Merge pull request #1781 from borglab/discrete-improv

gtsam/discrete/DiscreteBayesNet.cpp

@@ -18,6 +18,8 @@
 
 #include <gtsam/discrete/DiscreteBayesNet.h>
 #include <gtsam/discrete/DiscreteConditional.h>
+#include <gtsam/discrete/DiscreteFactorGraph.h>
+#include <gtsam/discrete/DiscreteLookupDAG.h>
 #include <gtsam/inference/FactorGraph-inst.h>
 
 namespace gtsam {
@@ -56,7 +58,8 @@ DiscreteValues DiscreteBayesNet::sample() const {
 
 DiscreteValues DiscreteBayesNet::sample(DiscreteValues result) const {
   // sample 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) {
     (*it)->sampleInPlace(&result);
   }
   return result;

gtsam/discrete/DiscreteConditional.cpp

@@ -235,16 +235,19 @@ DecisionTreeFactor::shared_ptr DiscreteConditional::likelihood(
 }
 
 /* ************************************************************************** */
-size_t DiscreteConditional::argmax() const {
+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;
+
   assert(nrFrontals() == 1);
-  assert(nrParents() == 0);
-  DiscreteValues frontals;
   Key j = firstFrontalKey();
   for (size_t value = 0; value < cardinality(j); value++) {
-    frontals[j] = value;
-    double pValueS = (*this)(frontals);
+    values[j] = value;
+    double pValueS = (*this)(values);
     // Update MPE solution if better
     if (pValueS > maxP) {
       maxP = pValueS;
@@ -459,7 +462,7 @@ string DiscreteConditional::html(const KeyFormatter& keyFormatter,
 }
 
 /* ************************************************************************* */
-double DiscreteConditional::evaluate(const HybridValues& x) const{
+double DiscreteConditional::evaluate(const HybridValues& x) const {
   return this->evaluate(x.discrete());
 }
 /* ************************************************************************* */

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  {
-    return -error(x);
-  }
+  double logProbability(const DiscreteValues& x) const { return -error(x); }
 
   /// print index signature only
   void printSignature(
@@ -214,10 +212,11 @@ class GTSAM_EXPORT DiscreteConditional
   size_t sample() const;
 
   /**
-   * @brief Return assignment that maximizes distribution.
-   * @return Optimal assignment (1 frontal variable).
+   * @brief Return assignment for single frontal variable that maximizes value.
+   * @param parentsValues Known assignments for the parents.
+   * @return maximizing assignment for the frontal variable.
    */
-  size_t argmax() const;
+  size_t argmax(const DiscreteValues& parentsValues = DiscreteValues()) const;
 
   /// @}
   /// @name Advanced Interface
@@ -244,7 +243,6 @@ 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);
   }

gtsam/discrete/discrete.i

@@ -14,6 +14,9 @@ class DiscreteKeys {
   bool empty() const;
   gtsam::DiscreteKey at(size_t n) const;
   void push_back(const gtsam::DiscreteKey& point_pair);
+  void print(const std::string& s = "",
+             const gtsam::KeyFormatter& keyFormatter =
+                 gtsam::DefaultKeyFormatter) const;
 };
 
 // DiscreteValues is added in specializations/discrete.h as a std::map
@@ -104,6 +107,9 @@ virtual class DiscreteConditional : gtsam::DecisionTreeFactor {
   DiscreteConditional(const gtsam::DecisionTreeFactor& joint,
                       const gtsam::DecisionTreeFactor& marginal,
                       const gtsam::Ordering& orderedKeys);
+  DiscreteConditional(const gtsam::DiscreteKey& key,
+                      const gtsam::DiscreteKeys& parents,
+                      const std::vector<double>& table);
 
   // Standard interface
   double logNormalizationConstant() const;
@@ -131,6 +137,7 @@ virtual class DiscreteConditional : gtsam::DecisionTreeFactor {
   size_t sample(size_t value) const;
   size_t sample() const;
   void sampleInPlace(gtsam::DiscreteValues @parentsValues) const;
+  size_t argmax(const gtsam::DiscreteValues& parents) const;
 
   // Markdown and HTML
   string markdown(const gtsam::KeyFormatter& keyFormatter =
@@ -159,7 +166,6 @@ virtual class DiscreteDistribution : gtsam::DiscreteConditional {
                  gtsam::DefaultKeyFormatter) const;
   double operator()(size_t value) const;
   std::vector<double> pmf() const;
-  size_t argmax() const;
 };
 
 #include <gtsam/discrete/DiscreteBayesNet.h>

gtsam/discrete/tests/testDiscreteBayesNet.cpp

@@ -16,14 +16,13 @@
  *  @author Frank Dellaert
  */
 
+#include <CppUnitLite/TestHarness.h>
+#include <gtsam/base/Testable.h>
+#include <gtsam/base/Vector.h>
+#include <gtsam/base/debug.h>
 #include <gtsam/discrete/DiscreteBayesNet.h>
 #include <gtsam/discrete/DiscreteFactorGraph.h>
 #include <gtsam/discrete/DiscreteMarginals.h>
-#include <gtsam/base/debug.h>
-#include <gtsam/base/Testable.h>
-#include <gtsam/base/Vector.h>
-
-#include <CppUnitLite/TestHarness.h>
 
 #include <iostream>
 #include <string>
@@ -43,8 +42,7 @@ TEST(DiscreteBayesNet, bayesNet) {
   DiscreteKey Parent(0, 2), Child(1, 2);
 
   auto prior = std::make_shared<DiscreteConditional>(Parent % "6/4");
-  CHECK(assert_equal(ADT({Parent}, "0.6 0.4"),
-                     (ADT)*prior));
+  CHECK(assert_equal(ADT({Parent}, "0.6 0.4"), (ADT)*prior));
   bayesNet.push_back(prior);
 
   auto conditional =

gtsam/discrete/tests/testDiscreteConditional.cpp

@@ -289,6 +289,35 @@ TEST(DiscreteConditional, choose) {
   EXPECT(assert_equal(expected3, *actual3, 1e-9));
 }
 
+/* ************************************************************************* */
+// Check argmax on P(C|D) and P(D), plus tie-breaking for P(B)
+TEST(DiscreteConditional, Argmax) {
+  DiscreteKey B(2, 2), C(2, 2), D(4, 2);
+  DiscreteConditional B_prior(D, "1/1");
+  DiscreteConditional D_prior(D, "1/3");
+  DiscreteConditional C_given_D((C | D) = "1/4 1/1");
+
+  // Case 1: Tie breaking
+  size_t actual1 = B_prior.argmax();
+  // In the case of ties, the first value is chosen.
+  EXPECT_LONGS_EQUAL(0, actual1);
+  // Case 2: No parents
+  size_t actual2 = D_prior.argmax();
+  // Selects 1 since it has 0.75 probability
+  EXPECT_LONGS_EQUAL(1, actual2);
+
+  // Case 3: Given parent values
+  DiscreteValues given;
+  given[D.first] = 1;
+  size_t actual3 = C_given_D.argmax(given);
+  // Should be 0 since D=1 gives 0.5/0.5
+  EXPECT_LONGS_EQUAL(0, actual3);
+  
+  given[D.first] = 0;
+  size_t actual4 = C_given_D.argmax(given);
+  EXPECT_LONGS_EQUAL(1, actual4);
+}
+
 /* ************************************************************************* */
 // Check markdown representation looks as expected, no parents.
 TEST(DiscreteConditional, markdown_prior) {