Merge pull request #1785 from borglab/discrete-improv-2

gtsam/discrete/DiscreteConditional.cpp

@@ -236,6 +236,9 @@ DecisionTreeFactor::shared_ptr DiscreteConditional::likelihood(
 
 /* ************************************************************************** */
 size_t DiscreteConditional::argmax(const DiscreteValues& parentsValues) const {
+  ADT pFS = choose(parentsValues, true);  // P(F|S=parentsValues)
+
+  // Initialize
   size_t maxValue = 0;
   double maxP = 0;
   DiscreteValues values = parentsValues;
@@ -254,6 +257,33 @@ size_t DiscreteConditional::argmax(const DiscreteValues& parentsValues) const {
   return maxValue;
 }
 
+/* ************************************************************************** */
+void DiscreteConditional::argmaxInPlace(DiscreteValues* values) const {
+  ADT pFS = choose(*values, true);  // P(F|S=parentsValues)
+
+  // Initialize
+  DiscreteValues mpe;
+  double maxP = 0;
+
+  // Get all Possible Configurations
+  const auto allPosbValues = frontalAssignments();
+
+  // Find the maximum
+  for (const auto& frontalVals : allPosbValues) {
+    double pValueS = pFS(frontalVals);  // P(F=value|S=parentsValues)
+    // Update maximum solution if better
+    if (pValueS > maxP) {
+      maxP = pValueS;
+      mpe = frontalVals;
+    }
+  }
+
+  // set values (inPlace) to maximum
+  for (Key j : frontals()) {
+    (*values)[j] = mpe[j];
+  }
+}
+
 /* ************************************************************************** */
 void DiscreteConditional::sampleInPlace(DiscreteValues* values) const {
   assert(nrFrontals() == 1);

gtsam/discrete/DiscreteConditional.h

@@ -18,9 +18,9 @@
 
 #pragma once
 
-#include <gtsam/inference/Conditional-inst.h>
 #include <gtsam/discrete/DecisionTreeFactor.h>
 #include <gtsam/discrete/Signature.h>
+#include <gtsam/inference/Conditional-inst.h>
 
 #include <memory>
 #include <string>
@@ -159,9 +159,7 @@ class GTSAM_EXPORT DiscreteConditional
   /// @{
 
   /// Log-probability is just -error(x).
-  double logProbability(const DiscreteValues& x) const  {
+  double logProbability(const DiscreteValues& x) const { return -error(x); }
-    return -error(x);
-  }
 
   /// print index signature only
   void printSignature(
@@ -214,11 +212,18 @@ class GTSAM_EXPORT DiscreteConditional
   size_t sample() const;
 
   /**
-   * @brief Return assignment that maximizes distribution.
+   * @brief Return assignment for single frontal variable that maximizes value.
-   * @return Optimal assignment (1 frontal variable).
+   * @param parentsValues Known assignments for the parents.
+   * @return maximizing assignment for the frontal variable.
    */
   size_t argmax(const DiscreteValues& parentsValues = DiscreteValues()) const;
 
+  /**
+   * @brief Calculate assignment for frontal variables that maximizes value.
+   * @param (in/out) parentsValues Known assignments for the parents.
+   */
+  void argmaxInPlace(DiscreteValues* parentsValues) const;
+
   /// @}
   /// @name Advanced Interface
   /// @{
@@ -244,7 +249,6 @@ class GTSAM_EXPORT DiscreteConditional
   std::string html(const KeyFormatter& keyFormatter = DefaultKeyFormatter,
                    const Names& names = {}) const override;
 
-
   /// @}
   /// @name HybridValues methods.
   /// @{

gtsam/discrete/DiscreteLookupDAG.cpp

@@ -119,7 +119,8 @@ DiscreteLookupDAG DiscreteLookupDAG::FromBayesNet(
 
 DiscreteValues DiscreteLookupDAG::argmax(DiscreteValues result) const {
   // Argmax each node in turn in topological sort order (parents first).
-  for (auto it = std::make_reverse_iterator(end()); it != std::make_reverse_iterator(begin()); ++it) {
+  for (auto it = std::make_reverse_iterator(end());
+       it != std::make_reverse_iterator(begin()); ++it) {
     // dereference to get the sharedFactor to the lookup table
     (*it)->argmaxInPlace(&result);
   }