Fix Python wrapper cleanup and forward pass diagnostics

Release Python-owned wrapper references under the GIL so bound solver components are cleaned up safely. Also log partial forward-pass thread failures in verbose mode to make solver issues easier to diagnose.

Author: astomodynamics

python/src/bind_solver.cpp

@@ -42,9 +42,10 @@ void validateInitialTrajectory(cddp::CDDP &solver,
     try {
         state_dim = solver.getStateDim();
         control_dim = solver.getControlDim();
-    } catch (const std::exception &) {
+    } catch (const std::exception &e) {
         throw py::value_error(
-            "set_initial_trajectory requires a dynamical system to be set first.");
+            std::string("set_initial_trajectory failed while querying dimensions "
+                        "(is a dynamical system set?): ") + e.what());
     }
 
     const std::size_t expected_state_count =
@@ -95,6 +96,15 @@ class PythonBackedDynamicalSystem : public cddp::DynamicalSystem {
                                 wrapped->getIntegrationType()),
           owner_(std::move(owner)), wrapped_(wrapped) {}
 
+    ~PythonBackedDynamicalSystem() override {
+        try {
+            if (Py_IsInitialized()) {
+                py::gil_scoped_acquire gil;
+                owner_.release().dec_ref();
+            }
+        } catch (...) {}
+    }
+
     Eigen::VectorXd getContinuousDynamics(const Eigen::VectorXd &state,
                                           const Eigen::VectorXd &control,
                                           double time) const override {
@@ -163,6 +173,15 @@ class PythonBackedObjective : public cddp::Objective {
     PythonBackedObjective(py::object owner, cddp::Objective *wrapped)
         : owner_(std::move(owner)), wrapped_(wrapped) {}
 
+    ~PythonBackedObjective() override {
+        try {
+            if (Py_IsInitialized()) {
+                py::gil_scoped_acquire gil;
+                owner_.release().dec_ref();
+            }
+        } catch (...) {}
+    }
+
     double evaluate(const std::vector<Eigen::VectorXd> &states,
                     const std::vector<Eigen::VectorXd> &controls) const override {
         py::gil_scoped_acquire gil;
@@ -265,6 +284,15 @@ class PythonBackedConstraint : public cddp::Constraint {
         : cddp::Constraint(wrapped->getName()), owner_(std::move(owner)),
           wrapped_(wrapped) {}
 
+    ~PythonBackedConstraint() override {
+        try {
+            if (Py_IsInitialized()) {
+                py::gil_scoped_acquire gil;
+                owner_.release().dec_ref();
+            }
+        } catch (...) {}
+    }
+
     int getDualDim() const override {
         py::gil_scoped_acquire gil;
         return wrapped_->getDualDim();

src/cddp_core/cddp_solver_base.cpp

@@ -302,6 +302,11 @@ ForwardPassResult CDDPSolverBase::performForwardPass(CDDP &context) {
       std::cerr << getSolverName()
                 << ": ALL forward pass threads failed. Last error: "
                 << last_error << std::endl;
+    } else if (failed_count > 0 && options.verbose) {
+      std::cerr << getSolverName() << ": " << failed_count << " of "
+                << futures.size()
+                << " forward pass threads failed. Last error: " << last_error
+                << std::endl;
     }
     if (first_exception && !best_result.success) {
       std::rethrow_exception(first_exception);