update ComputeLeafOrdering to give a correct vector of values

Author: varunagrawal

gtsam/discrete/TableFactor.cpp

@@ -64,27 +64,69 @@ TableFactor::TableFactor(const DiscreteKeys& dkeys,
 /**
  * @brief Compute the correct ordering of the leaves in the decision tree.
  *
- * This is done by first taking all the values which have modulo 0 value with
- * the cardinality of the innermost key `n`, and we go up to modulo n.
- *
  * @param dt The DecisionTree
- * @return std::vector<double>
+ * @return Eigen::SparseVector<double>
  */
-std::vector<double> ComputeLeafOrdering(const DiscreteKeys& dkeys,
-                                        const DecisionTreeFactor& dt) {
-  std::vector<double> probs = dt.probabilities();
-  std::vector<double> ordered;
+static Eigen::SparseVector<double> ComputeLeafOrdering(
+    const DiscreteKeys& dkeys, const DecisionTreeFactor& dt) {
+  // SparseVector needs to know the maximum possible index,
+  // so we compute the product of cardinalities.
+  size_t prod_cardinality = 1;
+  for (auto&& [_, c] : dt.cardinalities()) {
+    prod_cardinality *= c;
+  }
+  Eigen::SparseVector<double> sparse_table(prod_cardinality);
+  size_t nrValues = 0;
+  dt.visit([&nrValues](double x) {
+    if (x > 0) nrValues += 1;
+  });
+  sparse_table.reserve(nrValues);
+
+  std::set<Key> allKeys(dt.keys().begin(), dt.keys().end());
+
+  auto op = [&](const Assignment<Key>& assignment, double p) {
+    if (p > 0) {
+      // Get all the keys involved in this assignment
+      std::set<Key> assignment_keys;
+      for (auto&& [k, _] : assignment) {
+        assignment_keys.insert(k);
+      }
 
-  size_t n = dkeys[0].second;
+      // Find the keys missing in the assignment
+      std::vector<Key> diff;
+      std::set_difference(allKeys.begin(), allKeys.end(),
+                          assignment_keys.begin(), assignment_keys.end(),
+                          std::back_inserter(diff));
 
-  for (size_t k = 0; k < n; ++k) {
-    for (size_t idx = 0; idx < probs.size(); ++idx) {
-      if (idx % n == k) {
-        ordered.push_back(probs[idx]);
+      // Generate all assignments using the missing keys
+      DiscreteKeys extras;
+      for (auto&& key : diff) {
+        extras.push_back({key, dt.cardinality(key)});
+      }
+      auto&& extra_assignments = DiscreteValues::CartesianProduct(extras);
+
+      for (auto&& extra : extra_assignments) {
+        // Create new assignment using the extra assignment
+        DiscreteValues updated_assignment(assignment);
+        updated_assignment.insert(extra);
+
+        // Generate index and add to the sparse vector.
+        Eigen::Index idx = 0;
+        size_t prev_cardinality = 1;
+        // We go in reverse since a DecisionTree has the highest label first
+        for (auto&& it = updated_assignment.rbegin();
+             it != updated_assignment.rend(); it++) {
+          idx += prev_cardinality * it->second;
+          prev_cardinality *= dt.cardinality(it->first);
+        }
+        sparse_table.coeffRef(idx) = p;
       }
     }
-  }
-  return ordered;
+  };
+
+  dt.visitWith(op);
+
+  return sparse_table;
 }
 
 /* ************************************************************************ */