add nrValues method

gtsam/discrete/DecisionTreeFactor.h

@@ -255,6 +255,12 @@ namespace gtsam {
      */
     DecisionTreeFactor prune(size_t maxNrAssignments) const;
 
+    /**
+     * Get the number of non-zero values contained in this factor.
+     * It could be much smaller than `prod_{key}(cardinality(key))`.
+     */
+    uint64_t nrValues() const override { return nrLeaves(); }
+
     /// @}
     /// @name Wrapper support
     /// @{

gtsam/discrete/DiscreteFactor.h

@@ -113,6 +113,12 @@ class GTSAM_EXPORT DiscreteFactor : public Factor {
 
   virtual DecisionTreeFactor toDecisionTreeFactor() const = 0;
 
+  /**
+   * Get the number of non-zero values contained in this factor.
+   * It could be much smaller than `prod_{key}(cardinality(key))`.
+   */
+  virtual uint64_t nrValues() const = 0;
+
   /// @}
   /// @name Wrapper support
   /// @{

gtsam/discrete/TableFactor.h

@@ -324,6 +324,12 @@ class GTSAM_EXPORT TableFactor : public DiscreteFactor {
    */
   TableFactor prune(size_t maxNrAssignments) const;
 
+  /**
+   * Get the number of non-zero values contained in this factor.
+   * It could be much smaller than `prod_{key}(cardinality(key))`.
+   */
+  uint64_t nrValues() const override { return sparse_table_.nonZeros(); }
+
   /// @}
   /// @name Wrapper support
   /// @{

gtsam_unstable/discrete/AllDiff.h

@@ -72,6 +72,9 @@ class GTSAM_UNSTABLE_EXPORT AllDiff : public Constraint {
   /// Partially apply known values, domain version
   Constraint::shared_ptr partiallyApply(
       const Domains&) const override;
+
+  /// Get the number of non-zero values contained in this factor.
+  uint64_t nrValues() const override { return 1; };
 };
 
 }  // namespace gtsam

gtsam_unstable/discrete/BinaryAllDiff.h

@@ -96,6 +96,9 @@ class BinaryAllDiff : public Constraint {
   AlgebraicDecisionTree<Key> errorTree() const override {
     throw std::runtime_error("BinaryAllDiff::error not implemented");
   }
+
+  /// Get the number of non-zero values contained in this factor.
+  uint64_t nrValues() const override { return 1; };
 };
 
 }  // namespace gtsam

gtsam_unstable/discrete/Domain.h

@@ -49,7 +49,7 @@ class GTSAM_UNSTABLE_EXPORT Domain : public Constraint {
   /// Erase a value, non const :-(
   void erase(size_t value) { values_.erase(value); }
 
-  size_t nrValues() const { return values_.size(); }
+  uint64_t nrValues() const override { return values_.size(); }
 
   bool isSingleton() const { return nrValues() == 1; }
 

gtsam_unstable/discrete/SingleValue.h

@@ -77,6 +77,9 @@ class GTSAM_UNSTABLE_EXPORT SingleValue : public Constraint {
   /// Partially apply known values, domain version
   Constraint::shared_ptr partiallyApply(
       const Domains& domains) const override;
+
+  /// Get the number of non-zero values contained in this factor.
+  uint64_t nrValues() const override { return 1; };
 };
 
 }  // namespace gtsam