Add DisjointCover node

dwave/optimization/generators.py

@@ -34,6 +34,7 @@
     concatenate,
     exp,
     expit,
+    is_disjoint_cover,
     logical_or,
     maximum,
     minimum,
@@ -377,15 +378,16 @@ class as the decision variable being optimized, with permutations of its
         The :meth:`~dwave.optimization.model.Model.iter_decisions` method
         obtains the decision variables of the generated model.
 
-        >>> routes = next(model.iter_decisions())
+        >>> routes = list(model.iter_decisions())
 
         To test the solution above, set it in the model as the state of the
         decision variable. **Skip these next lines** if you have submitted your
         model to the `Leap <https://cloud.dwavesys.com/leap/>`_ :term:`hybrid`
         nonlinear :term:`solver`.
 
         >>> model.states.resize(1)
-        >>> routes.set_state(0, [[2., 7., 1., 5.], [4., 3., 8., 6., 0.]])
+        >>> routes[0].set_state(0, [2., 7., 1., 5.])
+        >>> routes[1].set_state(0, [4., 3., 8., 6., 0.])
 
         You can use the :meth:`~dwave.optimization.model.Model.iter_constraints`
         method to check feasibility of constructed or returned solutions. Here,
@@ -398,7 +400,7 @@ class as the decision variable being optimized, with permutations of its
         ...     for i in range(model.states.size()):
         ...         if capacity_constraint.state(i):    # Filter on feasibility
         ...             print((f"Objective value #{i} is {model.objective.state(i).round(2)} for routes\n"
-        ...                    f"    {[r.state(i).tolist() for r in routes.iter_successors()]}"))
+        ...                    f"    {[r.state(i).tolist() for r in routes]}"))
         Objective value #0 is 423.8 for routes
             [[2.0, 7.0, 1.0, 5.0], [4.0, 3.0, 8.0, 6.0, 0.0]]
     """
@@ -511,10 +513,8 @@ class as the decision variable being optimized, with permutations of its
     demand = model.constant(customer_demand)
     capacity = model.constant(vehicle_capacity)
 
-    # Add the decision variable
-    routes = model.disjoint_lists_symbol(
-        primary_set_size=num_customers,
-        num_disjoint_lists=number_of_vehicles)
+    routes = [model.list(num_customers, min_size=0) for _ in range(number_of_vehicles)]
+    model.add_constraint(is_disjoint_cover(routes))
 
     # The objective is to minimize the distance traveled.
     # This is calculated by adding the distance from the depot to the 1st customer
@@ -631,15 +631,16 @@ class as the decision variable being optimized, with permutations of its
         The :meth:`~dwave.optimization.model.Model.iter_decisions` method
         obtains the decision variables of the generated model.
 
-        >>> routes = next(model.iter_decisions())
+        >>> routes = list(model.iter_decisions())
 
         To test the solution above, set it in the model as the state of the
         decision variable. **Skip these next lines** if you have submitted your
         model to the `Leap <https://cloud.dwavesys.com/leap/>`_ :term:`hybrid`
         nonlinear :term:`solver`.
 
         >>> model.states.resize(1)
-        >>> routes.set_state(0, [[0, 2], [1]])
+        >>> routes[0].set_state(0, [0, 2])
+        >>> routes[1].set_state(0, [1])
 
         You can use the :meth:`~dwave.optimization.model.Model.iter_constraints`
         method to check feasibility of constructed or returned solutions. Here,
@@ -757,9 +758,8 @@ class as the decision variable being optimized, with permutations of its
     one = model.constant(1)
 
     # Add the decision variable
-    routes = model.disjoint_lists_symbol(
-        primary_set_size=num_customers,
-        num_disjoint_lists=number_of_vehicles)
+    routes = [model.list(num_customers, min_size=0) for _ in range(number_of_vehicles)]
+    model.add_constraint(is_disjoint_cover(routes))
 
     # Capacity constraint
     capacity_constraints = [(demand[routes[vehicle_idx]].sum() <= capacity)

dwave/optimization/include/dwave-optimization/nodes.hpp

@@ -28,5 +28,6 @@
 #include "dwave-optimization/nodes/numbers.hpp"
 #include "dwave-optimization/nodes/quadratic_model.hpp"
 #include "dwave-optimization/nodes/reduce.hpp"
+#include "dwave-optimization/nodes/set_routines.hpp"
 #include "dwave-optimization/nodes/testing.hpp"
 #include "dwave-optimization/nodes/unaryop.hpp"

dwave/optimization/include/dwave-optimization/nodes/set_routines.hpp

@@ -22,6 +22,45 @@
 
 namespace dwave::optimization {
 
+class IsDisjointCoverNode : public ScalarOutputMixin<ArrayNode, false> {
+ public:
+    IsDisjointCoverNode(std::span<ArrayNode*> node_ptrs, ssize_t primary_set_size);
+
+    /// @copydoc Array::buff()
+    double const* buff(const State& state) const override;
+
+    /// @copydoc Node::commit()
+    void commit(State& state) const override;
+
+    /// @copydoc Array::diff()
+    std::span<const Update> diff(const State& state) const override;
+
+    /// @copydoc Node::initialize_state()
+    void initialize_state(State& state) const override;
+
+    /// @copydoc Array::integral()
+    bool integral() const override;
+
+    /// @copydoc Array::max()
+    double max() const override;
+
+    /// @copydoc Array::min()
+    double min() const override;
+
+    /// The size of the primary set to be covered
+    ssize_t primary_set_size() const { return primary_set_size_; };
+
+    /// @copydoc Node::propagate()
+    void propagate(State& state) const override;
+
+    /// @copydoc Node::revert()
+    void revert(State& state) const override;
+
+ private:
+    ssize_t primary_set_size_;
+    std::vector<Array*> operands_;
+};
+
 class IsInNode : public ArrayOutputMixin<ArrayNode> {
  public:
     IsInNode(ArrayNode* element_ptr, ArrayNode* test_elements_ptr);

dwave/optimization/libcpp/nodes/set_routines.pxd

@@ -16,5 +16,8 @@ from dwave.optimization.libcpp.graph cimport ArrayNode
 
 
 cdef extern from "dwave-optimization/nodes/set_routines.hpp" namespace "dwave::optimization" nogil:
+    cdef cppclass IsDisjointCoverNode(ArrayNode):
+        Py_ssize_t primary_set_size() const
+
     cdef cppclass IsInNode(ArrayNode):
         pass

dwave/optimization/mathematical.py

@@ -38,6 +38,7 @@
     Exp,
     Expit,
     Extract,
+    IsDisjointCover,
     IsIn,
     LessEqual,
     LinearProgram,
@@ -95,6 +96,7 @@
     "expit",
     "extract",
     "hstack",
+    "is_disjoint_cover",
     "isin",
     "less_equal",
     "linprog",
@@ -1110,6 +1112,52 @@ def hstack(arrays: collections.abc.Sequence[ArraySymbol]) -> ArraySymbol:
         return concatenate(arrays, 1)
 
 
+def is_disjoint_cover(subsets: list[ArraySymbol], *, primary_set_size: int|None = None) -> IsDisjointCover:
+    """Return whether the symbols are disjoint, set-like, and cover a set of integers.
+
+    Determines whether a collection of array symbols is disjoint and the union equals a fixed set.
+
+    Args:
+        subsets: List of array symbols to test whether they are disjoint and cover the primary set
+        primary_set_size: Number of elements in the primary set: {0, 1, ..., primary_set_size - 1}.
+            Must be non-negative. If `None`, primary set size is inferred from the common, finite,
+            nonnegative maximum value of the arrays.
+
+    Returns:
+        A scalar boolean-valued array symbol indicating whether the subsets are a disjoint cover
+
+    Examples:
+        >>> from dwave.optimization.model import Model
+        >>> from dwave.optimization.mathematical import is_disjoint_cover
+        ...
+        >>> model = Model()
+        >>> model.states.resize(1)
+        >>> subsets = []
+        >>> subsets.append(model.constant([0, 1]))
+        >>> subsets.append(model.constant([2, 3, 4]))
+        >>> subsets.append(model.constant([]))
+        >>> is_disjoint = is_disjoint_cover(subsets, primary_set_size=5)
+        >>> with model.lock():
+        ...     print(is_disjoint.state(0))
+        1.0
+
+    See Also:
+        :class:`~dwave.optimization.symbols.IsDisjointCover`: Generated symbol
+
+        :func:`.isin`
+
+    .. versionadded:: 0.7.2
+    """
+    if primary_set_size is None:
+        primary_set_size = int(subsets[0].info().max) + 1
+        if not np.isfinite(primary_set_size) or primary_set_size <= 0:
+            raise ValueError("Cannot infer primary set size from subsets")
+        for subset in subsets[1:]:
+            if int(subset.info().max) != primary_set_size - 1:
+                raise ValueError("Cannot infer primary set size from subsets")
+    return IsDisjointCover(subsets, primary_set_size)
+
+
 def isin(element: ArraySymbol, test_elements: ArraySymbol) -> IsIn:
     """Return which values of one array symbol are in another.
 

dwave/optimization/model.py

@@ -591,6 +591,15 @@ def disjoint_lists_symbol(
 
             :meth:`.iter_decisions`, :meth:`.iter_successors`
         """
+        warnings.warn(
+            "The use of Model.disjoint_lists_symbol() is deprecated "
+            "since dwave.optimization 0.7.2. Use\n"
+            "from dwave.optimization.mathematical import is_disjoint_cover\n"
+            "lists = [model.list(primary_set_size, min_size=0) for _ in range(num_disjoint_lists)]\n"
+            "model.add_constraint(is_disjoint_cover(primary_set_size, lists))",
+            DeprecationWarning,
+        )
+
         from dwave.optimization.symbols import DisjointLists, DisjointList  # avoid circular import
         disjoint_lists = DisjointLists(self, primary_set_size, num_disjoint_lists)