From a15d5fa21382edd367203bf04456887b07b6445a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-No=C3=ABl=20Grad?= <jgrad@icp.uni-stuttgart.de>
Date: Tue, 9 May 2023 18:22:33 +0200
Subject: [PATCH 1/2] script_interface: Rewrite ObjectList as AutoParameters

---
 src/python/espressomd/script_interface.pyx    | 27 --------
 src/script_interface/ObjectContainer.hpp      | 42 ++++++++++++
 src/script_interface/ObjectList.hpp           | 65 ++++++++-----------
 .../tests/serialization_mpi_guard_test.cpp    | 21 +++---
 testsuite/python/save_checkpoint.py           |  5 +-
 testsuite/python/test_checkpoint.py           | 49 +++++++++-----
 6 files changed, 111 insertions(+), 98 deletions(-)
 create mode 100644 src/script_interface/ObjectContainer.hpp

diff --git a/src/python/espressomd/script_interface.pyx b/src/python/espressomd/script_interface.pyx
index 940c1f3e2cb..458d5eb1e61 100644
--- a/src/python/espressomd/script_interface.pyx
+++ b/src/python/espressomd/script_interface.pyx
@@ -457,15 +457,6 @@ class ScriptObjectList(ScriptInterfaceHelper):
 
     """
 
-    def __init__(self, *args, **kwargs):
-        if args:
-            params, (_unpickle_so_class, (_so_name, bytestring)) = args
-            assert _so_name == self._so_name
-            self = _unpickle_so_class(_so_name, bytestring)
-            self.__setstate__(params)
-        else:
-            super().__init__(**kwargs)
-
     def __getitem__(self, key):
         return self.call_method("get_elements")[key]
 
@@ -477,24 +468,6 @@ class ScriptObjectList(ScriptInterfaceHelper):
     def __len__(self):
         return self.call_method("size")
 
-    @classmethod
-    def _restore_object(cls, so_callback, so_callback_args, state):
-        so = so_callback(*so_callback_args)
-        so.__setstate__(state)
-        return so
-
-    def __reduce__(self):
-        so_callback, (so_name, so_bytestring) = super().__reduce__()
-        return (ScriptObjectList._restore_object,
-                (so_callback, (so_name, so_bytestring), self.__getstate__()))
-
-    def __getstate__(self):
-        return self.call_method("get_elements")
-
-    def __setstate__(self, object_list):
-        for item in object_list:
-            self.add(item)
-
 
 class ScriptObjectMap(ScriptInterfaceHelper):
     """
diff --git a/src/script_interface/ObjectContainer.hpp b/src/script_interface/ObjectContainer.hpp
new file mode 100644
index 00000000000..f5a8e89e2da
--- /dev/null
+++ b/src/script_interface/ObjectContainer.hpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2023 The ESPResSo project
+ *
+ * This file is part of ESPResSo.
+ *
+ * ESPResSo is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * ESPResSo is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef SCRIPT_INTERFACE_OBJECT_CONTAINER_HPP
+#define SCRIPT_INTERFACE_OBJECT_CONTAINER_HPP
+
+#include "script_interface/auto_parameters/AutoParameters.hpp"
+
+#include <type_traits>
+
+namespace ScriptInterface {
+
+/**
+ * @brief Base class for containers whose @c BaseType might be a full
+ * specialization of @ref AutoParameters.
+ */
+template <template <typename...> class Container, typename ManagedType,
+          class BaseType,
+          class =
+              std::enable_if_t<std::is_base_of_v<ObjectHandle, ManagedType>>>
+using ObjectContainer = std::conditional_t<
+    std::is_same_v<BaseType, ObjectHandle>,
+    AutoParameters<Container<ManagedType, BaseType>, BaseType>, BaseType>;
+
+} // namespace ScriptInterface
+
+#endif
diff --git a/src/script_interface/ObjectList.hpp b/src/script_interface/ObjectList.hpp
index 65e9332a8b6..72b7bb8f9b7 100644
--- a/src/script_interface/ObjectList.hpp
+++ b/src/script_interface/ObjectList.hpp
@@ -22,9 +22,9 @@
 #ifndef SCRIPT_INTERFACE_OBJECT_LIST_HPP
 #define SCRIPT_INTERFACE_OBJECT_LIST_HPP
 
+#include "script_interface/ObjectContainer.hpp"
 #include "script_interface/ScriptInterface.hpp"
 #include "script_interface/get_value.hpp"
-#include "script_interface/object_container_mpi_guard.hpp"
 
 #include <utils/serialization/pack.hpp>
 
@@ -35,20 +35,39 @@
 #include <vector>
 
 namespace ScriptInterface {
+
 /**
  * @brief Owning list of ObjectHandles
  * @tparam ManagedType Type of the managed objects, needs to be
- *         derived from ObjectHandle
+ *         derived from @ref ObjectHandle
  */
-template <typename ManagedType, class BaseType = ObjectHandle,
-          class =
-              std::enable_if_t<std::is_base_of_v<ObjectHandle, ManagedType>>>
-class ObjectList : public BaseType {
+template <typename ManagedType, class BaseType = ObjectHandle>
+class ObjectList : public ObjectContainer<ObjectList, ManagedType, BaseType> {
+public:
+  using Base = ObjectContainer<ObjectList, ManagedType, BaseType>;
+  using Base::add_parameters;
+
 private:
+  std::vector<std::shared_ptr<ManagedType>> m_elements;
+
   virtual void add_in_core(const std::shared_ptr<ManagedType> &obj_ptr) = 0;
   virtual void remove_in_core(const std::shared_ptr<ManagedType> &obj_ptr) = 0;
 
 public:
+  ObjectList() {
+    add_parameters({
+        {"_objects", AutoParameter::read_only,
+         [this]() { return make_vector_of_variants(m_elements); }},
+    });
+  }
+
+  void do_construct(VariantMap const &params) override {
+    m_elements = get_value_or<decltype(m_elements)>(params, "_objects", {});
+    for (auto const &object : m_elements) {
+      add_in_core(object);
+    }
+  }
+
   /**
    * @brief Add an element to the list.
    *
@@ -107,12 +126,7 @@ class ObjectList : public BaseType {
     }
 
     if (method == "get_elements") {
-      std::vector<Variant> ret;
-      ret.reserve(m_elements.size());
-      for (auto const &e : m_elements)
-        ret.emplace_back(e);
-
-      return ret;
+      return make_vector_of_variants(m_elements);
     }
 
     if (method == "clear") {
@@ -128,33 +142,8 @@ class ObjectList : public BaseType {
       return m_elements.empty();
     }
 
-    return BaseType::do_call_method(method, parameters);
+    return Base::do_call_method(method, parameters);
   }
-
-private:
-  std::string get_internal_state() const override {
-    object_container_mpi_guard(BaseType::name(), m_elements.size(),
-                               BaseType::context()->get_comm().size());
-
-    std::vector<std::string> object_states(m_elements.size());
-
-    boost::transform(m_elements, object_states.begin(),
-                     [](auto const &e) { return e->serialize(); });
-
-    return Utils::pack(object_states);
-  }
-
-  void set_internal_state(std::string const &state) override {
-    auto const object_states = Utils::unpack<std::vector<std::string>>(state);
-
-    for (auto const &packed_object : object_states) {
-      auto o = std::dynamic_pointer_cast<ManagedType>(
-          BaseType::deserialize(packed_object, *BaseType::context()));
-      add(std::move(o));
-    }
-  }
-
-  std::vector<std::shared_ptr<ManagedType>> m_elements;
 };
 } // Namespace ScriptInterface
 #endif
diff --git a/src/script_interface/tests/serialization_mpi_guard_test.cpp b/src/script_interface/tests/serialization_mpi_guard_test.cpp
index 72749046f97..7c9686a256c 100644
--- a/src/script_interface/tests/serialization_mpi_guard_test.cpp
+++ b/src/script_interface/tests/serialization_mpi_guard_test.cpp
@@ -23,7 +23,7 @@
 #include <boost/test/unit_test.hpp>
 
 #include "script_interface/GlobalContext.hpp"
-#include "script_interface/ObjectList.hpp"
+#include "script_interface/ObjectMap.hpp"
 
 #include <boost/mpi.hpp>
 
@@ -36,17 +36,16 @@
 using ScriptInterface::ObjectHandle;
 
 namespace Testing {
-struct ObjectContainer : ScriptInterface::ObjectList<ObjectHandle> {
-  std::vector<std::shared_ptr<ObjectHandle>> objects;
-
+class ObjectContainer : public ScriptInterface::ObjectMap<ObjectHandle> {
 private:
-  void add_in_core(std::shared_ptr<ObjectHandle> const &obj_ptr) override {
-    objects.push_back(obj_ptr);
+  int insert_in_core(std::shared_ptr<ObjectHandle> const &) override {
+    return 1;
   }
-  void remove_in_core(std::shared_ptr<ObjectHandle> const &obj_ptr) override {
-    objects.erase(std::remove(objects.begin(), objects.end(), obj_ptr),
-                  objects.end());
+  void insert_in_core(int const &,
+                      std::shared_ptr<ObjectHandle> const &ptr) override {
+    insert_in_core(ptr);
   }
+  void erase_in_core(int const &) override {}
 };
 } // namespace Testing
 
@@ -71,12 +70,12 @@ BOOST_AUTO_TEST_CASE(parallel_exception) {
     auto &list = dynamic_cast<Testing::ObjectContainer &>(*list_so);
     BOOST_CHECK_NO_THROW(list.serialize());
 
-    list.add(obj_ptr);
+    list.insert(0, obj_ptr);
     if (world.size() > 1) {
       BOOST_CHECK_EXCEPTION(list.serialize(), std::runtime_error, predicate);
     }
 
-    list.remove(obj_ptr);
+    list.erase(0);
     BOOST_CHECK_NO_THROW(list.serialize());
   } else {
     cb.loop();
diff --git a/testsuite/python/save_checkpoint.py b/testsuite/python/save_checkpoint.py
index 38b2b09df86..e7d3d07e210 100644
--- a/testsuite/python/save_checkpoint.py
+++ b/testsuite/python/save_checkpoint.py
@@ -64,8 +64,6 @@
 for filepath in path_cpt_root.iterdir():
     filepath.unlink(missing_ok=True)
 
-n_nodes = system.cell_system.get_state()["n_nodes"]
-
 # Lees-Edwards boundary conditions
 if 'INT.NPT' not in modes:
     protocol = espressomd.lees_edwards.LinearShear(
@@ -186,8 +184,7 @@
 union = espressomd.shapes.Union()
 union.add([espressomd.shapes.Wall(normal=[1., 0., 0.], dist=0.5),
            espressomd.shapes.Wall(normal=[0., 1., 0.], dist=1.5)])
-if n_nodes == 1:
-    system.constraints.add(shape=union, particle_type=2)
+system.constraints.add(shape=union, particle_type=2)
 if espressomd.has_features("ELECTROSTATICS"):
     system.constraints.add(espressomd.constraints.ElectricPlaneWave(
         E0=[1., -2., 3.], k=[-.1, .2, .3], omega=5., phi=1.4))
diff --git a/testsuite/python/test_checkpoint.py b/testsuite/python/test_checkpoint.py
index 4c99af5bd01..18e3088e050 100644
--- a/testsuite/python/test_checkpoint.py
+++ b/testsuite/python/test_checkpoint.py
@@ -55,7 +55,6 @@ class CheckpointTest(ut.TestCase):
         **config.get_checkpoint_params())
     checkpoint.load(0)
     path_cpt_root = pathlib.Path(checkpoint.checkpoint_dir)
-    n_nodes = system.cell_system.get_state()["n_nodes"]
 
     @classmethod
     def setUpClass(cls):
@@ -720,9 +719,7 @@ def check_lb_boundaries(self, remove_boundaries=False):
         np.testing.assert_equal(np.copy(lbf[:, :, :].boundary.astype(int)), 0)
 
     def test_constraints(self):
-        n_contraints = 7
-        if self.n_nodes == 1:
-            n_contraints += 1
+        n_contraints = 8
         if espressomd.has_features("ELECTROSTATICS"):
             n_contraints += 1
         self.assertEqual(len(system.constraints), n_contraints)
@@ -771,20 +768,19 @@ def test_constraints(self):
         np.testing.assert_allclose(np.copy(c[6].field), np.copy(ref_vec.field),
                                    atol=1e-10)
 
-        if self.n_nodes == 1:
-            union = c[7].shape
-            self.assertIsInstance(union, espressomd.shapes.Union)
-            self.assertEqual(c[7].particle_type, 2)
-            self.assertEqual(len(union), 2)
-            wall1, wall2 = union.call_method('get_elements')
-            self.assertIsInstance(wall1, espressomd.shapes.Wall)
-            self.assertIsInstance(wall2, espressomd.shapes.Wall)
-            np.testing.assert_allclose(np.copy(wall1.normal),
-                                       [1., 0., 0.], atol=1e-10)
-            np.testing.assert_allclose(np.copy(wall2.normal),
-                                       [0., 1., 0.], atol=1e-10)
-            np.testing.assert_allclose(wall1.dist, 0.5, atol=1e-10)
-            np.testing.assert_allclose(wall2.dist, 1.5, atol=1e-10)
+        union = c[7].shape
+        self.assertIsInstance(union, espressomd.shapes.Union)
+        self.assertEqual(c[7].particle_type, 2)
+        self.assertEqual(len(union), 2)
+        wall1, wall2 = union.call_method('get_elements')
+        self.assertIsInstance(wall1, espressomd.shapes.Wall)
+        self.assertIsInstance(wall2, espressomd.shapes.Wall)
+        np.testing.assert_allclose(np.copy(wall1.normal),
+                                   [1., 0., 0.], atol=1e-10)
+        np.testing.assert_allclose(np.copy(wall2.normal),
+                                   [0., 1., 0.], atol=1e-10)
+        np.testing.assert_allclose(wall1.dist, 0.5, atol=1e-10)
+        np.testing.assert_allclose(wall2.dist, 1.5, atol=1e-10)
 
         if espressomd.has_features("ELECTROSTATICS"):
             wave = c[n_contraints - 1]
@@ -795,6 +791,23 @@ def test_constraints(self):
             self.assertAlmostEqual(wave.omega, 5., delta=1E-10)
             self.assertAlmostEqual(wave.phi, 1.4, delta=1E-10)
 
+    @utx.skipIfMissingFeatures("WCA")
+    @ut.skipIf("INT.SDM" in modes, "Stokesian integrator not supported")
+    @ut.skipIf("INT.BD" in modes, "Brownian integrator not supported")
+    @ut.skipIf("INT.SD" in modes, "Steepest descent not supported")
+    def test_union(self):
+        # the union shape is an object list, and should be properly
+        # deserialized on all MPI ranks
+        system.non_bonded_inter[2, 6].wca.set_params(epsilon=1., sigma=1.)
+        p1 = system.part.add(pos=[1., 1.6, 0.], type=6)
+        p2 = system.part.add(pos=[system.box_l[0] - 1., 1.6, 0.], type=6)
+        system.integrator.run(0, recalc_forces=True)
+        np.testing.assert_allclose(p1.f, [0., 1e8, 0.], atol=1e-3)
+        np.testing.assert_allclose(p2.f, [0., 1e8, 0.], atol=1e-3)
+        p1.remove()
+        p2.remove()
+        system.non_bonded_inter[2, 6].reset()
+
 
 if __name__ == '__main__':
     config.bind_test_class(CheckpointTest)

From 5ab7ac292917a06b5a2278b046aa6c1ecb61bef0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-No=C3=ABl=20Grad?= <jgrad@icp.uni-stuttgart.de>
Date: Thu, 11 May 2023 12:35:04 +0200
Subject: [PATCH 2/2] script_interface: Rewrite ObjectMap as AutoParameters

---
 doc/sphinx/io.rst                             |  5 --
 src/python/espressomd/interactions.py         | 14 ++-
 src/python/espressomd/script_interface.pyx    | 36 --------
 src/script_interface/CMakeLists.txt           |  4 +-
 src/script_interface/ObjectMap.hpp            | 83 ++++++++---------
 .../interactions/BondedInteractions.hpp       | 21 +++--
 .../object_container_mpi_guard.cpp            | 38 --------
 .../object_container_mpi_guard.hpp            | 48 ----------
 src/script_interface/tests/CMakeLists.txt     |  3 -
 .../tests/serialization_mpi_guard_test.cpp    | 89 -------------------
 testsuite/python/bond_breakage.py             | 10 +--
 11 files changed, 76 insertions(+), 275 deletions(-)
 delete mode 100644 src/script_interface/object_container_mpi_guard.cpp
 delete mode 100644 src/script_interface/object_container_mpi_guard.hpp
 delete mode 100644 src/script_interface/tests/serialization_mpi_guard_test.cpp

diff --git a/doc/sphinx/io.rst b/doc/sphinx/io.rst
index 66f07f5b6ab..520b06b6fe6 100644
--- a/doc/sphinx/io.rst
+++ b/doc/sphinx/io.rst
@@ -111,11 +111,6 @@ Be aware of the following limitations:
   for a specific combination of features, please share your findings
   with the |es| community.
 
-* Checkpointing only supports recursion on the head node. It is therefore
-  impossible to checkpoint a :class:`espressomd.system.System` instance that
-  contains LB boundaries, constraint unions or auto-update accumulators when the
-  simulation is running with 2 or more MPI nodes.
-
 * The active actors, i.e., the content of ``system.actors``, are checkpointed.
   For lattice-Boltzmann fluids, this only includes the parameters such as the
   lattice constant (``agrid``). The actual flow field has to be saved
diff --git a/src/python/espressomd/interactions.py b/src/python/espressomd/interactions.py
index f6e9578cf80..c765f4bfea6 100644
--- a/src/python/espressomd/interactions.py
+++ b/src/python/espressomd/interactions.py
@@ -1546,8 +1546,6 @@ def add(self, *args):
         return bond_id
 
     def __getitem__(self, bond_id):
-        self._assert_key_type(bond_id)
-
         if self.call_method('has_bond', bond_id=bond_id):
             bond_obj = self.call_method('get_bond', bond_id=bond_id)
             bond_obj._bond_id = bond_id
@@ -1590,7 +1588,6 @@ def _insert_bond(self, bond_id, bond_obj):
             bond_id = self.call_method("insert", object=bond_obj)
         else:
             # Throw error if attempting to overwrite a bond of different type
-            self._assert_key_type(bond_id)
             if self.call_method("contains", key=bond_id):
                 old_type = self._bond_classes[
                     self.call_method("get_zero_based_type", bond_id=bond_id)]
@@ -1625,3 +1622,14 @@ def __getstate__(self):
     def __setstate__(self, params):
         for bond_id, (type_number, bond_params) in params.items():
             self[bond_id] = self._bond_classes[type_number](**bond_params)
+
+    def __reduce__(self):
+        so_callback, (so_name, so_bytestring) = super().__reduce__()
+        return (BondedInteractions._restore_object,
+                (so_callback, (so_name, so_bytestring), self.__getstate__()))
+
+    @classmethod
+    def _restore_object(cls, so_callback, so_callback_args, state):
+        so = so_callback(*so_callback_args)
+        so.__setstate__(state)
+        return so
diff --git a/src/python/espressomd/script_interface.pyx b/src/python/espressomd/script_interface.pyx
index 458d5eb1e61..39a2121c845 100644
--- a/src/python/espressomd/script_interface.pyx
+++ b/src/python/espressomd/script_interface.pyx
@@ -480,17 +480,6 @@ class ScriptObjectMap(ScriptInterfaceHelper):
 
     """
 
-    _key_type = int
-
-    def __init__(self, *args, **kwargs):
-        if args:
-            params, (_unpickle_so_class, (_so_name, bytestring)) = args
-            assert _so_name == self._so_name
-            self = _unpickle_so_class(_so_name, bytestring)
-            self.__setstate__(params)
-        else:
-            super().__init__(**kwargs)
-
     def remove(self, key):
         """
         Remove the element with the given key.
@@ -509,15 +498,12 @@ class ScriptObjectMap(ScriptInterfaceHelper):
         return self.call_method("size")
 
     def __getitem__(self, key):
-        self._assert_key_type(key)
         return self.call_method("get", key=key)
 
     def __setitem__(self, key, value):
-        self._assert_key_type(key)
         self.call_method("insert", key=key, object=value)
 
     def __delitem__(self, key):
-        self._assert_key_type(key)
         self.call_method("erase", key=key)
 
     def keys(self):
@@ -529,28 +515,6 @@ class ScriptObjectMap(ScriptInterfaceHelper):
     def items(self):
         for k in self.keys(): yield k, self[k]
 
-    def _assert_key_type(self, key):
-        if not utils.is_valid_type(key, self._key_type):
-            raise TypeError(f"Key has to be of type {self._key_type.__name__}")
-
-    @classmethod
-    def _restore_object(cls, so_callback, so_callback_args, state):
-        so = so_callback(*so_callback_args)
-        so.__setstate__(state)
-        return so
-
-    def __reduce__(self):
-        so_callback, (so_name, so_bytestring) = super().__reduce__()
-        return (ScriptObjectMap._restore_object,
-                (so_callback, (so_name, so_bytestring), self.__getstate__()))
-
-    def __getstate__(self):
-        return dict(self.items())
-
-    def __setstate__(self, params):
-        for key, val in params.items():
-            self[key] = val
-
 
 # Map from script object names to their corresponding python classes
 _python_class_by_so_name = {}
diff --git a/src/script_interface/CMakeLists.txt b/src/script_interface/CMakeLists.txt
index f53e6c85e88..13736ca4090 100644
--- a/src/script_interface/CMakeLists.txt
+++ b/src/script_interface/CMakeLists.txt
@@ -19,8 +19,8 @@
 
 add_library(
   espresso_script_interface SHARED
-  initialize.cpp ObjectHandle.cpp object_container_mpi_guard.cpp
-  GlobalContext.cpp ContextManager.cpp ParallelExceptionHandler.cpp)
+  initialize.cpp ObjectHandle.cpp GlobalContext.cpp ContextManager.cpp
+  ParallelExceptionHandler.cpp)
 add_library(espresso::script_interface ALIAS espresso_script_interface)
 set_target_properties(espresso_script_interface
                       PROPERTIES CXX_CLANG_TIDY "${ESPRESSO_CXX_CLANG_TIDY}")
diff --git a/src/script_interface/ObjectMap.hpp b/src/script_interface/ObjectMap.hpp
index ee763c4f9d7..d62e76b11fb 100644
--- a/src/script_interface/ObjectMap.hpp
+++ b/src/script_interface/ObjectMap.hpp
@@ -22,11 +22,10 @@
 #ifndef SCRIPT_INTERFACE_OBJECT_MAP_HPP
 #define SCRIPT_INTERFACE_OBJECT_MAP_HPP
 
+#include "script_interface/ObjectContainer.hpp"
 #include "script_interface/ScriptInterface.hpp"
+#include "script_interface/Variant.hpp"
 #include "script_interface/get_value.hpp"
-#include "script_interface/object_container_mpi_guard.hpp"
-
-#include <utils/serialization/pack.hpp>
 
 #include <memory>
 #include <string>
@@ -38,13 +37,18 @@ namespace ScriptInterface {
 /**
  * @brief Owning map of ObjectHandles
  * @tparam ManagedType Type of the managed objects, needs to be
- *         derived from ObjectHandle
+ *         derived from @ref ObjectHandle
  */
-template <
-    typename ManagedType, class BaseType = ObjectHandle, class KeyType = int,
-    class = std::enable_if_t<std::is_base_of_v<ObjectHandle, ManagedType>>>
-class ObjectMap : public BaseType {
+template <typename ManagedType, class BaseType = ObjectHandle,
+          class KeyType = int>
+class ObjectMap : public ObjectContainer<ObjectMap, ManagedType, BaseType> {
+public:
+  using Base = ObjectContainer<ObjectMap, ManagedType, BaseType>;
+  using Base::add_parameters;
+
 private:
+  std::unordered_map<KeyType, std::shared_ptr<ManagedType>> m_elements;
+
   virtual KeyType
   insert_in_core(std::shared_ptr<ManagedType> const &obj_ptr) = 0;
   virtual void insert_in_core(KeyType const &key,
@@ -52,6 +56,20 @@ class ObjectMap : public BaseType {
   virtual void erase_in_core(KeyType const &key) = 0;
 
 public:
+  ObjectMap() {
+    add_parameters({
+        {"_objects", AutoParameter::read_only,
+         [this]() { return make_unordered_map_of_variants(m_elements); }},
+    });
+  }
+
+  void do_construct(VariantMap const &params) override {
+    m_elements = get_value_or<decltype(m_elements)>(params, "_objects", {});
+    for (auto const &[key, element] : m_elements) {
+      insert_in_core(key, element);
+    }
+  }
+
   /**
    * @brief Add an element to the map.
    *
@@ -110,7 +128,7 @@ class ObjectMap : public BaseType {
           get_value<std::shared_ptr<ManagedType>>(parameters.at("object"));
 
       if (parameters.count("key")) {
-        auto key = get_value<KeyType>(parameters.at("key"));
+        auto const key = get_key(parameters.at("key"));
         insert(key, obj_ptr);
         return none;
       }
@@ -118,14 +136,13 @@ class ObjectMap : public BaseType {
     }
 
     if (method == "erase") {
-      auto key = get_value<KeyType>(parameters.at("key"));
-
+      auto const key = get_key(parameters.at("key"));
       erase(key);
       return none;
     }
 
     if (method == "get") {
-      auto key = get_value<KeyType>(parameters.at("key"));
+      auto const key = get_key(parameters.at("key"));
       return Variant{m_elements.at(key)};
     }
 
@@ -155,40 +172,26 @@ class ObjectMap : public BaseType {
     }
 
     if (method == "contains") {
-      return m_elements.find(get_value<KeyType>(parameters.at("key"))) !=
-             m_elements.end();
+      return m_elements.find(get_key(parameters.at("key"))) != m_elements.end();
     }
 
-    return BaseType::do_call_method(method, parameters);
+    return Base::do_call_method(method, parameters);
   }
 
-private:
-  std::string get_internal_state() const override {
-    object_container_mpi_guard(BaseType::name(), m_elements.size(),
-                               BaseType::context()->get_comm().size());
-
-    using packed_type = std::pair<KeyType, std::string>;
-    std::vector<packed_type> object_states(m_elements.size());
-
-    boost::transform(m_elements, object_states.begin(), [](auto const &kv) {
-      return std::make_pair(kv.first, kv.second->serialize());
-    });
-
-    return Utils::pack(object_states);
-  }
-
-  void set_internal_state(std::string const &state) override {
-    using packed_type = std::pair<KeyType, std::string>;
-    auto const object_states = Utils::unpack<std::vector<packed_type>>(state);
-
-    for (auto const &packed_object : object_states) {
-      auto o = std::dynamic_pointer_cast<ManagedType>(
-          BaseType::deserialize(packed_object.second, *BaseType::context()));
-      insert(packed_object.first, std::move(o));
+  KeyType get_key(Variant const &key) const {
+    try {
+      return get_value<KeyType>(key);
+    } catch (...) {
+      using namespace detail::demangle;
+      auto const actual = simplify_symbol_variant(key);
+      auto const target = simplify_symbol(static_cast<KeyType *>(nullptr));
+      if (Base::context()->is_head_node()) {
+        throw std::invalid_argument("Key has to be of type '" + target +
+                                    "', got type '" + actual + "'");
+      }
+      throw;
     }
   }
-
-  std::unordered_map<KeyType, std::shared_ptr<ManagedType>> m_elements;
 };
 } // Namespace ScriptInterface
 #endif
diff --git a/src/script_interface/interactions/BondedInteractions.hpp b/src/script_interface/interactions/BondedInteractions.hpp
index fe92ef1e196..92b65880354 100644
--- a/src/script_interface/interactions/BondedInteractions.hpp
+++ b/src/script_interface/interactions/BondedInteractions.hpp
@@ -29,6 +29,7 @@
 
 #include <cassert>
 #include <memory>
+#include <stdexcept>
 #include <string>
 #include <unordered_map>
 #include <utility>
@@ -44,6 +45,16 @@ class BondedInteractions : public ObjectMap<BondedInteraction> {
   using key_type = typename container_type::key_type;
   using mapped_type = typename container_type::mapped_type;
 
+  BondedInteractions() : ObjectMap<BondedInteraction>::ObjectMap() {
+    add_parameters({
+        {"_objects", AutoParameter::read_only,
+         []() {
+           // deactivate serialization (done at the Python level)
+           return make_unordered_map_of_variants(container_type{});
+         }},
+    });
+  }
+
   key_type insert_in_core(mapped_type const &obj_ptr) override {
     auto const key = ::bonded_ia_params.insert(obj_ptr->bonded_ia());
     m_bonds[key] = std::move(obj_ptr);
@@ -64,6 +75,7 @@ class BondedInteractions : public ObjectMap<BondedInteraction> {
     mpi_update_cell_system_ia_range_local();
   }
 
+protected:
   Variant do_call_method(std::string const &name,
                          VariantMap const &params) override {
     if (name == "get_size") {
@@ -78,12 +90,12 @@ class BondedInteractions : public ObjectMap<BondedInteraction> {
     }
 
     if (name == "has_bond") {
-      auto const bond_id = get_value<int>(params, "bond_id");
+      auto const bond_id = get_key(params.at("bond_id"));
       return {m_bonds.count(bond_id) != 0};
     }
 
     if (name == "get_bond") {
-      auto const bond_id = get_value<int>(params, "bond_id");
+      auto const bond_id = get_key(params.at("bond_id"));
       // core and script interface must agree
       assert(m_bonds.count(bond_id) == ::bonded_ia_params.count(bond_id));
       if (not context()->is_head_node())
@@ -97,7 +109,7 @@ class BondedInteractions : public ObjectMap<BondedInteraction> {
     }
 
     if (name == "get_zero_based_type") {
-      auto const bond_id = get_value<int>(params, "bond_id");
+      auto const bond_id = get_key(params.at("bond_id"));
       return ::bonded_ia_params.get_zero_based_type(bond_id);
     }
 
@@ -105,9 +117,6 @@ class BondedInteractions : public ObjectMap<BondedInteraction> {
   }
 
 private:
-  // disable serialization: pickling done by the python interface
-  std::string get_internal_state() const override { return {}; }
-  void set_internal_state(std::string const &state) override {}
   container_type m_bonds;
 };
 } // namespace Interactions
diff --git a/src/script_interface/object_container_mpi_guard.cpp b/src/script_interface/object_container_mpi_guard.cpp
deleted file mode 100644
index da62287b3f2..00000000000
--- a/src/script_interface/object_container_mpi_guard.cpp
+++ /dev/null
@@ -1,38 +0,0 @@
-/*
- * Copyright (C) 2021-2022 The ESPResSo project
- *
- * This file is part of ESPResSo.
- *
- * ESPResSo is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * ESPResSo is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-#include "script_interface/object_container_mpi_guard.hpp"
-
-#include <boost/mpi/communicator.hpp>
-#include <boost/utility/string_ref.hpp>
-
-#include <cstddef>
-#include <sstream>
-#include <stdexcept>
-
-void object_container_mpi_guard(boost::string_ref const &name,
-                                std::size_t n_elements, int world_size) {
-  if (world_size > 1 and n_elements) {
-    std::stringstream error_msg;
-    error_msg << "Non-empty object containers do not support checkpointing in "
-              << "MPI environments. Container " << name << " contains "
-              << n_elements << " elements.";
-    throw std::runtime_error(error_msg.str());
-  }
-}
diff --git a/src/script_interface/object_container_mpi_guard.hpp b/src/script_interface/object_container_mpi_guard.hpp
deleted file mode 100644
index bb9723c5e6f..00000000000
--- a/src/script_interface/object_container_mpi_guard.hpp
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright (C) 2021-2022 The ESPResSo project
- *
- * This file is part of ESPResSo.
- *
- * ESPResSo is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * ESPResSo is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef ESPRESSO_OBJECT_CONTAINER_MPI_GUARD_HPP
-#define ESPRESSO_OBJECT_CONTAINER_MPI_GUARD_HPP
-
-#include <boost/mpi/communicator.hpp>
-#include <boost/utility/string_ref.hpp>
-
-#include <cstddef>
-
-/**
- * @brief Prevent object container serialization.
- *
- * The @ref ScriptInterface::ObjectHandle framework doesn't support
- * recursive deserialization. When an object container such as
- * @ref ScriptInterface::ObjectList is deserialized, the contained
- * objects are deserialized on the head node only, which leads to
- * silent bugs in simulations.
- *
- * This function needs to be called from an object container
- * <tt>get_internal_state()</tt> method to throw a runtime error
- * when the container is not empty and the MPI world size is
- * greater than 1.
- *
- * @param name        Name of the object container
- * @param n_elements  Number of elements in the container
- * @param world_size  MPI world size
- */
-void object_container_mpi_guard(boost::string_ref const &name,
-                                std::size_t n_elements, int world_size);
-
-#endif
diff --git a/src/script_interface/tests/CMakeLists.txt b/src/script_interface/tests/CMakeLists.txt
index 35b14fed086..0fc25729ec1 100644
--- a/src/script_interface/tests/CMakeLists.txt
+++ b/src/script_interface/tests/CMakeLists.txt
@@ -47,9 +47,6 @@ unit_test(NAME ObjectList_test SRC ObjectList_test.cpp DEPENDS
           espresso::script_interface espresso::core Boost::mpi)
 unit_test(NAME ObjectMap_test SRC ObjectMap_test.cpp DEPENDS
           espresso::script_interface espresso::core Boost::mpi)
-unit_test(NAME serialization_mpi_guard_test SRC
-          serialization_mpi_guard_test.cpp DEPENDS espresso::script_interface
-          Boost::mpi MPI::MPI_CXX NUM_PROC 2)
 unit_test(NAME Accumulators_test SRC Accumulators_test.cpp DEPENDS
           espresso::script_interface espresso::core)
 unit_test(NAME Constraints_test SRC Constraints_test.cpp DEPENDS
diff --git a/src/script_interface/tests/serialization_mpi_guard_test.cpp b/src/script_interface/tests/serialization_mpi_guard_test.cpp
deleted file mode 100644
index 7c9686a256c..00000000000
--- a/src/script_interface/tests/serialization_mpi_guard_test.cpp
+++ /dev/null
@@ -1,89 +0,0 @@
-/*
- * Copyright (C) 2022 The ESPResSo project
- *
- * This file is part of ESPResSo.
- *
- * ESPResSo is free software: you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation, either version 3 of the License, or
- * (at your option) any later version.
- *
- * ESPResSo is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-#define BOOST_TEST_NO_MAIN
-#define BOOST_TEST_MODULE Object container MPI guard test
-#define BOOST_TEST_DYN_LINK
-#include <boost/test/unit_test.hpp>
-
-#include "script_interface/GlobalContext.hpp"
-#include "script_interface/ObjectMap.hpp"
-
-#include <boost/mpi.hpp>
-
-#include <algorithm>
-#include <memory>
-#include <stdexcept>
-#include <string>
-#include <vector>
-
-using ScriptInterface::ObjectHandle;
-
-namespace Testing {
-class ObjectContainer : public ScriptInterface::ObjectMap<ObjectHandle> {
-private:
-  int insert_in_core(std::shared_ptr<ObjectHandle> const &) override {
-    return 1;
-  }
-  void insert_in_core(int const &,
-                      std::shared_ptr<ObjectHandle> const &ptr) override {
-    insert_in_core(ptr);
-  }
-  void erase_in_core(int const &) override {}
-};
-} // namespace Testing
-
-BOOST_AUTO_TEST_CASE(parallel_exception) {
-  boost::mpi::communicator world;
-  Utils::Factory<ObjectHandle> factory;
-  factory.register_new<Testing::ObjectContainer>("ObjectContainer");
-  Communication::MpiCallbacks cb{world};
-  auto ctx = std::make_shared<ScriptInterface::GlobalContext>(
-      cb, std::make_shared<ScriptInterface::LocalContext>(factory, world));
-
-  if (world.rank() == 0) {
-    auto const obj_ptr = std::make_shared<ScriptInterface::ObjectHandle>();
-    auto const predicate = [](std::exception const &ex) {
-      std::string message =
-          "Non-empty object containers do not support checkpointing in MPI "
-          "environments. Container ObjectContainer contains 1 elements.";
-      return ex.what() == message;
-    };
-
-    auto list_so = ctx->make_shared("ObjectContainer", {});
-    auto &list = dynamic_cast<Testing::ObjectContainer &>(*list_so);
-    BOOST_CHECK_NO_THROW(list.serialize());
-
-    list.insert(0, obj_ptr);
-    if (world.size() > 1) {
-      BOOST_CHECK_EXCEPTION(list.serialize(), std::runtime_error, predicate);
-    }
-
-    list.erase(0);
-    BOOST_CHECK_NO_THROW(list.serialize());
-  } else {
-    cb.loop();
-  }
-}
-
-int main(int argc, char **argv) {
-  boost::mpi::environment mpi_env(argc, argv);
-
-  return boost::unit_test::unit_test_main(init_unit_test, argc, argv);
-}
diff --git a/testsuite/python/bond_breakage.py b/testsuite/python/bond_breakage.py
index 9a374c40c91..c0565641d8a 100644
--- a/testsuite/python/bond_breakage.py
+++ b/testsuite/python/bond_breakage.py
@@ -84,12 +84,12 @@ def test_00_interface(self):
         self.system.bond_breakage.clear()
         self.assertEqual(len(self.system.bond_breakage), 0)
         self.assertEqual(self.system.bond_breakage.keys(), [])
-        with self.assertRaisesRegex(TypeError, "Key has to be of type int"):
+        with self.assertRaisesRegex(ValueError, "Key has to be of type 'int'"):
             self.system.bond_breakage[None]
-        with self.assertRaisesRegex(TypeError, "Key has to be of type int"):
-            self.system.bond_breakage[None] = None
-        with self.assertRaisesRegex(TypeError, "Key has to be of type int"):
-            self.system.bond_breakage.remove(None)
+        with self.assertRaisesRegex(ValueError, "Key has to be of type 'int'"):
+            self.system.bond_breakage[None] = spec2
+        with self.assertRaisesRegex(ValueError, "Key has to be of type 'int', got type 'double'"):
+            self.system.bond_breakage.remove(1.)
         with self.assertRaisesRegex(ValueError, "Bond needs to be added to the system first"):
             self.system.bond_breakage[HarmonicBond(k=1, r_0=0)]
         with self.assertRaisesRegex(RuntimeError, "Inserting breakage spec without a bond type is not permitted"):