Use np.array for Variables.names

Makefile

@@ -2,7 +2,7 @@ PYTHON      := python3
 PYTEST      := pytest
 PIP         := $(PYTHON) -m pip
 MYPY        := $(PYTHON) -m mypy
-PYTEST_ARGS := -W ignore::DeprecationWarning -vv -x --log-level=DEBUG
+PYTEST_ARGS := -W ignore::DeprecationWarning -vv --log-level=DEBUG
 VERSION     := 0.2
 
 all: docs test

miplearn/components/primal.py

@@ -95,7 +95,7 @@ class PrimalSolutionComponent(Component):
         )
 
     def sample_predict(self, sample: Sample) -> Solution:
-        var_names = sample.get_vector("static_var_names")
+        var_names = sample.get_array("static_var_names")
         var_categories = sample.get_vector("static_var_categories")
         assert var_names is not None
         assert var_categories is not None
@@ -145,7 +145,7 @@ class PrimalSolutionComponent(Component):
         instance_features = sample.get_vector("static_instance_features")
         mip_var_values = sample.get_vector("mip_var_values")
         var_features = sample.get_vector_list("lp_var_features")
-        var_names = sample.get_vector("static_var_names")
+        var_names = sample.get_array("static_var_names")
         var_categories = sample.get_vector("static_var_categories")
         if var_features is None:
             var_features = sample.get_vector_list("static_var_features")
@@ -187,8 +187,8 @@ class PrimalSolutionComponent(Component):
         _: Optional[Instance],
         sample: Sample,
     ) -> Dict[str, Dict[str, float]]:
-        mip_var_values = sample.get_vector("mip_var_values")
+        mip_var_values = sample.get_array("mip_var_values")
-        var_names = sample.get_vector("static_var_names")
+        var_names = sample.get_array("static_var_names")
         assert mip_var_values is not None
         assert var_names is not None
 

miplearn/features/extractor.py

@@ -5,7 +5,7 @@
 import collections
 import numbers
 from math import log, isfinite
-from typing import TYPE_CHECKING, Dict, Optional, List, Any, Tuple
+from typing import TYPE_CHECKING, Dict, Optional, List, Any, Tuple, KeysView, cast
 
 import numpy as np
 
@@ -34,7 +34,7 @@ class FeaturesExtractor:
         variables = solver.get_variables(with_static=True)
         constraints = solver.get_constraints(with_static=True, with_lhs=self.with_lhs)
         sample.put_array("static_var_lower_bounds", variables.lower_bounds)
-        sample.put_vector("static_var_names", variables.names)
+        sample.put_array("static_var_names", variables.names)
         sample.put_array("static_var_obj_coeffs", variables.obj_coeffs)
         sample.put_vector("static_var_types", variables.types)
         sample.put_array("static_var_upper_bounds", variables.upper_bounds)
@@ -139,12 +139,29 @@ class FeaturesExtractor:
         instance: "Instance",
         sample: Sample,
     ) -> Tuple[List, List]:
-        categories: List[Optional[str]] = []
+        # Query variable names
-        user_features: List[Optional[List[float]]] = []
+        var_names = sample.get_array("static_var_names")
-        var_features_dict = instance.get_variable_features()
-        var_categories_dict = instance.get_variable_categories()
-        var_names = sample.get_vector("static_var_names")
         assert var_names is not None
+
+        # Query variable features and categories
+        var_features_dict = {
+            v.encode(): f for (v, f) in instance.get_variable_features().items()
+        }
+        var_categories_dict = {
+            v.encode(): f for (v, f) in instance.get_variable_categories().items()
+        }
+
+        # Assert that variables in user-provided dicts actually exist
+        var_names_set = set(var_names)
+        for keys in [var_features_dict.keys(), var_categories_dict.keys()]:
+            for vn in cast(KeysView, keys):
+                assert (
+                    vn in var_names_set
+                ), f"Variable {vn!r} not found in the problem; {var_names_set}"
+
+        # Assemble into compact lists
+        user_features: List[Optional[List[float]]] = []
+        categories: List[Optional[str]] = []
         for (i, var_name) in enumerate(var_names):
             if var_name not in var_categories_dict:
                 user_features.append(None)

miplearn/solvers/gurobi.py

@@ -73,11 +73,11 @@ class GurobiSolver(InternalSolver):
         self._has_lp_solution = False
         self._has_mip_solution = False
 
-        self._varname_to_var: Dict[str, "gurobipy.Var"] = {}
+        self._varname_to_var: Dict[bytes, "gurobipy.Var"] = {}
         self._cname_to_constr: Dict[str, "gurobipy.Constr"] = {}
         self._gp_vars: List["gurobipy.Var"] = []
         self._gp_constrs: List["gurobipy.Constr"] = []
-        self._var_names: List[str] = []
+        self._var_names: np.ndarray = np.empty(0)
         self._constr_names: List[str] = []
         self._var_types: List[str] = []
         self._var_lbs: np.ndarray = np.empty(0)
@@ -263,11 +263,13 @@ class GurobiSolver(InternalSolver):
         if self.cb_where is not None:
             if self.cb_where == self.gp.GRB.Callback.MIPNODE:
                 return {
-                    v.varName: self.model.cbGetNodeRel(v) for v in self.model.getVars()
+                    v.varName.encode(): self.model.cbGetNodeRel(v)
+                    for v in self.model.getVars()
                 }
             elif self.cb_where == self.gp.GRB.Callback.MIPSOL:
                 return {
-                    v.varName: self.model.cbGetSolution(v) for v in self.model.getVars()
+                    v.varName.encode(): self.model.cbGetSolution(v)
+                    for v in self.model.getVars()
                 }
             else:
                 raise Exception(
@@ -276,7 +278,7 @@ class GurobiSolver(InternalSolver):
                 )
         if self.model.solCount == 0:
             return None
-        return {v.varName: v.x for v in self.model.getVars()}
+        return {v.varName.encode(): v.x for v in self.model.getVars()}
 
     @overrides
     def get_variable_attrs(self) -> List[str]:
@@ -584,7 +586,10 @@ class GurobiSolver(InternalSolver):
         assert self.model is not None
         gp_vars: List["gurobipy.Var"] = self.model.getVars()
         gp_constrs: List["gurobipy.Constr"] = self.model.getConstrs()
-        var_names: List[str] = self.model.getAttr("varName", gp_vars)
+        var_names: np.ndarray = np.array(
+            self.model.getAttr("varName", gp_vars),
+            dtype="S",
+        )
         var_types: List[str] = self.model.getAttr("vtype", gp_vars)
         var_ubs: np.ndarray = np.array(
             self.model.getAttr("ub", gp_vars),
@@ -599,7 +604,7 @@ class GurobiSolver(InternalSolver):
             dtype=float,
         )
         constr_names: List[str] = self.model.getAttr("constrName", gp_constrs)
-        varname_to_var: Dict = {}
+        varname_to_var: Dict[bytes, "gurobipy.Var"] = {}
         cname_to_constr: Dict = {}
         for (i, gp_var) in enumerate(gp_vars):
             assert var_names[i] not in varname_to_var, (

miplearn/solvers/internal.py

@@ -50,7 +50,7 @@ class MIPSolveStats:
 
 @dataclass
 class Variables:
-    names: Optional[List[str]] = None
+    names: Optional[np.ndarray] = None
     basis_status: Optional[List[str]] = None
     lower_bounds: Optional[np.ndarray] = None
     obj_coeffs: Optional[np.ndarray] = None
@@ -71,7 +71,7 @@ class Constraints:
     basis_status: Optional[List[str]] = None
     dual_values: Optional[np.ndarray] = None
     lazy: Optional[List[bool]] = None
-    lhs: Optional[List[List[Tuple[str, float]]]] = None
+    lhs: Optional[List[List[Tuple[bytes, float]]]] = None
     names: Optional[List[str]] = None
     rhs: Optional[np.ndarray] = None
     sa_rhs_down: Optional[np.ndarray] = None

miplearn/solvers/pyomo/base.py

@@ -34,8 +34,6 @@ from miplearn.types import (
     SolverParams,
     UserCutCallback,
     Solution,
-    VariableName,
-    Category,
 )
 
 logger = logging.getLogger(__name__)
@@ -59,7 +57,7 @@ class BasePyomoSolver(InternalSolver):
         self._is_warm_start_available: bool = False
         self._pyomo_solver: SolverFactory = solver_factory
         self._obj_sense: str = "min"
-        self._varname_to_var: Dict[str, pe.Var] = {}
+        self._varname_to_var: Dict[bytes, pe.Var] = {}
         self._cname_to_constr: Dict[str, pe.Constraint] = {}
         self._termination_condition: str = ""
         self._has_lp_solution = False
@@ -166,7 +164,7 @@ class BasePyomoSolver(InternalSolver):
 
         names: List[str] = []
         rhs: List[float] = []
-        lhs: List[List[Tuple[str, float]]] = []
+        lhs: List[List[Tuple[bytes, float]]] = []
         senses: List[str] = []
         dual_values: List[float] = []
         slacks: List[float] = []
@@ -199,18 +197,18 @@ class BasePyomoSolver(InternalSolver):
                             if isinstance(term, MonomialTermExpression):
                                 lhsc.append(
                                     (
-                                        term._args_[1].name,
+                                        term._args_[1].name.encode(),
                                         float(term._args_[0]),
                                     )
                                 )
                             elif isinstance(term, _GeneralVarData):
-                                lhsc.append((term.name, 1.0))
+                                lhsc.append((term.name.encode(), 1.0))
                             else:
                                 raise Exception(
                                     f"Unknown term type: {term.__class__.__name__}"
                                 )
                     elif isinstance(expr, _GeneralVarData):
-                        lhsc.append((expr.name, 1.0))
+                        lhsc.append((expr.name.encode(), 1.0))
                     else:
                         raise Exception(
                             f"Unknown expression type: {expr.__class__.__name__}"
@@ -264,7 +262,7 @@ class BasePyomoSolver(InternalSolver):
             for index in var:
                 if var[index].fixed:
                     continue
-                solution[f"{var}[{index}]"] = var[index].value
+                solution[f"{var}[{index}]".encode()] = var[index].value
         return solution
 
     @overrides
@@ -328,7 +326,7 @@ class BasePyomoSolver(InternalSolver):
                     values.append(v.value)
 
         return Variables(
-            names=_none_if_empty(names),
+            names=_none_if_empty(np.array(names, dtype="S")),
             types=_none_if_empty(types),
             upper_bounds=_none_if_empty(np.array(upper_bounds, dtype=float)),
             lower_bounds=_none_if_empty(np.array(lower_bounds, dtype=float)),
@@ -558,9 +556,9 @@ class BasePyomoSolver(InternalSolver):
         self._varname_to_var = {}
         for var in self.model.component_objects(Var):
             for idx in var:
-                varname = f"{var.name}[{idx}]"
+                varname = f"{var.name}[{idx}]".encode()
                 if idx is None:
-                    varname = var.name
+                    varname = var.name.encode()
                 self._varname_to_var[varname] = var[idx]
                 self._all_vars += [var[idx]]
                 if var[idx].domain == pyomo.core.base.set_types.Binary:

miplearn/solvers/tests/__init__.py

@@ -10,6 +10,7 @@ from miplearn.solvers.internal import InternalSolver, Variables, Constraints
 
 inf = float("inf")
 
+
 # NOTE:
 # This file is in the main source folder, so that it can be called from Julia.
 
@@ -40,7 +41,7 @@ def run_basic_usage_tests(solver: InternalSolver) -> None:
     assert_equals(
         solver.get_variables(),
         Variables(
-            names=["x[0]", "x[1]", "x[2]", "x[3]", "z"],
+            names=np.array(["x[0]", "x[1]", "x[2]", "x[3]", "z"], dtype="S"),
             lower_bounds=np.array([0.0, 0.0, 0.0, 0.0, 0.0]),
             upper_bounds=np.array([1.0, 1.0, 1.0, 1.0, 67.0]),
             types=["B", "B", "B", "B", "C"],
@@ -56,11 +57,11 @@ def run_basic_usage_tests(solver: InternalSolver) -> None:
             rhs=np.array([0.0]),
             lhs=[
                 [
-                    ("x[0]", 23.0),
+                    (b"x[0]", 23.0),
-                    ("x[1]", 26.0),
+                    (b"x[1]", 26.0),
-                    ("x[2]", 20.0),
+                    (b"x[2]", 20.0),
-                    ("x[3]", 18.0),
+                    (b"x[3]", 18.0),
-                    ("z", -1.0),
+                    (b"z", -1.0),
                 ],
             ],
             senses=["="],
@@ -83,7 +84,7 @@ def run_basic_usage_tests(solver: InternalSolver) -> None:
         _filter_attrs(
             solver.get_variable_attrs(),
             Variables(
-                names=["x[0]", "x[1]", "x[2]", "x[3]", "z"],
+                names=np.array(["x[0]", "x[1]", "x[2]", "x[3]", "z"], dtype="S"),
                 basis_status=["U", "B", "U", "L", "U"],
                 reduced_costs=np.array(
                     [193.615385, 0.0, 187.230769, -23.692308, 13.538462]
@@ -140,7 +141,7 @@ def run_basic_usage_tests(solver: InternalSolver) -> None:
         _filter_attrs(
             solver.get_variable_attrs(),
             Variables(
-                names=["x[0]", "x[1]", "x[2]", "x[3]", "z"],
+                names=np.array(["x[0]", "x[1]", "x[2]", "x[3]", "z"], dtype="S"),
                 values=np.array([1.0, 0.0, 1.0, 1.0, 61.0]),
             ),
         ),
@@ -161,7 +162,7 @@ def run_basic_usage_tests(solver: InternalSolver) -> None:
     # Build new constraint and verify that it is violated
     cf = Constraints(
         names=["cut"],
-        lhs=[[("x[0]", 1.0)]],
+        lhs=[[(b"x[0]", 1.0)]],
         rhs=np.array([0.0]),
         senses=["<"],
     )
@@ -178,14 +179,14 @@ def run_basic_usage_tests(solver: InternalSolver) -> None:
                 rhs=np.array([0.0, 0.0]),
                 lhs=[
                     [
-                        ("x[0]", 23.0),
+                        (b"x[0]", 23.0),
-                        ("x[1]", 26.0),
+                        (b"x[1]", 26.0),
-                        ("x[2]", 20.0),
+                        (b"x[2]", 20.0),
-                        ("x[3]", 18.0),
+                        (b"x[3]", 18.0),
-                        ("z", -1.0),
+                        (b"z", -1.0),
                     ],
                     [
-                        ("x[0]", 1.0),
+                        (b"x[0]", 1.0),
                     ],
                 ],
                 senses=["=", "<"],
@@ -208,16 +209,16 @@ def run_warm_start_tests(solver: InternalSolver) -> None:
     instance = solver.build_test_instance_knapsack()
     model = instance.to_model()
     solver.set_instance(instance, model)
-    solver.set_warm_start({"x[0]": 1.0, "x[1]": 0.0, "x[2]": 0.0, "x[3]": 1.0})
+    solver.set_warm_start({b"x[0]": 1.0, b"x[1]": 0.0, b"x[2]": 0.0, b"x[3]": 1.0})
     stats = solver.solve(tee=True)
     if stats.mip_warm_start_value is not None:
         assert_equals(stats.mip_warm_start_value, 725.0)
 
-    solver.set_warm_start({"x[0]": 1.0, "x[1]": 1.0, "x[2]": 1.0, "x[3]": 1.0})
+    solver.set_warm_start({b"x[0]": 1.0, b"x[1]": 1.0, b"x[2]": 1.0, b"x[3]": 1.0})
     stats = solver.solve(tee=True)
     assert stats.mip_warm_start_value is None
 
-    solver.fix({"x[0]": 1.0, "x[1]": 0.0, "x[2]": 0.0, "x[3]": 1.0})
+    solver.fix({b"x[0]": 1.0, b"x[1]": 0.0, b"x[2]": 0.0, b"x[3]": 1.0})
     stats = solver.solve(tee=True)
     assert_equals(stats.mip_lower_bound, 725.0)
     assert_equals(stats.mip_upper_bound, 725.0)
@@ -257,15 +258,15 @@ def run_lazy_cb_tests(solver: InternalSolver) -> None:
     def lazy_cb(cb_solver: InternalSolver, cb_model: Any) -> None:
         relsol = cb_solver.get_solution()
         assert relsol is not None
-        assert relsol["x[0]"] is not None
+        assert relsol[b"x[0]"] is not None
-        if relsol["x[0]"] > 0:
+        if relsol[b"x[0]"] > 0:
             instance.enforce_lazy_constraint(cb_solver, cb_model, "cut")
 
     solver.set_instance(instance, model)
     solver.solve(lazy_cb=lazy_cb)
     solution = solver.get_solution()
     assert solution is not None
-    assert_equals(solution["x[0]"], 0.0)
+    assert_equals(solution[b"x[0]"], 0.0)
 
 
 def _equals_preprocess(obj: Any) -> Any:
@@ -274,7 +275,7 @@ def _equals_preprocess(obj: Any) -> Any:
             return np.round(obj, decimals=6).tolist()
         else:
             return obj.tolist()
-    elif isinstance(obj, (int, str, bool, np.bool_)):
+    elif isinstance(obj, (int, str, bool, np.bool_, np.bytes_, bytes)):
         return obj
     elif isinstance(obj, float):
         return round(obj, 6)

miplearn/types.py

@@ -15,8 +15,7 @@ IterationCallback = Callable[[], bool]
 LazyCallback = Callable[[Any, Any], None]
 SolverParams = Dict[str, Any]
 UserCutCallback = Callable[["InternalSolver", Any], None]
-VariableName = str
+Solution = Dict[bytes, Optional[float]]
-Solution = Dict[VariableName, Optional[float]]
 
 LearningSolveStats = TypedDict(
     "LearningSolveStats",

tests/components/test_primal.py

@@ -22,7 +22,7 @@ from miplearn.solvers.tests import assert_equals
 def sample() -> Sample:
     sample = MemorySample(
         {
-            "static_var_names": ["x[0]", "x[1]", "x[2]", "x[3]"],
+            "static_var_names": np.array(["x[0]", "x[1]", "x[2]", "x[3]"], dtype="S"),
             "static_var_categories": ["default", None, "default", "default"],
             "mip_var_values": np.array([0.0, 1.0, 1.0, 0.0]),
             "static_instance_features": [5.0],
@@ -112,10 +112,10 @@ def test_usage() -> None:
 def test_evaluate(sample: Sample) -> None:
     comp = PrimalSolutionComponent()
     comp.sample_predict = lambda _: {  # type: ignore
-        "x[0]": 1.0,
+        b"x[0]": 1.0,
-        "x[1]": 1.0,
+        b"x[1]": 1.0,
-        "x[2]": 0.0,
+        b"x[2]": 0.0,
-        "x[3]": None,
+        b"x[3]": None,
     }
     ev = comp.sample_evaluate(None, sample)
     assert_equals(
@@ -150,8 +150,8 @@ def test_predict(sample: Sample) -> None:
     assert_array_equal(x["default"], clf.predict_proba.call_args[0][0])
     assert_array_equal(x["default"], thr.predict.call_args[0][0])
     assert pred == {
-        "x[0]": 0.0,
+        b"x[0]": 0.0,
-        "x[1]": None,
+        b"x[1]": None,
-        "x[2]": None,
+        b"x[2]": None,
-        "x[3]": 1.0,
+        b"x[3]": 1.0,
     }

tests/features/test_extractor.py

@@ -33,7 +33,7 @@ def test_knapsack() -> None:
     extractor.extract_after_load_features(instance, solver, sample)
     assert_equals(
         sample.get_vector("static_var_names"),
-        ["x[0]", "x[1]", "x[2]", "x[3]", "z"],
+        np.array(["x[0]", "x[1]", "x[2]", "x[3]", "z"], dtype="S"),
     )
     assert_equals(
         sample.get_vector("static_var_lower_bounds"), [0.0, 0.0, 0.0, 0.0, 0.0]
@@ -126,16 +126,16 @@ def test_constraint_getindex() -> None:
         senses=["=", "<", ">"],
         lhs=[
             [
-                ("x1", 1.0),
+                (b"x1", 1.0),
-                ("x2", 1.0),
+                (b"x2", 1.0),
             ],
             [
-                ("x2", 2.0),
+                (b"x2", 2.0),
-                ("x3", 2.0),
+                (b"x3", 2.0),
             ],
             [
-                ("x3", 3.0),
+                (b"x3", 3.0),
-                ("x4", 3.0),
+                (b"x4", 3.0),
             ],
         ],
     )
@@ -147,12 +147,12 @@ def test_constraint_getindex() -> None:
             senses=["=", ">"],
             lhs=[
                 [
-                    ("x1", 1.0),
+                    (b"x1", 1.0),
-                    ("x2", 1.0),
+                    (b"x2", 1.0),
                 ],
                 [
-                    ("x3", 3.0),
+                    (b"x3", 3.0),
-                    ("x4", 3.0),
+                    (b"x4", 3.0),
                 ],
             ],
         ),