Fix generatedNodes benchmark bug (#411)

src/heuristic/HeuristicMapper.cpp

@@ -672,8 +672,7 @@ HeuristicMapper::Node HeuristicMapper::aStarMap(size_t layer, bool reverse) {
     const std::chrono::duration<double> diff = end - start;
     results.heuristicBenchmark.secondsPerNode += diff.count();
 
-    layerResultsIt->generatedNodes =
-        layerResultsIt->expandedNodes + nodes.size();
+    layerResultsIt->generatedNodes = nextNodeId;
     results.heuristicBenchmark.generatedNodes += layerResultsIt->generatedNodes;
 
     if (layerResultsIt->expandedNodes > 0) {

test/test_heuristic.cpp

@@ -165,6 +165,34 @@ TEST(Functionality, EmptyDump) {
   EXPECT_THROW(mapper.dumpResult("test.dummy"), QMAPException);
 }
 
+TEST(Functionality, BenchmarkGeneratedNodes) {
+  qc::QuantumComputation qc{16, 16};
+  qc.cx(qc::Control{0}, 6);
+  for (std::size_t i = 0; i < 16; ++i) {
+    qc.measure(static_cast<qc::Qubit>(i), i);
+  }
+  Architecture ibmQX5{};
+  ibmQX5.loadCouplingMap(AvailableArchitecture::IbmQx5);
+  auto ibmQX5Mapper = std::make_unique<HeuristicMapper>(qc, ibmQX5);
+
+  Configuration settings{};
+  settings.admissibleHeuristic      = true;
+  settings.lookahead                = false;
+  settings.layering                 = Layering::IndividualGates;
+  settings.automaticLayerSplits     = false;
+  settings.initialLayout            = InitialLayout::Identity;
+  settings.preMappingOptimizations  = false;
+  settings.postMappingOptimizations = false;
+  settings.considerFidelity         = false;
+  settings.useTeleportation         = false;
+  settings.debug                    = true;
+  ibmQX5Mapper->map(settings);
+  auto results = ibmQX5Mapper->getResults();
+
+  EXPECT_EQ(results.heuristicBenchmark.generatedNodes, 30);
+  EXPECT_EQ(results.layerHeuristicBenchmark.at(0).generatedNodes, 30);
+}
+
 TEST(Functionality, InvalidSettings) {
   qc::QuantumComputation qc{1};
   qc.x(0);