Allow negating activation variables (#116)

opvious/modeling/fragments.py

@@ -220,12 +220,12 @@ def wrapper(fn):
 class ActivationVariable(ModelFragment):
     """Indicator variable activation fragment
 
-    This variable tracks an underlying non-negative tensor. Assuming both of
-    its bounds are defined (see below) it will bel equal to 1 iff the
-    underlying tensor is positive and 0 otherwise.
+    This variable tracks an underlying tensor or tensor-like expression.
+    Assuming both of its bounds are defined (see below) it will be equal to 1
+    iff the underlying tensor is positive and 0 otherwise.
 
     Args:
-        tensor: Non-negative tensor-like
+        tensor: Tensor-like
         quantifiables: Tensor quantifiables, can be omitted if the tensor is a
             variable or parameter
         upper_bound: Value of the upper bound used in the activation
@@ -235,6 +235,7 @@ class ActivationVariable(ModelFragment):
             constraint. If `True` the variable's image's lower bound will be
             used, if `False` no deactivation constraint will be added.
         name: Name of the generated activation variable
+        negate: Negate the returned indicator variable.
         projection: Mask used to project the variable's quantification. When
             this is set, the indicator variable will be set to 1 iff at least
             one of the projected tensor values is positive.
@@ -249,6 +250,7 @@ def __new__(
         upper_bound: Union[ExpressionLike, TensorLike, bool] = True,
         lower_bound: Union[ExpressionLike, TensorLike, bool] = False,
         name: Optional[Name] = None,
+        negate=False,
         projection: Projection = -1,
     ) -> ActivationVariable:
         if not quantifiables and isinstance(tensor, Tensor):
@@ -282,7 +284,8 @@ def activates(self):
                         bound = bound(*cp.lifted)
                     elif bound is True:
                         bound = tensor_image().upper_bound
-                    yield bound * self.value(*cp) >= tensor(*cp.lifted)
+                    value = 1 - self.value(*cp) if negate else self.value(*cp)
+                    yield bound * value >= tensor(*cp.lifted)
 
             @constraint(disabled=lower_bound is False)
             def deactivates(self):
@@ -299,7 +302,8 @@ def deactivates(self):
                         bound = bound(*cp)
                     elif bound is True:
                         bound = tensor_image().lower_bound
-                    yield bound * self.value(*cp) <= term
+                    value = 1 - self.value(*cp) if negate else self.value(*cp)
+                    yield bound * value <= term
 
         return _Fragment()
 
@@ -338,3 +342,32 @@ def __call__(self, *subs: ExpressionLike) -> Expression:
 
 
 ActivationIndicator = ActivationVariable  # Deprecated alias
+
+
+@method_decorator(require_call=True)
+def activation_variable(
+    *quantifiables: Quantifiable,
+    upper_bound: Union[ExpressionLike, TensorLike, bool] = True,
+    lower_bound: Union[ExpressionLike, TensorLike, bool] = False,
+    name: Optional[Name] = None,
+    negate=False,
+    projection: Projection = -1,
+) -> Callable[[Callable[..., TensorLike]], ActivationVariable]:
+    """Transforms a method into an :class:`ActivationVariable` fragment
+
+    Note that this method may alter the underlying method's call signature if a
+    projection is specified.
+    """
+
+    def wrapper(fn):
+        return ActivationVariable(
+            fn,
+            *quantifiables,
+            lower_bound=lower_bound,
+            upper_bound=upper_bound,
+            name=name,
+            negate=negate,
+            projection=projection,
+        )
+
+    return wrapper

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "poetry.core.masonry.api"
 
 [tool.poetry]
 name = "opvious"
-version = "0.18.2rc1"
+version = "0.18.2rc2"
 description = "Opvious Python SDK"
 authors = ["Opvious Engineering <[email protected]>"]
 readme = "README.md"

tests/test_modeling.py

@@ -225,6 +225,68 @@ def all_covered(self):
             yield count >= 1
 
 
+class JobShopScheduling(om.Model):
+    tasks = om.Dimension()
+    duration = om.Parameter.natural(tasks)
+    machine = om.Parameter.natural(tasks)
+    dependency = om.Parameter.indicator(
+        (tasks, tasks), qualifiers=["child", "parent"]
+    )
+    task_start = om.Variable.natural(tasks)
+    horizon = om.Variable.natural()
+
+    @property
+    def competing_tasks(self):
+        for t1, t2 in self.tasks * self.tasks:
+            if t1 != t2 and self.machine(t1) == self.machine(t2):
+                yield t1, t2
+
+    def task_end(self, t):
+        return self.task_start(t) + self.duration(t)
+
+    @om.constraint
+    def all_tasks_end_within_horizon(self):
+        for t in self.tasks:
+            yield self.task_end(t) <= self.horizon()
+
+    @om.constraint
+    def child_starts_after_parent_ends(self):
+        for c, p in self.tasks * self.tasks:
+            if self.dependency(c, p):
+                yield self.task_start(c) >= self.task_end(p)
+
+    @om.fragments.activation_variable(
+        lambda init, self: init(
+            self.competing_tasks,
+            negate=True,
+            upper_bound=self.duration.total(),
+        )
+    )
+    def must_start_after(self, t1, t2):
+        return self.task_end(t2) - self.task_start(t1)
+
+    @om.fragments.activation_variable(
+        lambda init, self: init(
+            self.competing_tasks,
+            negate=True,
+            upper_bound=self.duration.total(),
+        )
+    )
+    def must_end_before(self, t1, t2):
+        return self.task_end(t1) - self.task_start(t2)
+
+    @om.constraint
+    def one_active_task_per_machine(self):
+        for t1, t2 in self.competing_tasks:
+            yield self.must_end_before(t1, t2) + self.must_start_after(
+                t1, t2
+            ) >= 1
+
+    @om.objective
+    def minimize_horizon(self):
+        return self.horizon()
+
+
 @pytest.mark.skipif(
     not client.authenticated, reason="No access token detected"
 )
@@ -235,6 +297,7 @@ class TestModeling:
         GroupExpenses(),
         Sudoku(),
         BinPacking(),
+        JobShopScheduling(),
     ]
 
     @pytest.mark.asyncio