diff --git a/src/AMSlib/wf/workflow.hpp b/src/AMSlib/wf/workflow.hpp
index 8310896..99d33ec 100644
--- a/src/AMSlib/wf/workflow.hpp
+++ b/src/AMSlib/wf/workflow.hpp
@@ -73,7 +73,7 @@ class AMSWorkflow
   std::shared_ptr<ams::db::BaseDB> DB;
 
   /** @brief The process id. For MPI runs this is the rank */
-  const int rId;
+  int rId;
 
   /** @brief The total number of processes participating in the simulation
    * (world_size for MPI) */
@@ -247,7 +247,17 @@ class AMSWorkflow
   void set_physics(AMSPhysicFn _AppCall) { AppCall = _AppCall; }
 
 #ifdef __ENABLE_MPI__
-  void set_communicator(MPI_Comm communicator) { comm = communicator; }
+  void set_communicator(MPI_Comm communicator) {
+    comm = communicator;
+
+    if (comm == MPI_COMM_NULL) {
+      rId = 0;
+      wSize = 1;
+    } else {
+      MPI_Comm_rank(comm, &rId);
+      MPI_Comm_size(comm, &wSize);
+    }
+  }
 #endif
 
   void set_exec_policy(AMSExecPolicy policy) { ePolicy = policy; }
diff --git a/tests/AMSlib/ams_ete.cpp b/tests/AMSlib/ams_ete.cpp
index 7c2578d..807730d 100644
--- a/tests/AMSlib/ams_ete.cpp
+++ b/tests/AMSlib/ams_ete.cpp
@@ -177,36 +177,49 @@ int main(int argc, char **argv)
   AMSCAbstrModel model_descr = AMSRegisterAbstractModel(
       "test", uq_policy, threshold, model_path, nullptr, "test", -1);
 
-  int process_id = 0;
-  int world_size = 1;
-
-#ifdef __ENABLE_MPI__
-  if (use_mpi) {
-    MPI_Comm_rank(MPI_COMM_WORLD, &process_id);
-    MPI_Comm_size(MPI_COMM_WORLD, &world_size);
-  }
-#endif // __ENABLE_MPI__
-
-
   if (data_type == AMSDType::AMS_SINGLE) {
     Problem<float> prob(num_inputs, num_outputs);
 
-    AMSExecutor wf = AMSCreateExecutor(model_descr,
-                                       AMSDType::AMS_SINGLE,
-                                       resource,
-                                       (AMSPhysicFn)callBackSingle,
-                                       process_id,
-                                       world_size);
+// TODO: I do not think we should pass the process id and world size here.
+// It should be obtained from the communicator passed.
+    AMSExecutor wf =
+#ifdef __ENABLE_MPI__
+      use_mpi?
+        AMSCreateDistributedExecutor(model_descr,
+                                     AMSDType::AMS_SINGLE,
+                                     resource,
+                                     (AMSPhysicFn)callBackSingle,
+                                     MPI_COMM_WORLD,
+                                     0,
+                                     1) :
+#endif // __ENABLE_MPI__
+        AMSCreateExecutor(model_descr,
+                          AMSDType::AMS_SINGLE,
+                          resource,
+                          (AMSPhysicFn)callBackSingle,
+                          0,
+                          1);
 
     prob.ams_run(wf, resource, num_iterations, avg_elements);
   } else {
     Problem<double> prob(num_inputs, num_outputs);
-    AMSExecutor wf = AMSCreateExecutor(model_descr,
-                                       AMSDType::AMS_DOUBLE,
-                                       resource,
-                                       (AMSPhysicFn)callBackDouble,
-                                       process_id,
-                                       world_size);
+    AMSExecutor wf =
+#ifdef __ENABLE_MPI__
+      use_mpi?
+        AMSCreateDistributedExecutor(model_descr,
+                                     AMSDType::AMS_DOUBLE,
+                                     resource,
+                                     (AMSPhysicFn)callBackDouble,
+                                     MPI_COMM_WORLD,
+                                     0,
+                                     1) :
+#endif // __ENABLE_MPI__
+        AMSCreateExecutor(model_descr,
+                          AMSDType::AMS_DOUBLE,
+                          resource,
+                          (AMSPhysicFn)callBackDouble,
+                          0,
+                          1);
     prob.ams_run(wf, resource, num_iterations, avg_elements);
   }