Using return_value_policy::reference

Former-commit-id: f1a8431e86

stormpy/src/storage/matrix.cpp

@@ -19,7 +19,7 @@ void define_sparse_matrix(py::module& m) {
     ;
  
     py::class_<storm::storage::SparseMatrix<double>>(m, "SparseMatrix", "Sparse matrix")
-        .def("__iter__", [](storm::storage::SparseMatrix<double> const& matrix) {
+        .def("__iter__", [](storm::storage::SparseMatrix<double>& matrix) {
                 return py::make_iterator(matrix.begin(), matrix.end());
             }, py::keep_alive<0, 1>() /* Essential: keep object alive while iterator exists */)
         .def("__str__", [](storm::storage::SparseMatrix<double> const& matrix) {
@@ -37,7 +37,7 @@ void define_sparse_matrix(py::module& m) {
         .def("get_rows", [](storm::storage::SparseMatrix<double>& matrix, entry_index start, entry_index end) {
                 return matrix.getRows(start, end);
             }, "Get rows from start to end")
-        .def("print_row", [](storm::storage::SparseMatrix<double>& matrix, entry_index row) {
+        .def("print_row", [](storm::storage::SparseMatrix<double> const& matrix, entry_index row) {
                 std::stringstream stream;
                 auto rows = matrix.getRows(row, row+1);
                 for (auto transition : rows) {

stormpy/src/storage/model.cpp

@@ -17,7 +17,7 @@ std::vector<storm::storage::sparse::state_type> getInitialStates(storm::models::
 }
 
 // Thin wrapper for getting transition matrix
-storm::storage::SparseMatrix<double> getTransitionMatrix(storm::models::sparse::Model<double> const& model) {
+storm::storage::SparseMatrix<double>& getTransitionMatrix(storm::models::sparse::Model<double>& model) {
     return model.getTransitionMatrix();
 }
 
@@ -53,7 +53,7 @@ void define_model(py::module& m) {
             }, "Get labels")
         .def("labels_state", &storm::models::sparse::Model<double>::getLabelsOfState, "Get labels")
         .def("initial_states", &getInitialStates<double>, "Get initial states")
-        .def("transition_matrix", &getTransitionMatrix, "Get transition matrix")
+        .def("transition_matrix", &getTransitionMatrix, py::return_value_policy::reference, py::keep_alive<1, 0>(), "Get transition matrix")
     ;    
     py::class_<storm::models::sparse::Dtmc<double>, std::shared_ptr<storm::models::sparse::Dtmc<double>>>(m, "SparseDtmc", "DTMC in sparse representation", py::base<storm::models::sparse::Model<double>>())
     ;

stormpy/tests/storage/test_matrix.py

@@ -24,3 +24,42 @@ class TestMatrix:
         for e in matrix:
             assert e.val() == i
             i += 0.1
+    
+    def test_change_sparse_matrix_modelchecking(self):
+        import stormpy.logic
+        model = stormpy.parse_explicit_model("../examples/dtmc/die/die.tra", "../examples/dtmc/die/die.lab")
+        matrix = model.transition_matrix()
+        # Check matrix
+        for e in matrix:
+            assert e.val() == 0.5 or e.val() == 0 or e.val() == 1
+        # First model checking
+        formulas = stormpy.parse_formulas("P=? [ F \"one\" ]")
+        result = stormpy.model_checking(model, formulas[0])
+        assert result == 0.16666666666666663
+        
+        # Change probabilities
+        i = 0
+        for e in matrix:
+            if e.val() == 0.5:
+                if i % 2 == 0:
+                    e.set_val(0.3)
+                else:
+                    e.set_val(0.7)
+                i += 1
+        for e in matrix:
+            assert e.val() == 0.3 or e.val() == 0.7 or e.val() == 1 or e.val() == 0
+        # Second model checking
+        result = stormpy.model_checking(model, formulas[0])
+        assert result == 0.06923076923076932
+        
+        # Change probabilities again
+        for state in stormpy.state.State(0, model):
+            for action in state.actions():
+                for transition in action.transitions():
+                    if transition.val() == 0.3:
+                        transition.set_val(0.8)
+                    elif transition.val() == 0.7:
+                        transition.set_val(0.2)
+        # Third model checking
+        result = stormpy.model_checking(model, formulas[0])
+        assert result == 0.3555555555555556 or result == 0.3555555555555557