integrators: add python bindings for dense integration

RobotLocomotion · Apr 11, 2020 · bf5c7d4 · bf5c7d4
1 parent d5019f2
commit bf5c7d4
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Showing 3 changed files with 31 additions and 2 deletions.
diff --git a/bindings/pydrake/systems/BUILD.bazel b/bindings/pydrake/systems/BUILD.bazel
@@ -400,6 +400,7 @@ drake_py_unittest(
         ":analysis_py",
         ":framework_py",
         ":primitives_py",
+        "//bindings/pydrake:trajectories_py",
     ],
 )
 

diff --git a/bindings/pydrake/systems/analysis_py.cc b/bindings/pydrake/systems/analysis_py.cc
@@ -57,7 +57,15 @@ PYBIND11_MODULE(analysis, m) {
             doc.IntegratorBase.set_throw_on_minimum_step_size_violation.doc)
         .def("get_throw_on_minimum_step_size_violation",
             &IntegratorBase<T>::get_throw_on_minimum_step_size_violation,
-            doc.IntegratorBase.get_throw_on_minimum_step_size_violation.doc);
+            doc.IntegratorBase.get_throw_on_minimum_step_size_violation.doc)
+        .def("StartDenseIntegration", &IntegratorBase<T>::StartDenseIntegration,
+            doc.IntegratorBase.StartDenseIntegration.doc)
+        .def("get_dense_output", &IntegratorBase<T>::get_dense_output,
+            py_reference_internal, doc.IntegratorBase.get_dense_output.doc)
+        .def("StopDenseIntegration", &IntegratorBase<T>::StopDenseIntegration,
+            // Keep alive, ownership (tr.): `return` keeps `self` alive.
+            py::keep_alive<1, 0>(),
+            doc.IntegratorBase.StopDenseIntegration.doc);
 
     DefineTemplateClassWithDefault<RungeKutta2Integrator<T>, IntegratorBase<T>>(
         m, "RungeKutta2Integrator", GetPyParam<T>(),

diff --git a/bindings/pydrake/systems/test/analysis_test.py b/bindings/pydrake/systems/test/analysis_test.py
@@ -8,8 +8,10 @@
 from pydrake.systems.analysis import (
     RungeKutta2Integrator_,
     RegionOfAttraction,
-    RegionOfAttractionOptions
+    RegionOfAttractionOptions,
+    Simulator
 )
+from pydrake.trajectories import PiecewisePolynomial
 
 
 class AnalysisTest(unittest.TestCase):
@@ -29,3 +31,21 @@ def test_symbolic_integrators(self):
 
         max_h = 0.1
         RungeKutta2Integrator_[Expression](sys, max_h, context)
+
+    def test_dense_integration(self):
+        x = Variable("x")
+        sys = SymbolicVectorSystem(state=[x], dynamics=[-x+x**3])
+        simulator = Simulator(sys)
+        integrator = simulator.get_mutable_integrator()
+        self.assertIsNone(integrator.get_dense_output())
+        integrator.StartDenseIntegration()
+        # If I include the following line, then I get a RuntimeError
+        # on StopDenseIntegration()
+        # a = integrator.get_dense_output()
+        self.assertIsInstance(integrator.get_dense_output(),
+                              PiecewisePolynomial)
+        simulator.AdvanceTo(1.0)
+        pp = integrator.StopDenseIntegration()
+        self.assertEqual(pp.start_time(), 0.0)
+        self.assertEqual(pp.end_time(), 1.0)
+        self.assertIsNone(integrator.get_dense_output())