4 files changed, 147 insertions, 0 deletions
diff --git a/Source/ablastr/parallelization/CMakeLists.txt b/Source/ablastr/parallelization/CMakeLists.txt
new file mode 100644
index 000000000..a6957d4d5
--- /dev/null
+++ b/Source/ablastr/parallelization/CMakeLists.txt
@@ -0,0 +1,7 @@
+foreach(D IN LISTS WarpX_DIMS)
+    warpx_set_suffix_dims(SD ${D})
+    target_sources(ablastr_${SD}
+      PRIVATE
+        MPIInitHelpers.cpp
+    )
+endforeach()
diff --git a/Source/ablastr/parallelization/MPIInitHelpers.H b/Source/ablastr/parallelization/MPIInitHelpers.H
new file mode 100644
index 000000000..6b9bdfa47
--- /dev/null
+++ b/Source/ablastr/parallelization/MPIInitHelpers.H
@@ -0,0 +1,45 @@
+/* Copyright 2020 Axel Huebl
+ *
+ * This file is part of ABLASTR.
+ *
+ * License: BSD-3-Clause-LBNL
+ */
+#ifndef ABLASTR_MPI_INIT_HELPERS_H_
+#define ABLASTR_MPI_INIT_HELPERS_H_
+
+#include <utility>
+
+namespace ablastr::parallelization
+{
+    /** Return the required MPI threading
+     *
+     * @return the MPI_THREAD_* level required for MPI_Init_thread
+     */
+    int
+    mpi_thread_required ();
+
+    /** Initialize MPI
+     *
+     * @return pair(required, provided) of MPI thread level from MPI_Init_thread
+     */
+    std::pair< int, int >
+    mpi_init (int argc, char* argv[]);
+
+    /** Finalize MPI
+     *
+     * This function is simply a wrapper around MPI_Finalize(). It is a no-op if
+     * ABLASTR is compiled without MPI support.
+     */
+    void
+    mpi_finalize ();
+
+    /** Check if the requested MPI thread level is valid
+     *
+     * Prints warnings and notes otherwise.
+     */
+    void
+    check_mpi_thread_level ();
+
+} // namespace ablastr::parallelization
+
+#endif // ABLASTR_MPI_INIT_HELPERS_H_
diff --git a/Source/ablastr/parallelization/MPIInitHelpers.cpp b/Source/ablastr/parallelization/MPIInitHelpers.cpp
new file mode 100644
index 000000000..cdf458213
--- /dev/null
+++ b/Source/ablastr/parallelization/MPIInitHelpers.cpp
@@ -0,0 +1,93 @@
+/* Copyright 2020 Axel Huebl
+ *
+ * This file is part of ABLASTR.
+ *
+ * License: BSD-3-Clause-LBNL
+ */
+#include "MPIInitHelpers.H"
+
+#include <ablastr/warn_manager/WarnManager.H>
+
+#include <AMReX_Config.H>
+#include <AMReX_ParallelDescriptor.H>
+#include <AMReX_Print.H>
+
+#if defined(AMREX_USE_MPI)
+#   include <mpi.h>
+#endif
+
+#include <string>
+#include <utility>
+#include <sstream>
+
+namespace ablastr::parallelization
+{
+    int
+    mpi_thread_required ()
+    {
+        int thread_required = -1;
+#ifdef AMREX_USE_MPI
+        thread_required = MPI_THREAD_SINGLE;  // equiv. to MPI_Init
+#   ifdef AMREX_USE_OMP
+        thread_required = MPI_THREAD_FUNNELED;
+#   endif
+#   ifdef AMREX_MPI_THREAD_MULTIPLE  // i.e. for async_io
+        thread_required = MPI_THREAD_MULTIPLE;
+#   endif
+#endif
+        return thread_required;
+    }
+
+    std::pair< int, int >
+    mpi_init (int argc, char* argv[])
+    {
+        const int thread_required = mpi_thread_required();
+#ifdef AMREX_USE_MPI
+        int thread_provided = -1;
+        MPI_Init_thread(&argc, &argv, thread_required, &thread_provided);
+#else
+        amrex::ignore_unused(argc, argv);
+        const int thread_provided = -1;
+#endif
+        return std::make_pair(thread_required, thread_provided);
+    }
+
+
+    void
+    mpi_finalize ()
+    {
+#ifdef AMREX_USE_MPI
+        MPI_Finalize();
+#endif
+    }
+
+    void
+    check_mpi_thread_level ()
+    {
+#ifdef AMREX_USE_MPI
+        const int thread_required = mpi_thread_required();
+        int thread_provided = -1;
+        MPI_Query_thread(&thread_provided);
+        auto mtn = amrex::ParallelDescriptor::mpi_level_to_string;
+
+        std::stringstream ss;
+        if( thread_provided < thread_required ){
+            ss << "WARNING: Provided MPI thread safety level ("
+                           << mtn(thread_provided) << ") is LOWER than requested "
+                           << mtn(thread_required) << "). This might lead to undefined "
+                           << "results in asynchronous operations (e.g. async_io).";
+            ablastr::warn_manager::WMRecordWarning(
+                    "MPI", ss.str(), ablastr::warn_manager::WarnPriority::high);
+        }
+        if( thread_provided > thread_required ){
+            ss << "NOTE: Provided MPI thread safety level ("
+                           << mtn(thread_provided) << ") is stricter than requested "
+                           << mtn(thread_required) << "). This might reduce multi-node "
+                           << "communication performance.";
+            ablastr::warn_manager::WMRecordWarning(
+                    "MPI", ss.str());
+        }
+#endif
+    }
+
+} // namespace ablastr::parallelization
diff --git a/Source/ablastr/parallelization/Make.package b/Source/ablastr/parallelization/Make.package
index 9b248b7fa..a70a8a61e 100644
--- a/Source/ablastr/parallelization/Make.package
+++ b/Source/ablastr/parallelization/Make.package
@@ -1 +1,3 @@
+CEXE_sources += MPIInitHelpers.cpp
+
 VPATH_LOCATIONS   += $(WARPX_HOME)/Source/ablastr/parallelization