Add test for combine

gtsam/discrete/tests/testDecisionTreeFactor.cpp

@@ -174,6 +174,70 @@ TEST(DecisionTreeFactor, Prune) {
   EXPECT(assert_equal(expected3, pruned3));
 }
 
+/* ************************************************************************** */
+// Asia Bayes Network
+/* ************************************************************************** */
+
+#define DISABLE_DOT
+
+void maybeSaveDotFile(const DecisionTreeFactor& f, const string& filename) {
+#ifndef DISABLE_DOT
+  std::vector<std::string> names = {"A", "S", "T", "L", "B", "E", "X", "D"};
+  auto formatter = [&](Key key) { return names[key]; };
+  f.dot(filename, formatter, true);
+#endif
+}
+
+/** Convert Signature into CPT */
+DecisionTreeFactor create(const Signature& signature) {
+  DecisionTreeFactor p(signature.discreteKeys(), signature.cpt());
+  return p;
+}
+
+/* ************************************************************************* */
+// test Asia Joint
+TEST(DecisionTreeFactor, joint) {
+  DiscreteKey A(0, 2), S(1, 2), T(2, 2), L(3, 2), B(4, 2), E(5, 2), X(6, 2),
+      D(7, 2);
+
+  gttic_(asiaCPTs);
+  DecisionTreeFactor pA = create(A % "99/1");
+  DecisionTreeFactor pS = create(S % "50/50");
+  DecisionTreeFactor pT = create(T | A = "99/1 95/5");
+  DecisionTreeFactor pL = create(L | S = "99/1 90/10");
+  DecisionTreeFactor pB = create(B | S = "70/30 40/60");
+  DecisionTreeFactor pE = create((E | T, L) = "F T T T");
+  DecisionTreeFactor pX = create(X | E = "95/5 2/98");
+  DecisionTreeFactor pD = create((D | E, B) = "9/1 2/8 3/7 1/9");
+
+  // Create joint
+  gttic_(asiaJoint);
+  DecisionTreeFactor joint = pA;
+  maybeSaveDotFile(joint, "Asia-A");
+  joint = joint * pS;
+  maybeSaveDotFile(joint, "Asia-AS");
+  joint = joint * pT;
+  maybeSaveDotFile(joint, "Asia-AST");
+  joint = joint * pL;
+  maybeSaveDotFile(joint, "Asia-ASTL");
+  joint = joint * pB;
+  maybeSaveDotFile(joint, "Asia-ASTLB");
+  joint = joint * pE;
+  maybeSaveDotFile(joint, "Asia-ASTLBE");
+  joint = joint * pX;
+  maybeSaveDotFile(joint, "Asia-ASTLBEX");
+  joint = joint * pD;
+  maybeSaveDotFile(joint, "Asia-ASTLBEXD");
+
+  // Check that discrete keys are as expected
+  EXPECT(assert_equal(joint.discreteKeys(), {A, S, T, L, B, E, X, D}));
+
+  // Check that summing out variables maintains the keys even if merged, as is
+  // the case with S.
+  auto noAB = joint.sum(Ordering{A.first, B.first});
+  EXPECT(assert_equal(noAB->discreteKeys(), {S, T, L, E, X, D}));
+}
+
 /* ************************************************************************* */
 TEST(DecisionTreeFactor, DotWithNames) {
   DiscreteKey A(12, 3), B(5, 2);