unknown'), ProblemSense.unknown)
+        self.assertIs(ProblemSense('minimize'), ObjectiveSense.minimize)
+        self.assertIs(ProblemSense('maximize'), ObjectiveSense.maximize)
+
+        with self.assertRaisesRegex(ValueError, "'foo' is not a valid ProblemSense"):
+            ProblemSense('foo')
+        with self.assertRaisesRegex(ValueError, "2 is not a valid ProblemSense"):
+            ProblemSense(2)
+
+    def test_contains(self):
+        self.assertIn(ProblemSense.unknown, ProblemSense)
+        self.assertIn(ProblemSense.minimize, ProblemSense)
+        self.assertIn(ProblemSense.maximize, ProblemSense)
+
+        self.assertNotIn(ProblemSense.unknown, ObjectiveSense)
+        self.assertIn(ProblemSense.minimize, ObjectiveSense)
+        self.assertIn(ProblemSense.maximize, ObjectiveSense)
+
+
+class TestObjectiveSense(unittest.TestCase):
+    def test_members(self):
+        self.assertEqual(
+            list(ObjectiveSense), [ObjectiveSense.minimize, ObjectiveSense.maximize]
+        )
+
+    def test_hasattr(self):
+        self.assertTrue(hasattr(ProblemSense, 'minimize'))
+        self.assertTrue(hasattr(ProblemSense, 'maximize'))
+
+    def test_call(self):
+        self.assertIs(ObjectiveSense(1), ObjectiveSense.minimize)
+        self.assertIs(ObjectiveSense(-1), ObjectiveSense.maximize)
+
+        self.assertIs(ObjectiveSense('minimize'), ObjectiveSense.minimize)
+        self.assertIs(ObjectiveSense('maximize'), ObjectiveSense.maximize)
+
+        with self.assertRaisesRegex(ValueError, "'foo' is not a valid ObjectiveSense"):
+            ObjectiveSense('foo')
+
+    def test_str(self):
+        self.assertEqual(str(ObjectiveSense.minimize), 'minimize')
+        self.assertEqual(str(ObjectiveSense.maximize), 'maximize')

pyomo/contrib/mindtpy/algorithm_base_class.py

@@ -27,13 +27,7 @@
 from operator import itemgetter
 from pyomo.common.errors import DeveloperError
 from pyomo.solvers.plugins.solvers.gurobi_direct import gurobipy
-from pyomo.opt import (
-    SolverFactory,
-    SolverResults,
-    ProblemSense,
-    SolutionStatus,
-    SolverStatus,
-)
+from pyomo.opt import SolverFactory, SolverResults, SolutionStatus, SolverStatus
 from pyomo.core import (
     minimize,
     maximize,
@@ -633,9 +627,7 @@ def process_objective(self, update_var_con_list=True):
             raise ValueError('Model has multiple active objectives.')
         else:
             main_obj = active_objectives[0]
-        self.results.problem.sense = (
-            ProblemSense.minimize if main_obj.sense == 1 else ProblemSense.maximize
-        )
+        self.results.problem.sense = main_obj.sense
         self.objective_sense = main_obj.sense
 
         # Move the objective to the constraints if it is nonlinear or move_objective is True.

pyomo/contrib/mindtpy/util.py

@@ -29,7 +29,6 @@
 from pyomo.contrib.mcpp.pyomo_mcpp import mcpp_available, McCormick
 from pyomo.contrib.fbbt.fbbt import compute_bounds_on_expr
 import pyomo.core.expr as EXPR
-from pyomo.opt import ProblemSense
 from pyomo.contrib.gdpopt.util import get_main_elapsed_time, time_code
 from pyomo.util.model_size import build_model_size_report
 from pyomo.common.dependencies import attempt_import

pyomo/contrib/pynumero/algorithms/solvers/cyipopt_solver.py

@@ -65,7 +65,7 @@
 from pyomo.common.config import ConfigBlock, ConfigValue
 from pyomo.common.timing import TicTocTimer
 from pyomo.core.base import Block, Objective, minimize
-from pyomo.opt import SolverStatus, SolverResults, TerminationCondition, ProblemSense
+from pyomo.opt import SolverStatus, SolverResults, TerminationCondition
 from pyomo.opt.results.solution import Solution
 
 logger = logging.getLogger(__name__)
@@ -447,11 +447,10 @@ def solve(self, model, **kwds):
 
         results.problem.name = model.name
         obj = next(model.component_data_objects(Objective, active=True))
+        results.problem.sense = obj.sense
         if obj.sense == minimize:
-            results.problem.sense = ProblemSense.minimize
             results.problem.upper_bound = info["obj_val"]
         else:
-            results.problem.sense = ProblemSense.maximize
             results.problem.lower_bound = info["obj_val"]
         results.problem.number_of_objectives = 1
         results.problem.number_of_constraints = ng

pyomo/core/__init__.py

@@ -101,7 +101,7 @@
     BooleanValue,
     native_logical_values,
 )
-from pyomo.core.kernel.objective import minimize, maximize
+from pyomo.core.base import minimize, maximize
 from pyomo.core.base.config import PyomoOptions
 
 from pyomo.core.base.expression import Expression

pyomo/core/base/__init__.py

@@ -12,6 +12,7 @@
 # TODO: this import is for historical backwards compatibility and should
 # probably be removed
 from pyomo.common.collections import ComponentMap
+from pyomo.common.enums import minimize, maximize
 
 from pyomo.core.expr.symbol_map import SymbolMap
 from pyomo.core.expr.numvalue import (
@@ -33,7 +34,6 @@
     BooleanValue,
     native_logical_values,
 )
-from pyomo.core.kernel.objective import minimize, maximize
 from pyomo.core.base.config import PyomoOptions
 
 from pyomo.core.base.expression import Expression, _ExpressionData