From a27979e84ba4be26ec9754915477cb02d5df014a Mon Sep 17 00:00:00 2001
From: Varun Agrawal <varagrawal@gmail.com>
Date: Wed, 21 Dec 2022 20:20:56 +0530
Subject: [PATCH] minor refactoring

---
 gtsam/hybrid/HybridGaussianFactorGraph.cpp |  7 +++++--
 gtsam/hybrid/HybridGaussianFactorGraph.h   | 11 +++++------
 2 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/gtsam/hybrid/HybridGaussianFactorGraph.cpp b/gtsam/hybrid/HybridGaussianFactorGraph.cpp
index 39c3c2965..66beb3e4c 100644
--- a/gtsam/hybrid/HybridGaussianFactorGraph.cpp
+++ b/gtsam/hybrid/HybridGaussianFactorGraph.cpp
@@ -521,6 +521,7 @@ double HybridGaussianFactorGraph::probPrime(
     const VectorValues &continuousValues,
     const DiscreteValues &discreteValues) const {
   double error = this->error(continuousValues, discreteValues);
+  // NOTE: The 0.5 term is handled by each factor
   return std::exp(-error);
 }
 
@@ -528,8 +529,10 @@ double HybridGaussianFactorGraph::probPrime(
 AlgebraicDecisionTree<Key> HybridGaussianFactorGraph::probPrime(
     const VectorValues &continuousValues) const {
   AlgebraicDecisionTree<Key> error_tree = this->error(continuousValues);
-  AlgebraicDecisionTree<Key> prob_tree =
-      error_tree.apply([](double error) { return exp(-error); });
+  AlgebraicDecisionTree<Key> prob_tree = error_tree.apply([](double error) {
+    // NOTE: The 0.5 term is handled by each factor
+    return exp(-error);
+  });
   return prob_tree;
 }
 
diff --git a/gtsam/hybrid/HybridGaussianFactorGraph.h b/gtsam/hybrid/HybridGaussianFactorGraph.h
index b3bf8c0f5..02ebea74a 100644
--- a/gtsam/hybrid/HybridGaussianFactorGraph.h
+++ b/gtsam/hybrid/HybridGaussianFactorGraph.h
@@ -12,7 +12,7 @@
 /**
  * @file   HybridGaussianFactorGraph.h
  * @brief  Linearized Hybrid factor graph that uses type erasure
- * @author Fan Jiang
+ * @author Fan Jiang, Varun Agrawal
  * @date   Mar 11, 2022
  */
 
@@ -270,10 +270,9 @@ class GTSAM_EXPORT HybridGaussianFactorGraph
     const std::vector<DiscreteValues> assignments =
         DiscreteValues::CartesianProduct(discrete_keys);
 
-    // Save a copy of the original discrete key ordering
-    DiscreteKeys reversed_discrete_keys(discrete_keys);
-    // Reverse discrete keys order for correct tree construction
-    std::reverse(reversed_discrete_keys.begin(), reversed_discrete_keys.end());
+    // Get reversed discrete key ordering for correct tree construction
+    DiscreteKeys reversed_discrete_keys(discrete_keys.rbegin(),
+                                        discrete_keys.rend());
 
     // Create a decision tree of all the different VectorValues
     DecisionTree<Key, VectorValues::shared_ptr> delta_tree =
@@ -286,7 +285,7 @@ class GTSAM_EXPORT HybridGaussianFactorGraph
       VectorValues delta = *delta_tree(assignment);
 
       // If VectorValues is empty, it means this is a pruned branch.
-      // Set thr probPrime to 0.0.
+      // Set the probPrime to 0.0.
       if (delta.size() == 0) {
         probPrimes.push_back(0.0);
         continue;