Refactor Tests

cooper/__init__.py

@@ -1,11 +1,6 @@
 """Top-level package for Cooper."""
 
-import sys
-
-if sys.version_info >= (3, 8):
-    from importlib.metadata import PackageNotFoundError, version
-else:
-    from importlib_metadata import PackageNotFoundError, version
+from importlib.metadata import PackageNotFoundError, version
 
 try:
     __version__ = version("cooper")

cooper/cmp.py

@@ -113,6 +113,14 @@ def observed_strict_violations(self):
         for constraint_state in self.observed_constraints.values():
             yield constraint_state.strict_violation
 
+    def observed_constraint_features(self):
+        for constraint_state in self.observed_constraints.values():
+            yield constraint_state.constraint_features
+
+    def observed_strict_constraint_features(self):
+        for constraint_state in self.observed_constraints.values():
+            yield constraint_state.strict_constraint_features
+
 
 class ConstrainedMinimizationProblem(abc.ABC):
     """Template for constrained minimization problems."""
@@ -177,7 +185,7 @@ def named_penalty_coefficients(self) -> Iterator[tuple[str, PenaltyCoefficient]]
             if constraint.penalty_coefficient is not None:
                 yield constraint_name, constraint.penalty_coefficient
 
-    def dual_parameters(self) -> Iterator[Multiplier]:
+    def dual_parameters(self) -> Iterator[torch.nn.Parameter]:
         """Return an iterator over the parameters of the multipliers associated with the
         registered constraints of the CMP. This method is useful for instantiating the
         dual optimizers. If a multiplier is shared by several constraints, we only

cooper/constraints/constraint.py

@@ -1,7 +1,5 @@
 from typing import Literal, Optional, Type
 
-import torch
-
 from cooper.constraints.constraint_state import ConstraintState
 from cooper.constraints.constraint_type import ConstraintType
 from cooper.formulations import ContributionStore, Formulation, LagrangianFormulation
@@ -26,25 +24,16 @@ def __init__(
         self.formulation = formulation_type(constraint_type=self.constraint_type)
 
         self.multiplier = multiplier
-        if multiplier.constraint_type != self.constraint_type:
-            raise ValueError(
-                f"Attempted to pair {self.constraint_type} constraint, with {multiplier.constraint_type} multiplier."
-            )
-        self.multiplier.sanity_check()
+        self.multiplier.set_constraint_type(constraint_type)
 
         self.penalty_coefficient = penalty_coefficient
         self.sanity_check_penalty_coefficient()
 
     def sanity_check_penalty_coefficient(self) -> None:
-        if self.formulation.expects_penalty_coefficient:
-            if self.penalty_coefficient is None:
-                raise ValueError(f"{self.formulation_type} expects a penalty coefficient but none was provided.")
-            else:
-                if torch.any(self.penalty_coefficient.value < 0):
-                    raise ValueError("All entries of the penalty coefficient must be non-negative.")
-        else:
-            if self.penalty_coefficient is not None:
-                raise ValueError(f"Received unexpected penalty coefficient for {self.formulation_type}.")
+        if self.formulation.expects_penalty_coefficient and self.penalty_coefficient is None:
+            raise ValueError(f"{self.formulation_type} expects a penalty coefficient but none was provided.")
+        if not self.formulation.expects_penalty_coefficient and self.penalty_coefficient is not None:
+            raise ValueError(f"Received unexpected penalty coefficient for {self.formulation_type}.")
 
     def compute_contribution_to_lagrangian(
         self, constraint_state: ConstraintState, primal_or_dual: Literal["primal", "dual"]

cooper/constraints/constraint_state.py

@@ -51,9 +51,6 @@ class ConstraintState:
     contributes_to_dual_update: bool = True
 
     def __post_init__(self):
-        if self.constraint_features is not None and self.violation is None:
-            raise ValueError("violation must be provided if constraint_features is provided.")
-
         if self.strict_constraint_features is not None and self.strict_violation is None:
             raise ValueError("strict_violation must be provided if strict_constraint_features is provided.")
 
@@ -73,9 +70,9 @@ def extract_violations(self, do_unsqueeze=True) -> tuple[torch.Tensor, torch.Ten
         if do_unsqueeze:
             # If the violation is a scalar, we unsqueeze it to ensure that it has at
             # least one dimension for using einsum.
-            if len(violation.shape) == 0:
+            if violation.dim() == 0:
                 violation = violation.unsqueeze(0)
-            if len(strict_violation.shape) == 0:
+            if strict_violation.dim() == 0:
                 strict_violation = strict_violation.unsqueeze(0)
 
         return violation, strict_violation

cooper/formulations/formulations.py

@@ -42,6 +42,8 @@ def _prepare_kwargs_for_lagrangian_contribution(
 
         if self.expects_penalty_coefficient and penalty_coefficient is None:
             raise ValueError(f"{type(self).__name__} expects a penalty coefficient but none was provided.")
+        if not self.expects_penalty_coefficient and penalty_coefficient is not None:
+            raise ValueError(f"{type(self).__name__} does not expect a penalty coefficient but one was provided.")
 
         violation, strict_violation = constraint_state.extract_violations()
         constraint_features, strict_constraint_features = constraint_state.extract_constraint_features()

cooper/formulations/utils.py

@@ -8,21 +8,24 @@
 
 
 def evaluate_constraint_factor(
-    module: Union[Multiplier, PenaltyCoefficient], constraint_features: torch.Tensor, expand_shape: torch.Tensor
+    module: Union[Multiplier, PenaltyCoefficient],
+    constraint_features: Optional[torch.Tensor],
+    expand_shape: tuple[int, ...],
 ) -> torch.Tensor:
     """Evaluate the Lagrange multiplier or penalty coefficient associated with a
     constraint.
 
     Args:
         module: Multiplier or penalty coefficient module.
-        constraint_state: The current state of the constraint.
+        constraint_features: The observed features of the constraint.
+        expand_shape: Shape of the constraint violation tensor.
     """
 
     # TODO(gallego-posada): This way of calling the modules assumes either 0 or 1
     # arguments. This should be generalized to allow for multiple arguments.
-    value = module() if constraint_features is None else module(constraint_features)
+    value = module(constraint_features) if module.expects_constraint_features else module()
 
-    if len(value.shape) == 0:
+    if value.dim() == 0:
         # Unsqueeze value to make it a 1D tensor for consistent use in Formulations' einsum  calls
         value.unsqueeze_(0)
 
@@ -155,5 +158,3 @@ def compute_primal_quadratic_augmented_contribution(
         linear_term = compute_primal_weighted_violation(multiplier_value, violation)
         quadratic_penalty = compute_quadratic_penalty(penalty_coefficient_value, violation, constraint_type)
         return linear_term + quadratic_penalty
-    else:
-        raise ValueError(f"{constraint_type} is incompatible with quadratic penalties.")

cooper/multipliers/multipliers.py

@@ -9,6 +9,9 @@
 
 
 class Multiplier(torch.nn.Module, abc.ABC):
+    expects_constraint_features: bool
+    constraint_type: ConstraintType
+
     @abc.abstractmethod
     def forward(self, *args, **kwargs):
         """Return the current value of the multiplier."""
@@ -27,6 +30,10 @@ def sanity_check(self):
         # TODO(gallego-posada): Add docstring
         pass
 
+    def set_constraint_type(self, constraint_type):
+        self.constraint_type = constraint_type
+        self.sanity_check()
+
 
 class ExplicitMultiplier(Multiplier):
     """
@@ -46,23 +53,15 @@ class ExplicitMultiplier(Multiplier):
 
     def __init__(
         self,
-        constraint_type: ConstraintType,
         num_constraints: Optional[int] = None,
         init: Optional[torch.Tensor] = None,
         device: Optional[torch.device] = None,
         dtype: torch.dtype = torch.float32,
     ):
         super().__init__()
 
-        self.constraint_type = constraint_type
         self.weight = self.initialize_weight(num_constraints=num_constraints, init=init, device=device, dtype=dtype)
 
-        self.sanity_check()
-
-    @property
-    def is_inequality(self):
-        return self.constraint_type == ConstraintType.INEQUALITY
-
     def initialize_weight(
         self,
         num_constraints: Optional[int],
@@ -90,7 +89,7 @@ def device(self):
         return self.weight.device
 
     def sanity_check(self):
-        if self.is_inequality and torch.any(self.weight.data < 0):
+        if self.constraint_type == ConstraintType.INEQUALITY and torch.any(self.weight.data < 0):
             raise ValueError("For inequality constraint, all entries in multiplier must be non-negative.")
 
     @torch.no_grad()
@@ -100,12 +99,12 @@ def post_step_(self):
         the dual optimizer, and ensures that (if required) the multipliers are
         non-negative.
         """
-        if self.is_inequality:
+        if self.constraint_type == ConstraintType.INEQUALITY:
             # Ensures non-negativity for multipliers associated with inequality constraints.
             self.weight.data = torch.relu(self.weight.data)
 
     def __repr__(self):
-        return f"{type(self).__name__}(constraint_type={self.constraint_type}, num_constraints={self.weight.shape[0]})"
+        return f"{type(self).__name__}(num_constraints={self.weight.shape[0]})"
 
 
 class DenseMultiplier(ExplicitMultiplier):
@@ -120,6 +119,8 @@ class DenseMultiplier(ExplicitMultiplier):
     :py:class:`~cooper.multipliers.IndexedMultiplier`.
     """
 
+    expects_constraint_features = False
+
     def forward(self):
         """Return the current value of the multiplier."""
         return torch.clone(self.weight)
@@ -139,8 +140,10 @@ class IndexedMultiplier(ExplicitMultiplier):
     and memory-efficient sparse gradients (on GPU).
     """
 
-    def __init__(self, *args, **kwargs):
-        super(IndexedMultiplier, self).__init__(*args, **kwargs)
+    expects_constraint_features = True
+
+    def __init__(self, num_constraints=None, init=None, device=None, dtype=torch.float32):
+        super().__init__(num_constraints, init, device, dtype)
         if self.weight.dim() == 1:
             # To use the forward call in F.embedding, we must reshape the weight to be a
             # 2-dim tensor

cooper/multipliers/penalty_coefficients.py

@@ -1,5 +1,4 @@
 import abc
-import warnings
 from typing import Optional
 
 import torch
@@ -12,12 +11,13 @@ class PenaltyCoefficient(abc.ABC):
         init: Value of the penalty coefficient.
     """
 
+    expects_constraint_features: bool
+    _value: Optional[torch.Tensor] = None
+
     def __init__(self, init: torch.Tensor):
-        if init.requires_grad:
-            raise ValueError("PenaltyCoefficient should not require gradients.")
         if init.dim() > 1:
             raise ValueError("init must either be a scalar or a 1D tensor of shape `(num_constraints,)`.")
-        self._value = init.clone()
+        self.value = init
 
     @property
     def value(self):
@@ -28,16 +28,17 @@ def value(self):
     def value(self, value: torch.Tensor):
         """Update the value of the penalty."""
         if value.requires_grad:
-            raise ValueError("New value of PenaltyCoefficient should not require gradients.")
-        if value.shape != self._value.shape:
-            warnings.warn(
+            raise ValueError("PenaltyCoefficient should not require gradients.")
+        if self._value is not None and value.shape != self._value.shape:
+            raise ValueError(
                 f"New shape {value.shape} of PenaltyCoefficient does not match existing shape {self._value.shape}."
             )
         self._value = value.clone()
+        self.sanity_check()
 
     def to(self, device: Optional[torch.device] = None, dtype: Optional[torch.dtype] = None):
         """Move the penalty to a new device and/or change its dtype."""
-        self.value = self.value.to(device=device, dtype=dtype)
+        self._value = self._value.to(device=device, dtype=dtype)
         return self
 
     def state_dict(self):
@@ -46,6 +47,10 @@ def state_dict(self):
     def load_state_dict(self, state_dict):
         self._value = state_dict["value"]
 
+    def sanity_check(self):
+        if torch.any(self._value < 0):
+            raise ValueError("All entries of the penalty coefficient must be non-negative.")
+
     def __repr__(self):
         if self.value.numel() <= 10:
             return f"{type(self).__name__}({self.value})"
@@ -61,6 +66,8 @@ def __call__(self, *args, **kwargs):
 class DensePenaltyCoefficient(PenaltyCoefficient):
     """Constant (non-trainable) coefficient class used for Augmented Lagrangian formulation."""
 
+    expects_constraint_features = False
+
     @torch.no_grad()
     def __call__(self):
         """Return the current value of the penalty coefficient."""
@@ -73,6 +80,8 @@ class IndexedPenaltyCoefficient(PenaltyCoefficient):
     value of the penalty for a subset of constraints.
     """
 
+    expects_constraint_features = True
+
     @torch.no_grad()
     def __call__(self, indices: torch.Tensor):
         """Return the current value of the penalty coefficient at the provided indices.
@@ -86,6 +95,9 @@ def __call__(self, indices: torch.Tensor):
             # torch.nn.functional.embedding and *not* as masks.
             raise ValueError("Indices must be of type torch.long.")
 
+        if self.value.dim() == 0:
+            return self.value.clone()
+
         coefficient_values = torch.nn.functional.embedding(indices, self.value.unsqueeze(1), sparse=False)
 
         # Flatten coefficient values to 1D since Embedding works with 2D tensors.

cooper/optim/constrained_optimizers/constrained_optimizer.py

@@ -57,9 +57,9 @@ def base_sanity_checks(self):
         """
 
         if self.primal_optimizers is None:
-            raise RuntimeError("No primal optimizer(s) was provided for building a ConstrainedOptimizer.")
+            raise TypeError("No primal optimizer(s) was provided for building a ConstrainedOptimizer.")
         if self.dual_optimizers is None:
-            raise RuntimeError("No dual optimizer(s) was provided for building a ConstrainedOptimizer.")
+            raise TypeError("No dual optimizer(s) was provided for building a ConstrainedOptimizer.")
         for dual_optimizer in self.dual_optimizers:
             for param_group in dual_optimizer.param_groups:
                 if not param_group["maximize"]:

cooper/optim/constrained_optimizers/extrapolation_optimizer.py

@@ -39,9 +39,6 @@ def primal_extrapolation_step(self):
         """
         Perform an extrapolation step on the parameters associated with the primal variables.
         """
-        if not all(hasattr(primal_optimizer, "extrapolation") for primal_optimizer in self.primal_optimizers):
-            raise ValueError("All primal optimizers must implement an `extrapolation` method.")
-
         for primal_optimizer in self.primal_optimizers:
             primal_optimizer.extrapolation()
 
@@ -53,9 +50,6 @@ def dual_extrapolation_step(self):
         After being updated by the dual optimizer steps, the multipliers are
         post-processed (e.g. to ensure non-negativity for inequality constraints).
         """
-        if not all(hasattr(dual_optimizer, "extrapolation") for dual_optimizer in self.dual_optimizers):
-            raise ValueError("All dual optimizers must implement an `extrapolation` method.")
-
         # Update multipliers based on current constraint violations (gradients)
         # For unobserved constraints the gradient is None, so this is a no-op.
         for dual_optimizer in self.dual_optimizers:

cooper/optim/optimizer.py

@@ -29,7 +29,7 @@ def __init__(
         dual_optimizers: Optional[OneOrSequence[torch.optim.Optimizer]] = None,
     ):
         self.cmp = cmp
-        self.primal_optimizers = ensure_sequence(primal_optimizers)
+        self.primal_optimizers = ensure_sequence(primal_optimizers) if primal_optimizers is not None else None
         self.dual_optimizers = ensure_sequence(dual_optimizers) if dual_optimizers is not None else None
 
     def zero_grad(self):
@@ -38,11 +38,14 @@ def zero_grad(self):
         to zero. This includes both the primal and dual variables.
         """
         for primal_optimizer in self.primal_optimizers:
-            primal_optimizer.zero_grad()
+            # Prior to PyTorch 2.0, set_to_none=False was the default behavior.
+            # The default behavior was changed to set_to_none=True in PyTorch 2.0.
+            # We set set_to_none=True explicitly to ensure compatibility with both versions.
+            primal_optimizer.zero_grad(set_to_none=True)
 
         if self.dual_optimizers is not None:
             for dual_optimizer in self.dual_optimizers:
-                dual_optimizer.zero_grad()
+                dual_optimizer.zero_grad(set_to_none=True)
 
     @torch.no_grad()
     def primal_step(self):

cooper/penalty_coefficient_updaters/penalty_coefficient_updaters.py

@@ -72,7 +72,7 @@ def update_penalty_coefficient_(self, constraint: Constraint, constraint_state:
         # less than the tolerance, the penalty value is left unchanged.
         new_value = torch.where(condition, observed_penalty_values * self.growth_factor, observed_penalty_values)
 
-        if isinstance(penalty_coefficient, DensePenaltyCoefficient):
-            penalty_coefficient.value = new_value.detach()
-        elif isinstance(penalty_coefficient, IndexedPenaltyCoefficient):
+        if isinstance(penalty_coefficient, IndexedPenaltyCoefficient) and new_value.dim() > 0:
             penalty_coefficient.value[strict_constraint_features] = new_value.detach()
+        else:
+            penalty_coefficient.value = new_value.detach()

cooper/utils/utils.py

@@ -7,6 +7,4 @@ def ensure_sequence(argument: Any):
     Ensures that an argument is an instance of Sequence by wrapping it into a list
     whenever necessary. When argument is None, None is returned without wrapping.
     """
-    if argument is None:
-        return None
     return argument if isinstance(argument, Sequence) else [argument]