Both MPI and non MPI versions are working with LAMMPS

bin/tadah_cli.cpp

@@ -314,6 +314,22 @@ void TadahCLI::subcommand_hpo(
   int ncpu=1;
   MPI_Comm_size(MPI_COMM_WORLD, &ncpu);
   MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+
+  // Create a communicator for LAMMPS
+  MPI_Group world_group;
+  MPI_Comm_group(MPI_COMM_WORLD, &world_group);
+
+  std::vector<int> ranks;
+  ranks.push_back(0); // for now we use root to run LAMMPS
+                      // long term we want to distribute
+                      // work among available workers
+
+  MPI_Group lmp_group;
+  MPI_Group_incl(world_group, ranks.size(), ranks.data(), &lmp_group);
+
+  MPI_Comm lmp_comm;
+  MPI_Comm_create(MPI_COMM_WORLD, lmp_group, &lmp_comm);
+
   if (rank==0) {
     if (ncpu<2) {
       std::cout << "Minimum number of cpus for an mpi version is 2" << std::endl;
@@ -321,7 +337,11 @@ void TadahCLI::subcommand_hpo(
     }
     if (is_verbose()) std::cout << "Optimising HPs..." << std::endl;
     CLI::Timer timer_tot {"HPO", CLI::Timer::Big};
-    hpo_run(config, target_file, validation_file);
+    hpo_run(config, target_file, validation_file, lmp_comm);
+
+    // shut all workers
+    int cont=0;
+    MPI_Bcast(&cont, 1, MPI_INT, 0, MPI_COMM_WORLD);
     if (is_verbose()) std::cout << timer_tot.to_string() << std::endl;
   }
   else { // WORKER
@@ -364,10 +384,15 @@ void TadahCLI::subcommand_hpo(
       WORKER.solve();
     }
   }
+  // Free the communicator and groups when done
+  //MPI_Comm_free(&lmp_comm);
+  MPI_Group_free(&world_group);
+  MPI_Group_free(&lmp_group);
 #else
   CLI::Timer timer_tot {"HPO", CLI::Timer::Big};
   if (is_verbose()) std::cout << "Optimising HPs..." << std::endl;
-  hpo_run(config, target_file, validation_file);
+  int dummy_comm=0;
+  hpo_run(config, target_file, validation_file, dummy_comm);
   if (is_verbose()) std::cout << timer_tot.to_string() << std::endl;
 #endif