Improved documentation, wrapper, and tests

gtsam/discrete/AlgebraicDecisionTree.h

@@ -28,9 +28,9 @@
 namespace gtsam {
 
   /**
-   * Algebraic Decision Trees fix the range to double
-   * Just has some nice constructors and some syntactic sugar
-   * TODO: consider eliminating this class altogether?
+   * An algebraic decision tree fixes the range of a DecisionTree to double.
+   * Just has some nice constructors and some syntactic sugar.
+   * TODO(dellaert): consider eliminating this class altogether?
    *
    * @ingroup discrete
    */
@@ -80,20 +80,62 @@ namespace gtsam {
     AlgebraicDecisionTree(const L& label, double y1, double y2)
         : Base(label, y1, y2) {}
 
-    /** Create a new leaf function splitting on a variable */
+    /**
+     * @brief Create a new leaf function splitting on a variable
+     *
+     * @param labelC: The label with cardinality 2
+     * @param y1: The value for the first key
+     * @param y2: The value for the second key
+     *
+     * Example:
+     * @code{.cpp}
+     * std::pair<string, size_t> A {"a", 2};
+     * AlgebraicDecisionTree<string> a(A, 0.6, 0.4);
+     * @endcode
+     */
     AlgebraicDecisionTree(const typename Base::LabelC& labelC, double y1,
                           double y2)
         : Base(labelC, y1, y2) {}
 
-    /** Create from keys and vector table */
+    /** 
+     * @brief Create from keys with cardinalities and a vector table
+     * 
+     * @param labelCs: The keys, with cardinalities, given as pairs
+     * @param ys: The vector table
+     *
+     * Example with three keys, A, B, and C, with cardinalities 2, 3, and 2,
+     * respectively, and a vector table of size 12:
+     * @code{.cpp}
+     * DiscreteKey A(0, 2), B(1, 3), C(2, 2);
+     * const vector<double> cpt{
+     *   1.0 / 3, 2.0 / 3, 3.0 / 7, 4.0 / 7, 5.0 / 11, 6.0 / 11,  //
+     *   1.0 / 9, 8.0 / 9, 3.0 / 6, 3.0 / 6, 5.0 / 10, 5.0 / 10};
+     * AlgebraicDecisionTree<Key> expected(A & B & C, cpt);
+     * @endcode
+     * The table is given in the following order:
+     *   A=0, B=0, C=0
+     *   A=0, B=0, C=1
+     *   ...
+     *   A=1, B=1, C=1
+     * Hence, the first line in the table is for A==0, and the second for A==1.
+     * In each line, the first two entries are for B==0, the next two for B==1,
+     * and the last two for B==2. Each pair is for a C value of 0 and 1.
+     */
     AlgebraicDecisionTree  //
         (const std::vector<typename Base::LabelC>& labelCs,
-        const std::vector<double>& ys) {
+         const std::vector<double>& ys) {
       this->root_ =
           Base::create(labelCs.begin(), labelCs.end(), ys.begin(), ys.end());
     }
 
-    /** Create from keys and string table */
+    /** 
+     * @brief Create from keys and string table
+     * 
+     * @param labelCs: The keys, with cardinalities, given as pairs
+     * @param table: The string table, given as a string of doubles.
+     * 
+     * @note Table needs to be in same order as the vector table in the other constructor.
+     */
     AlgebraicDecisionTree  //
         (const std::vector<typename Base::LabelC>& labelCs,
         const std::string& table) {
@@ -108,7 +150,13 @@ namespace gtsam {
           Base::create(labelCs.begin(), labelCs.end(), ys.begin(), ys.end());
     }
 
-    /** Create a new function splitting on a variable */
+    /** 
+     * @brief Create a range of decision trees, splitting on a single variable.
+     * 
+     * @param begin: Iterator to beginning of a range of decision trees
+     * @param end: Iterator to end of a range of decision trees
+     * @param label: The label to split on
+     */
     template <typename Iterator>
     AlgebraicDecisionTree(Iterator begin, Iterator end, const L& label)
         : Base(nullptr) {

gtsam/discrete/DecisionTree-inl.h

@@ -622,7 +622,7 @@ namespace gtsam {
   // B=1
   //  A=0: 3
   //  A=1: 4
-  // Note, through the magic of "compose", create([A B],[1 2 3 4]) will produce
+  // Note, through the magic of "compose", create([A B],[1 3 2 4]) will produce
   // exactly the same tree as above: the highest label is always the root.
   // However, it will be *way* faster if labels are given highest to lowest.
   template<typename L, typename Y>

gtsam/discrete/DecisionTree.h

@@ -37,9 +37,23 @@
 namespace gtsam {
 
   /**
-   * Decision Tree
-   * L = label for variables
-   * Y = function range (any algebra), e.g., bool, int, double
+   * @brief a decision tree is a function from assignments to values.
+   * @tparam L label for variables
+   * @tparam Y function range (any algebra), e.g., bool, int, double
+   * 
+   * After creating a decision tree on some variables, the tree can be evaluated
+   * on an assignment to those variables. Example:
+   * 
+   * @code{.cpp}
+   * // Create a decision stump one one variable 'a' with values 10 and 20.
+   * DecisionTree<char, int> tree('a', 10, 20);
+   * 
+   * // Evaluate the tree on an assignment to the variable.
+   * int value0 = tree({{'a', 0}}); // value0 = 10
+   * int value1 = tree({{'a', 1}}); // value1 = 20
+   * @endcode
+   * 
+   * More examples can be found in testDecisionTree.cpp
    *
    * @ingroup discrete
    */
@@ -132,7 +146,8 @@ namespace gtsam {
     NodePtr root_;
 
    protected:
-    /** Internal recursive function to create from keys, cardinalities, 
+    /** 
+     * Internal recursive function to create from keys, cardinalities, 
      * and Y values 
      */
     template<typename It, typename ValueIt>
@@ -163,7 +178,13 @@ namespace gtsam {
     /** Create a constant */
     explicit DecisionTree(const Y& y);
 
-    /// Create tree with 2 assignments `y1`, `y2`, splitting on variable `label`
+    /**
+     * @brief Create tree with 2 assignments `y1`, `y2`, splitting on variable `label`
+     * 
+     * @param label The variable to split on.
+     * @param y1 The value for the first assignment.
+     * @param y2 The value for the second assignment.
+     */
     DecisionTree(const L& label, const Y& y1, const Y& y2);
 
     /** Allow Label+Cardinality for convenience */

gtsam/discrete/DecisionTreeFactor.h

@@ -63,11 +63,46 @@ namespace gtsam {
     /** Constructor from DiscreteKeys and AlgebraicDecisionTree */
     DecisionTreeFactor(const DiscreteKeys& keys, const ADT& potentials);
 
-    /** Constructor from doubles */
+    /**
+     * @brief Constructor from doubles
+     *
+     * @param keys The discrete keys.
+     * @param table The table of values.
+     *
+     * @throw std::invalid_argument if the size of `table` does not match the
+     * number of assignments.
+     *
+     * Example:
+     * @code{.cpp}
+     * DiscreteKey X(0,2), Y(1,3);
+     * const std::vector<double> table {2, 5, 3, 6, 4, 7};
+     * DecisionTreeFactor f1({X, Y}, table);
+     * @endcode
+     *
+     * The values in the table should be laid out so that the first key varies
+     * the slowest, and the last key the fastest.
+     */
     DecisionTreeFactor(const DiscreteKeys& keys,
-                      const std::vector<double>& table);
+                       const std::vector<double>& table);
 
-    /** Constructor from string */
+    /**
+     * @brief Constructor from string
+     *
+     * @param keys The discrete keys.
+     * @param table The table of values.
+     *
+     * @throw std::invalid_argument if the size of `table` does not match the
+     * number of assignments.
+     *
+     * Example:
+     * @code{.cpp}
+     * DiscreteKey X(0,2), Y(1,3);
+     * DecisionTreeFactor factor({X, Y}, "2 5 3 6 4 7");
+     * @endcode
+     *
+     * The values in the table should be laid out so that the first key varies
+     * the slowest, and the last key the fastest.
+     */
     DecisionTreeFactor(const DiscreteKeys& keys, const std::string& table);
 
     /// Single-key specialization

gtsam/discrete/DiscreteBayesTree.h

@@ -59,6 +59,11 @@ class GTSAM_EXPORT DiscreteBayesTreeClique
 
   //** evaluate conditional probability of subtree for given DiscreteValues */
   double evaluate(const DiscreteValues& values) const;
+
+  //** (Preferred) sugar for the above for given DiscreteValues */
+  double operator()(const DiscreteValues& values) const {
+    return evaluate(values);
+  }
 };
 
 /* ************************************************************************* */

gtsam/discrete/DiscreteFactorGraph.h

@@ -42,16 +42,30 @@ class DiscreteJunctionTree;
 
 /**
  * @brief Main elimination function for DiscreteFactorGraph.
- * 
- * @param factors 
- * @param keys 
- * @return GTSAM_EXPORT
+ *
+ * @param factors The factor graph to eliminate.
+ * @param frontalKeys An ordering for which variables to eliminate.
+ * @return A pair of the resulting conditional and the separator factor.
  * @ingroup discrete
  */
-GTSAM_EXPORT std::pair<boost::shared_ptr<DiscreteConditional>, DecisionTreeFactor::shared_ptr>
-EliminateDiscrete(const DiscreteFactorGraph& factors, const Ordering& keys);
+GTSAM_EXPORT
+std::pair<DiscreteConditional::shared_ptr, DecisionTreeFactor::shared_ptr>
+EliminateDiscrete(const DiscreteFactorGraph& factors,
+                  const Ordering& frontalKeys);
+
+/**
+ * @brief Alternate elimination function for that creates non-normalized lookup tables.
+ *
+ * @param factors The factor graph to eliminate.
+ * @param frontalKeys An ordering for which variables to eliminate.
+ * @return A pair of the resulting lookup table and the separator factor.
+ * @ingroup discrete
+ */
+GTSAM_EXPORT
+std::pair<DiscreteConditional::shared_ptr, DecisionTreeFactor::shared_ptr>
+EliminateForMPE(const DiscreteFactorGraph& factors,
+                const Ordering& frontalKeys);
 
-/* ************************************************************************* */
 template<> struct EliminationTraits<DiscreteFactorGraph>
 {
   typedef DiscreteFactor FactorType;                   ///< Type of factors in factor graph
@@ -61,12 +75,14 @@ template<> struct EliminationTraits<DiscreteFactorGraph>
   typedef DiscreteEliminationTree EliminationTreeType; ///< Type of elimination tree
   typedef DiscreteBayesTree BayesTreeType;             ///< Type of Bayes tree
   typedef DiscreteJunctionTree JunctionTreeType;       ///< Type of Junction tree
+
   /// The default dense elimination function
   static std::pair<boost::shared_ptr<ConditionalType>,
                    boost::shared_ptr<FactorType> >
   DefaultEliminate(const FactorGraphType& factors, const Ordering& keys) {
     return EliminateDiscrete(factors, keys);
   }
+
   /// The default ordering generation function
   static Ordering DefaultOrderingFunc(
       const FactorGraphType& graph,
@@ -75,7 +91,6 @@ template<> struct EliminationTraits<DiscreteFactorGraph>
   }
 };
 
-/* ************************************************************************* */
 /**
  * A Discrete Factor Graph is a factor graph where all factors are Discrete, i.e.
  *   Factor == DiscreteFactor
@@ -109,8 +124,8 @@ class GTSAM_EXPORT DiscreteFactorGraph
 
   /** Implicit copy/downcast constructor to override explicit template container
    * constructor */
-  template <class DERIVEDFACTOR>
-  DiscreteFactorGraph(const FactorGraph<DERIVEDFACTOR>& graph) : Base(graph) {}
+  template <class DERIVED_FACTOR>
+  DiscreteFactorGraph(const FactorGraph<DERIVED_FACTOR>& graph) : Base(graph) {}
 
   /// Destructor
   virtual ~DiscreteFactorGraph() {}
@@ -231,10 +246,6 @@ class GTSAM_EXPORT DiscreteFactorGraph
   /// @}
 };  // \ DiscreteFactorGraph
 
-std::pair<DiscreteConditional::shared_ptr, DecisionTreeFactor::shared_ptr>  //
-EliminateForMPE(const DiscreteFactorGraph& factors,
-                const Ordering& frontalKeys);
-
 /// traits
 template <>
 struct traits<DiscreteFactorGraph> : public Testable<DiscreteFactorGraph> {};

gtsam/discrete/DiscreteJunctionTree.h

@@ -66,4 +66,6 @@ namespace gtsam {
     DiscreteJunctionTree(const DiscreteEliminationTree& eliminationTree);
   };
 
+  /// typedef for wrapper:
+  using DiscreteCluster = DiscreteJunctionTree::Cluster;
 }

gtsam/discrete/DiscreteValues.h

@@ -120,6 +120,11 @@ class GTSAM_EXPORT DiscreteValues : public Assignment<Key> {
   /// @}
 };
 
+/// Free version of CartesianProduct.
+inline std::vector<DiscreteValues> cartesianProduct(const DiscreteKeys& keys) {
+  return DiscreteValues::CartesianProduct(keys);
+}
+
 /// Free version of markdown.
 std::string markdown(const DiscreteValues& values,
                      const KeyFormatter& keyFormatter = DefaultKeyFormatter,