New, more powerful choose, yields a Conditional now

gtsam/discrete/DiscreteConditional.cpp

@@ -150,60 +150,57 @@ void DiscreteConditional::print(const string& s,
 /* ******************************************************************************** */
 bool DiscreteConditional::equals(const DiscreteFactor& other,
                                  double tol) const {
-  if (!dynamic_cast<const DecisionTreeFactor*>(&other))
+  if (!dynamic_cast<const DecisionTreeFactor*>(&other)) {
     return false;
-  else {
-    const DecisionTreeFactor& f(
-        static_cast<const DecisionTreeFactor&>(other));
+  } else {
+    const DecisionTreeFactor& f(static_cast<const DecisionTreeFactor&>(other));
     return DecisionTreeFactor::equals(f, tol);
   }
 }
 
-/* ******************************************************************************** */
+/* ************************************************************************** */
 static DiscreteConditional::ADT Choose(const DiscreteConditional& conditional,
-                                       const DiscreteValues& parentsValues) {
+                                       const DiscreteValues& given,
+                                       bool forceComplete = true) {
   // Get the big decision tree with all the levels, and then go down the
   // branches based on the value of the parent variables.
   DiscreteConditional::ADT adt(conditional);
   size_t value;
   for (Key j : conditional.parents()) {
     try {
-      value = parentsValues.at(j);
+      value = given.at(j);
       adt = adt.choose(j, value);  // ADT keeps getting smaller.
     } catch (std::out_of_range&) {
-      parentsValues.print("parentsValues: ");
-      throw runtime_error("DiscreteConditional::choose: parent value missing");
-    };
+      if (forceComplete) {
+        given.print("parentsValues: ");
+        throw runtime_error(
+            "DiscreteConditional::Choose: parent value missing");
+      }
+    }
   }
   return adt;
 }
 
-/* ******************************************************************************** */
-DecisionTreeFactor::shared_ptr DiscreteConditional::choose(
-    const DiscreteValues& parentsValues) const {
-  // Get the big decision tree with all the levels, and then go down the
-  // branches based on the value of the parent variables.
-  ADT adt(*this);
-  size_t value;
-  for (Key j : parents()) {
-    try {
-      value = parentsValues.at(j);
-      adt = adt.choose(j, value);  // ADT keeps getting smaller.
-    } catch (exception&) {
-      parentsValues.print("parentsValues: ");
-      throw runtime_error("DiscreteConditional::choose: parent value missing");
-    };
-  }
+/* ************************************************************************** */
+DiscreteConditional::shared_ptr DiscreteConditional::choose(
+    const DiscreteValues& given) const {
+  ADT adt = Choose(*this, given, false);  // P(F|S=given)
 
-  // Convert ADT to factor.
-  DiscreteKeys discreteKeys;
+  // Collect all keys not in given.
+  DiscreteKeys dKeys;
   for (Key j : frontals()) {
-    discreteKeys.emplace_back(j, this->cardinality(j));
+    dKeys.emplace_back(j, this->cardinality(j));
   }
-  return boost::make_shared<DecisionTreeFactor>(discreteKeys, adt);
+  for (size_t i = nrFrontals(); i < size(); i++) {
+    Key j = keys_[i];
+    if (given.count(j) == 0) {
+      dKeys.emplace_back(j, this->cardinality(j));
+    }
+  }
+  return boost::make_shared<DiscreteConditional>(nrFrontals(), dKeys, adt);
 }
 
-/* ******************************************************************************** */
+/* ************************************************************************** */
 DecisionTreeFactor::shared_ptr DiscreteConditional::likelihood(
     const DiscreteValues& frontalValues) const {
   // Get the big decision tree with all the levels, and then go down the
@@ -217,7 +214,7 @@ DecisionTreeFactor::shared_ptr DiscreteConditional::likelihood(
     } catch (exception&) {
       frontalValues.print("frontalValues: ");
       throw runtime_error("DiscreteConditional::choose: frontal value missing");
-    };
+    }
   }
 
   // Convert ADT to factor.
@@ -242,7 +239,6 @@ DecisionTreeFactor::shared_ptr DiscreteConditional::likelihood(
 
 /* ************************************************************************** */
 void DiscreteConditional::solveInPlace(DiscreteValues* values) const {
-  // TODO(Abhijit): is this really the fastest way? He thinks it is.
   ADT pFS = Choose(*this, *values);  // P(F|S=parentsValues)
 
   // Initialize
@@ -276,10 +272,8 @@ void DiscreteConditional::sampleInPlace(DiscreteValues* values) const {
   (*values)[j] = sampled; // store result in partial solution
 }
 
-/* ******************************************************************************** */
+/* ************************************************************************** */
 size_t DiscreteConditional::solve(const DiscreteValues& parentsValues) const {
-
-  // TODO: is this really the fastest way? I think it is.
   ADT pFS = Choose(*this, parentsValues);  // P(F|S=parentsValues)
 
   // Then, find the max over all remaining

gtsam/discrete/DiscreteConditional.h

@@ -157,9 +157,20 @@ class GTSAM_EXPORT DiscreteConditional
     return ADT::operator()(values);
   }
 
-  /** Restrict to given parent values, returns DecisionTreeFactor */
-  DecisionTreeFactor::shared_ptr choose(
-      const DiscreteValues& parentsValues) const;
+  /** 
+   * @brief restrict to given *parent* values.
+   * 
+   * Note: does not need be complete set. Examples:
+   * 
+   * P(C|D,E) + . -> P(C|D,E)
+   * P(C|D,E) + E -> P(C|D)
+   * P(C|D,E) + D -> P(C|E)
+   * P(C|D,E) + D,E -> P(C)
+   * P(C|D,E) + C -> error!
+   * 
+   * @return a shared_ptr to a new DiscreteConditional
+   */
+  shared_ptr choose(const DiscreteValues& given) const;
 
   /** Convert to a likelihood factor by providing value before bar. */
   DecisionTreeFactor::shared_ptr likelihood(

gtsam/discrete/discrete.i

@@ -107,8 +107,7 @@ virtual class DiscreteConditional : gtsam::DecisionTreeFactor {
   void printSignature(
       string s = "Discrete Conditional: ",
       const gtsam::KeyFormatter& formatter = gtsam::DefaultKeyFormatter) const;
-  gtsam::DecisionTreeFactor* choose(
-      const gtsam::DiscreteValues& parentsValues) const;
+  gtsam::DecisionTreeFactor* choose(const gtsam::DiscreteValues& given) const;
   gtsam::DecisionTreeFactor* likelihood(
       const gtsam::DiscreteValues& frontalValues) const;
   gtsam::DecisionTreeFactor* likelihood(size_t value) const;

gtsam/discrete/tests/testDiscreteConditional.cpp

@@ -221,6 +221,34 @@ TEST(DiscreteConditional, likelihood) {
   EXPECT(assert_equal(expected1, *actual1, 1e-9));
 }
 
+/* ************************************************************************* */
+// Check choose on P(C|D,E)
+TEST(DiscreteConditional, choose) {
+  DiscreteKey C(2, 2), D(4, 2), E(3, 2);
+  DiscreteConditional C_given_DE((C | D, E) = "4/1 1/1 1/1 1/4");
+
+  // Case 1: no given values: no-op
+  DiscreteValues given;
+  auto actual1 = C_given_DE.choose(given);
+  EXPECT(assert_equal(C_given_DE, *actual1, 1e-9));
+
+  // Case 2: 1 given value
+  given[D.first] = 1;
+  auto actual2 = C_given_DE.choose(given);
+  EXPECT_LONGS_EQUAL(1, actual2->nrFrontals());
+  EXPECT_LONGS_EQUAL(1, actual2->nrParents());
+  DiscreteConditional expected2(C | E = "1/1 1/4");
+  EXPECT(assert_equal(expected2, *actual2, 1e-9));
+
+  // Case 2: 2 given values
+  given[E.first] = 0;
+  auto actual3 = C_given_DE.choose(given);
+  EXPECT_LONGS_EQUAL(1, actual3->nrFrontals());
+  EXPECT_LONGS_EQUAL(0, actual3->nrParents());
+  DiscreteConditional expected3(C % "1/1");
+  EXPECT(assert_equal(expected3, *actual3, 1e-9));
+}
+
 /* ************************************************************************* */
 // Check markdown representation looks as expected, no parents.
 TEST(DiscreteConditional, markdown_prior) {