Replaces pointer versions of get_integrator() and get_mutable_integra…

…tor().

attic/manipulation/dev/quasistatic_iiwa_pick_and_place_demo.cc

@@ -285,7 +285,7 @@ int do_main() {
   x0.SetAtIndex(15, 0.055);            // right gripper
 
   simulator.set_target_realtime_rate(0);
-  simulator.get_mutable_integrator()->set_maximum_step_size(h);
+  simulator.get_mutable_integrator().set_maximum_step_size(h);
   simulator.Initialize();
   simulator.AdvanceTo(kTimes.back());
 

attic/manipulation/dev/test/rod2d_time_stepping.cc

@@ -202,7 +202,7 @@ VectorXd RunSimulation(const bool is_analytic) {
 
   simulator.set_target_realtime_rate(0);
   const double h = rod2d->get_period_sec();
-  simulator.get_mutable_integrator()->set_maximum_step_size(h);
+  simulator.get_mutable_integrator().set_maximum_step_size(h);
   simulator.Initialize();
   simulator.AdvanceTo(7.5);
 

attic/manipulation/scene_generation/simulate_plant_to_rest.cc

@@ -90,8 +90,8 @@ VectorX<double> SimulatePlantToRest::Run(const VectorX<double>& q_ik,
 
     simulator.reset_integrator<systems::RungeKutta2Integrator<double>>(
         *diagram_, 0.0001, &simulator.get_mutable_context());
-    simulator.get_mutable_integrator()->set_maximum_step_size(max_step_size);
-    simulator.get_mutable_integrator()->set_fixed_step_mode(true);
+    simulator.get_mutable_integrator().set_maximum_step_size(max_step_size);
+    simulator.get_mutable_integrator().set_fixed_step_mode(true);
     step_time = 1.0;
     step_delta = 0.1;
     do {

attic/systems/sensors/test/accelerometer_test/accelerometer_test.cc

@@ -148,7 +148,7 @@ GTEST_TEST(TestAccelerometer, TestSensorAttachedToSwingingPendulum) {
   Simulator<double> simulator(diagram, std::move(context));
   // Decrease the step size to get x_dot(0) to be closer to x(1).
   const double stepSize = 1e-4;
-  simulator.get_mutable_integrator()->set_maximum_step_size(stepSize);
+  simulator.get_mutable_integrator().set_maximum_step_size(stepSize);
   simulator.Initialize();
 
   const AccelerometerTestLogger& logger = diagram.get_logger();

automotive/automotive_simulator.cc

@@ -730,7 +730,7 @@ void AutomotiveSimulator<T>::Start(
   const double max_step_size = 0.01;
   simulator_->template reset_integrator<RungeKutta2Integrator<T>>(
       *diagram_, max_step_size, &simulator_->get_mutable_context());
-  simulator_->get_mutable_integrator()->set_fixed_step_mode(true);
+  simulator_->get_mutable_integrator().set_fixed_step_mode(true);
   simulator_->Initialize();
 }
 

automotive/maliput/multilane/road_curve.cc

@@ -133,11 +133,11 @@ RoadCurve::RoadCurve(double linear_tolerance, double scale_length,
   // accuracy balance). However, for the time being, the following
   // constants (considering 0.0 <= p <= 1.0) work well as a heuristic
   // approximation to appropriate step sizes.
-  systems::IntegratorBase<double>* s_from_p_integrator =
+  systems::IntegratorBase<double>& s_from_p_integrator =
       s_from_p_func_->get_mutable_integrator();
-  s_from_p_integrator->request_initial_step_size_target(0.1);
-  s_from_p_integrator->set_maximum_step_size(1.0);
-  s_from_p_integrator->set_target_accuracy(relative_tolerance_);
+  s_from_p_integrator.request_initial_step_size_target(0.1);
+  s_from_p_integrator.set_maximum_step_size(1.0);
+  s_from_p_integrator.set_target_accuracy(relative_tolerance_);
 
   // Sets `p_from_s`'s integration accuracy and step sizes. Said steps
   // should not be too large, because that could make accuracy control
@@ -146,11 +146,11 @@ RoadCurve::RoadCurve(double linear_tolerance, double scale_length,
   // optimal step sizes (in terms of their efficiency vs. accuracy balance).
   // However, for the time being, the following proportions of the scale
   // length work well as a heuristic approximation to appropriate step sizes.
-  systems::IntegratorBase<double>* p_from_s_integrator =
+  systems::IntegratorBase<double>& p_from_s_integrator =
       p_from_s_ivp_->get_mutable_integrator();
-  p_from_s_integrator->request_initial_step_size_target(0.1 * scale_length);
-  p_from_s_integrator->set_maximum_step_size(scale_length);
-  p_from_s_integrator->set_target_accuracy(relative_tolerance_);
+  p_from_s_integrator.request_initial_step_size_target(0.1 * scale_length);
+  p_from_s_integrator.set_maximum_step_size(scale_length);
+  p_from_s_integrator.set_target_accuracy(relative_tolerance_);
 }
 
 bool RoadCurve::AreFastComputationsAccurate(double r) const {

examples/acrobot/run_lqr_w_estimator.cc

@@ -134,8 +134,8 @@ int do_main() {
 
   // Simulate.
   simulator.set_target_realtime_rate(FLAGS_realtime_factor);
-  simulator.get_mutable_integrator()->set_maximum_step_size(0.01);
-  simulator.get_mutable_integrator()->set_fixed_step_mode(true);
+  simulator.get_mutable_integrator().set_maximum_step_size(0.01);
+  simulator.get_mutable_integrator().set_fixed_step_mode(true);
   simulator.Initialize();
   simulator.AdvanceTo(FLAGS_simulation_sec);
 

examples/bouncing_ball/test/bouncing_ball_test.cc

@@ -166,8 +166,8 @@ TEST_F(BouncingBallTest, Simulate) {
   simulator.reset_integrator<systems::RungeKutta3Integrator<double>>(*dut_,
       &simulator.get_mutable_context());
   simulator.get_mutable_context().SetAccuracy(accuracy);
-  simulator.get_mutable_integrator()->request_initial_step_size_target(1e-3);
-  simulator.get_mutable_integrator()->set_target_accuracy(accuracy);
+  simulator.get_mutable_integrator().request_initial_step_size_target(1e-3);
+  simulator.get_mutable_integrator().set_target_accuracy(accuracy);
   simulator.Initialize();
 
   // Set the initial state for the bouncing ball.

examples/contact_model/rigid_gripper.cc

@@ -146,8 +146,8 @@ int main() {
   systems::Context<double>& context = simulator.get_mutable_context();
 
   simulator.reset_integrator<RungeKutta3Integrator<double>>(*model, &context);
-  simulator.get_mutable_integrator()->request_initial_step_size_target(1e-4);
-  simulator.get_mutable_integrator()->set_target_accuracy(FLAGS_accuracy);
+  simulator.get_mutable_integrator().request_initial_step_size_target(1e-4);
+  simulator.get_mutable_integrator().set_target_accuracy(FLAGS_accuracy);
   std::cout << "Variable-step integrator accuracy: " << FLAGS_accuracy << "\n";
 
   simulator.Initialize();

examples/kuka_iiwa_arm/controlled_kuka/controlled_kuka_multibody_demo.cc

@@ -101,7 +101,7 @@ int DoMain() {
   systems::Simulator<double> simulator(*diagram);
   simulator.Initialize();
   simulator.set_target_realtime_rate(1.0);
-  simulator.get_mutable_integrator()->set_target_accuracy(1e-3);
+  simulator.get_mutable_integrator().set_target_accuracy(1e-3);
 
   simulator.AdvanceTo(FLAGS_simulation_sec);
   return 0;

examples/manipulation_station/differential_ik.py

@@ -39,15 +39,15 @@ def __init__(self, robot, frame_E, parameters, time_step):
             self.robot_context)[-robot.num_velocities():].any()
 
         # Store the robot positions as state.
-        self._DeclareDiscreteState(robot.num_positions())
-        self._DeclarePeriodicDiscreteUpdate(time_step)
+        self.DeclareDiscreteState(robot.num_positions())
+        self.DeclarePeriodicDiscreteUpdate(time_step)
 
         # Desired pose of frame E in world frame.
-        self._DeclareInputPort("rpy_xyz_desired",
-                               PortDataType.kVectorValued, 6)
+        self.DeclareInputPort("rpy_xyz_desired",
+                              PortDataType.kVectorValued, 6)
 
         # Provide the output as desired positions.
-        self._DeclareVectorOutputPort("joint_position_desired", BasicVector(
+        self.DeclareVectorOutputPort("joint_position_desired", BasicVector(
             robot.num_positions()), self.CopyPositionOut)
 
     def SetPositions(self, context, q):

examples/manipulation_station/end_effector_teleop_mouse.py

@@ -123,16 +123,16 @@ def get_events(self):
 class MouseKeyboardTeleop(LeafSystem):
     def __init__(self, grab_focus=True):
         LeafSystem.__init__(self)
-        self._DeclareVectorOutputPort("rpy_xyz", BasicVector(6),
-                                      self._DoCalcOutput)
-        self._DeclareVectorOutputPort("position", BasicVector(1),
-                                      self.CalcPositionOutput)
-        self._DeclareVectorOutputPort("force_limit", BasicVector(1),
-                                      self.CalcForceLimitOutput)
+        self.DeclareVectorOutputPort("rpy_xyz", BasicVector(6),
+                                     self._DoCalcOutput)
+        self.DeclareVectorOutputPort("position", BasicVector(1),
+                                     self.CalcPositionOutput)
+        self.DeclareVectorOutputPort("force_limit", BasicVector(1),
+                                     self.CalcForceLimitOutput)
 
         # Note: This timing affects the keyboard teleop performance. A larger
         #       time step causes more lag in the response.
-        self._DeclarePeriodicPublish(0.01, 0.0)
+        self.DeclarePeriodicPublish(0.01, 0.0)
 
         self.teleop_manager = TeleopMouseKeyboardManager(grab_focus=grab_focus)
         self.roll = self.pitch = self.yaw = 0

examples/multibody/inclined_plane_with_body/inclined_plane_with_body.cc

@@ -162,12 +162,12 @@ int do_main() {
   plant.SetFreeBodyPoseInWorldFrame(&plant_context, bodyB, X_WB);
 
   systems::Simulator<double> simulator(*diagram, std::move(diagram_context));
-  systems::IntegratorBase<double>* integrator =
+  systems::IntegratorBase<double>& integrator =
       simulator.get_mutable_integrator();
 
   // Set the integration accuracy when the plant is integrated with a variable-
   // step integrator. This value is not used if time_step > 0 (fixed-time step).
-  integrator->set_target_accuracy(FLAGS_integration_accuracy);
+  integrator.set_target_accuracy(FLAGS_integration_accuracy);
 
   simulator.set_publish_every_time_step(false);
   simulator.set_target_realtime_rate(FLAGS_target_realtime_rate);

examples/quadrotor/run_quadrotor_lqr.cc

@@ -77,7 +77,7 @@ int do_main() {
 
     // The following accuracy is necessary for the example to satisfy its
     // ending state tolerances.
-    simulator.get_mutable_integrator()->set_target_accuracy(5e-5);
+    simulator.get_mutable_integrator().set_target_accuracy(5e-5);
     simulator.AdvanceTo(FLAGS_trial_duration);
 
     // Goal state verification.

examples/rod2d/rod2d_sim.cc

@@ -136,8 +136,8 @@ int main(int argc, char* argv[]) {
     simulator.reset_integrator<RungeKutta3Integrator<double>>(*diagram,
                                                               &mut_context);
   }
-  simulator.get_mutable_integrator()->set_target_accuracy(FLAGS_accuracy);
-  simulator.get_mutable_integrator()->set_maximum_step_size(FLAGS_dt);
+  simulator.get_mutable_integrator().set_target_accuracy(FLAGS_accuracy);
+  simulator.get_mutable_integrator().set_maximum_step_size(FLAGS_dt);
 
   // Start simulating.
   simulator.set_target_realtime_rate(1.0);

examples/scene_graph/bouncing_ball_run_dynamics.cc

@@ -89,7 +89,7 @@ int do_main() {
   init_ball(bouncing_ball1, 0.3, 0.);
   init_ball(bouncing_ball2, 0.3, 0.3);
 
-  simulator.get_mutable_integrator()->set_maximum_step_size(0.002);
+  simulator.get_mutable_integrator().set_maximum_step_size(0.002);
   simulator.set_target_realtime_rate(1.f);
   simulator.Initialize();
   simulator.AdvanceTo(FLAGS_simulation_time);

examples/scene_graph/dev/bouncing_ball_run_dynamics.cc

@@ -176,7 +176,7 @@ int do_main() {
   init_ball(bouncing_ball1, 0.3, 0.);
   init_ball(bouncing_ball2, 0.3, 0.3);
 
-  simulator.get_mutable_integrator()->set_maximum_step_size(0.002);
+  simulator.get_mutable_integrator().set_maximum_step_size(0.002);
   simulator.Initialize();
   simulator.set_publish_every_time_step(false);
   simulator.set_publish_at_initialization(false);

examples/scene_graph/dev/solar_system_run_dynamics.cc

@@ -37,7 +37,7 @@ int do_main() {
 
   systems::Simulator<double> simulator(*diagram);
 
-  simulator.get_mutable_integrator()->set_maximum_step_size(0.002);
+  simulator.get_mutable_integrator().set_maximum_step_size(0.002);
   simulator.set_publish_every_time_step(false);
   simulator.set_target_realtime_rate(1);
   simulator.Initialize();

examples/scene_graph/solar_system_run_dynamics.cc

@@ -36,7 +36,7 @@ int do_main() {
 
   systems::Simulator<double> simulator(*diagram);
 
-  simulator.get_mutable_integrator()->set_maximum_step_size(0.002);
+  simulator.get_mutable_integrator().set_maximum_step_size(0.002);
   simulator.set_publish_every_time_step(false);
   simulator.set_target_realtime_rate(1);
   simulator.Initialize();

multibody/plant/test/inclined_plane_test.cc

@@ -135,8 +135,8 @@ TEST_P(InclinedPlaneTest, RollingSphereTest) {
   plant.SetFreeBodyPoseInWorldFrame(&plant_context, ball, X_WB_initial);
 
   Simulator<double> simulator(*diagram, std::move(diagram_context));
-  IntegratorBase<double>* integrator = simulator.get_mutable_integrator();
-  integrator->set_target_accuracy(target_accuracy);
+  IntegratorBase<double>& integrator = simulator.get_mutable_integrator();
+  integrator.set_target_accuracy(target_accuracy);
   simulator.set_publish_every_time_step(true);
   simulator.Initialize();
   simulator.AdvanceTo(simulation_time);

multibody/plant/test/spring_mass_system_test.cc

@@ -141,7 +141,7 @@ TEST_F(SpringMassSystemTest, UnDampedCase) {
   slider_->set_translation(&context, free_length_ + amplitude);
   slider_->set_translation_rate(&context, 0.0);
   simulator.Initialize();
-  simulator.get_mutable_integrator()->set_target_accuracy(integration_accuracy);
+  simulator.get_mutable_integrator().set_target_accuracy(integration_accuracy);
   simulator.AdvanceTo(simulation_time);
 
   const double x_analytic = CalcAnalyticSolution(
@@ -172,7 +172,7 @@ TEST_F(SpringMassSystemTest, UnderDampedCase) {
   slider_->set_translation(&context, free_length_ + amplitude);
   slider_->set_translation_rate(&context, 0.0);
   simulator.Initialize();
-  simulator.get_mutable_integrator()->set_target_accuracy(integration_accuracy);
+  simulator.get_mutable_integrator().set_target_accuracy(integration_accuracy);
   simulator.AdvanceTo(simulation_time);
 
   const double x_analytic = CalcAnalyticSolution(
@@ -203,7 +203,7 @@ TEST_F(SpringMassSystemTest, OverDampedCase) {
   slider_->set_translation(&context, free_length_ + amplitude);
   slider_->set_translation_rate(&context, 0.0);
   simulator.Initialize();
-  simulator.get_mutable_integrator()->set_target_accuracy(integration_accuracy);
+  simulator.get_mutable_integrator().set_target_accuracy(integration_accuracy);
   simulator.AdvanceTo(simulation_time);
 
   const double x_analytic = CalcAnalyticSolution(

systems/analysis/BUILD.bazel

@@ -255,6 +255,7 @@ drake_cc_googletest(
         ":implicit_euler_integrator",
         ":runge_kutta3_integrator",
         ":simulator",
+        "//common/test_utilities:expect_throws_message",
         "//common/test_utilities:is_dynamic_castable",
         "//systems/analysis/test_utilities",
         "//systems/primitives",

systems/analysis/antiderivative_function.h

@@ -196,13 +196,13 @@ class AntiderivativeFunction {
         std::forward<Args>(args)...);
   }
 
-  /// Gets a pointer to the internal integrator instance.
-  const IntegratorBase<T>* get_integrator() const {
+  /// Gets a reference to the internal integrator instance.
+  const IntegratorBase<T>& get_integrator() const {
     return scalar_ivp_->get_integrator();
   }
 
-  /// Gets a pointer to the internal mutable integrator instance.
-  IntegratorBase<T>* get_mutable_integrator() {
+  /// Gets a mutable reference to the internal integrator instance.
+  IntegratorBase<T>& get_mutable_integrator() {
     return scalar_ivp_->get_mutable_integrator();
   }
 

systems/analysis/initial_value_problem.h

@@ -200,14 +200,16 @@ class InitialValueProblem {
     return static_cast<Integrator*>(integrator_.get());
   }
 
-  /// Gets a pointer to the internal integrator instance.
-  const IntegratorBase<T>* get_integrator() const {
-    return integrator_.get();
+  /// Gets a reference to the internal integrator instance.
+  const IntegratorBase<T>& get_integrator() const {
+    DRAKE_DEMAND(integrator_.get());
+    return *integrator_.get();
   }
 
-  /// Gets a pointer to the internal mutable integrator instance.
-  IntegratorBase<T>* get_mutable_integrator() {
-    return integrator_.get();
+  /// Gets a mutable reference to the internal integrator instance.
+  IntegratorBase<T>& get_mutable_integrator() {
+    DRAKE_DEMAND(integrator_.get());
+    return *integrator_.get();
   }
 
  private:

systems/analysis/scalar_initial_value_problem.h

@@ -194,13 +194,13 @@ class ScalarInitialValueProblem {
         std::forward<Args>(args)...);
   }
 
-  /// Gets a pointer to the internal integrator instance.
-  const IntegratorBase<T>* get_integrator() const {
+  /// Gets a reference to the internal integrator instance.
+  const IntegratorBase<T>& get_integrator() const {
     return vector_ivp_->get_integrator();
   }
 
-  /// Gets a pointer to the internal mutable integrator instance.
-  IntegratorBase<T>* get_mutable_integrator() {
+  /// Gets a mutable reference to the internal integrator instance.
+  IntegratorBase<T>& get_mutable_integrator() {
     return vector_ivp_->get_mutable_integrator();
   }
 

systems/analysis/simulator.h

@@ -464,13 +464,13 @@ class Simulator {
   int64_t get_num_unrestricted_updates() const {
     return num_unrestricted_updates_; }
 
-  /// Gets a pointer to the integrator used to advance the continuous aspects
+  /// Gets a reference to the integrator used to advance the continuous aspects
   /// of the system.
-  const IntegratorBase<T>* get_integrator() const { return integrator_.get(); }
+  const IntegratorBase<T>& get_integrator() const { return *integrator_.get(); }
 
-  /// Gets a pointer to the mutable integrator used to advance the continuous
-  /// aspects of the system.
-  IntegratorBase<T>* get_mutable_integrator() { return integrator_.get(); }
+  /// Gets a reference to the mutable integrator used to advance the continuous
+  /// state of the system.
+  IntegratorBase<T>& get_mutable_integrator() { return *integrator_.get(); }
 
   /// Resets the integrator with a new one. An example usage is:
   /// @code
@@ -480,8 +480,11 @@ class Simulator {
   /// ensure the integrator is properly initialized. You can do that explicitly
   /// with the Initialize() method or it will be done implicitly at the first
   /// time step.
+  /// @throws std::logic_error if `integrator` is nullptr.
   template <class U>
   U* reset_integrator(std::unique_ptr<U> integrator) {
+    if (!integrator)
+      throw std::logic_error("Integrator cannot be null.");
     initialization_done_ = false;
     integrator_ = std::move(integrator);
     return static_cast<U*>(integrator_.get());