Increase linear solution mode heuristic barrier

When automatically selecting the linear solution mode of a model
system, the heuristic is solely based on the number of unit operations.
Of course, the parallel approach is chosen if any cycle is present in
the system.

If the system consists of at least 6 unit operations, parallel solution
mode is selected. Based on observations, this number is far too low in
practice. Hence, the barrier is bumped up to 25 unit operations.

Closes #103.

src/libcadet/model/ModelSystemImpl.cpp

@@ -818,15 +818,15 @@ void ModelSystem::configureSwitches(IParameterProvider& paramProvider)
 
 			// TODO: Add heuristic for number and complexity of unit operations
 
-			// Simple heuristic: At least 6 models (regardless of complexity) => Parallelize
-			if (_models.size() >= 6)
+			// Simple heuristic: At least 25 models (regardless of complexity) => Parallelize
+			if (_models.size() >= 25)
 			{
 				_linearModelOrdering.pushBackSlice(0);
-				LOG(Debug) << "Select parallel solution method for switch " << i << " (at least 6 models)";
+				LOG(Debug) << "Select parallel solution method for switch " << i << " (at least 25 models)";
 			}
 			else
 			{
-				// Less than 6 models => Select depending on existence of cycles
+				// Less than 25 models => Select depending on existence of cycles
 				const util::SlicedVector<int> adjList = graph::adjacencyListFromConnectionList(conn.data(), _models.size(), conn.size() / 6);
 				std::vector<int> topoOrder;
 				const bool hasCycles = graph::topologicalSort(adjList, topoOrder);