Picking a default SmtSolver, even if no CoreSettings are available.

src/storm/utility/solver.cpp

@@ -18,6 +18,7 @@
 #include "storm/utility/NumberTraits.h"
 
 #include "storm/exceptions/InvalidSettingsException.h"
+#include "storm/exceptions/InvalidOperationException.h"
 
 namespace storm {
     namespace utility {
@@ -89,7 +90,18 @@ namespace storm {
             }
             
             std::unique_ptr<storm::solver::SmtSolver> SmtSolverFactory::create(storm::expressions::ExpressionManager& manager) const {
-                storm::solver::SmtSolverType smtSolverType = storm::settings::getModule<storm::settings::modules::CoreSettings>().getSmtSolver();
+                storm::solver::SmtSolverType smtSolverType;
+                if (storm::settings::hasModule<storm::settings::modules::CoreSettings>()) {
+                     smtSolverType = storm::settings::getModule<storm::settings::modules::CoreSettings>().getSmtSolver();
+                } else {
+#ifdef STORM_HAVE_Z3
+                    smtSolverType = storm::solver::SmtSolverType::Z3;
+#elif STORM_HAVE_MSAT
+                    smtSolverType = storm::solver::SmtSolverType::Mathsat;
+#else
+                    STORM_LOG_THROW(false, storm::exceptions::InvalidOperationException, "Requested an SMT solver but none was installed.");
+#endif
+                }
                 switch (smtSolverType) {
                     case storm::solver::SmtSolverType::Z3: return std::unique_ptr<storm::solver::SmtSolver>(new storm::solver::Z3SmtSolver(manager));
                     case storm::solver::SmtSolverType::Mathsat: return std::unique_ptr<storm::solver::SmtSolver>(new storm::solver::MathsatSmtSolver(manager));