Write separate track files for multiple MPI ranks

docs/source/usersguide/scripts.rst

@@ -114,6 +114,17 @@ tallies. The path to the statepoint file can be provided as an optional arugment
 
 .. _scripts_track:
 
+------------------------
+``openmc-track-combine``
+------------------------
+
+This script combines multiple HDF5 :ref:`particle track files
+<usersguide_track>` into a single HDF5 particle track file. The filenames of the
+particle track files should be given as posititional arguments. The output
+filename can also be changed with the ``-o`` flag:
+
+-o OUT, --out OUT    Output HDF5 particle track file
+
 -----------------------
 ``openmc-track-to-vtk``
 -----------------------

scripts/openmc-track-combine

@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+
+"""Combine multiple HDF5 particle track files.
+
+"""
+
+import argparse
+
+import h5py
+
+
+def main():
+    # Parse command-line arguments
+    parser = argparse.ArgumentParser(
+        description='Combine particle track files into a single .h5 file.')
+    parser.add_argument('input', metavar='IN', nargs='+',
+                        help='Input HDF5 particle track filename(s).')
+    parser.add_argument('-o', '--out', metavar='OUT', default='tracks.h5',
+                        help='Output HDF5 particle track file.')
+
+    args = parser.parse_args()
+
+    with h5py.File(args.out, 'w') as h5_out:
+        for i, fname in enumerate(args.input):
+            with h5py.File(fname, 'r') as h5_in:
+                # Copy file attributes for first file
+                if i == 0:
+                    h5_out.attrs['filetype'] = h5_in.attrs['filetype']
+                    h5_out.attrs['version'] = h5_in.attrs['version']
+
+                # Copy each 'track_*' dataset from input file
+                for dset in h5_in:
+                    h5_in.copy(dset, h5_out)
+
+
+if __name__ == '__main__':
+    main()

src/track_output.cpp

@@ -2,6 +2,7 @@
 
 #include "openmc/constants.h"
 #include "openmc/hdf5_interface.h"
+#include "openmc/message_passing.h"
 #include "openmc/position.h"
 #include "openmc/settings.h"
 #include "openmc/simulation.h"
@@ -40,8 +41,18 @@ void write_particle_track(Particle& p)
 
 void open_track_file()
 {
-  // Open file and write filetype/version
+  // Open file and write filetype/version -- when MPI is enabled and there is
+  // more than one rank, each rank writes its own file
+#ifdef OPENMC_MPI
+  std::string filename;
+  if (mpi::n_procs > 1) {
+    filename = fmt::format("{}tracks_p{}.h5", settings::path_output, mpi::rank);
+  } else {
+    filename = fmt::format("{}tracks.h5", settings::path_output);
+  }
+#else
   std::string filename = fmt::format("{}tracks.h5", settings::path_output);
+#endif
   track_file = file_open(filename, 'w');
   write_attribute(track_file, "filetype", "track");
   write_attribute(track_file, "version", VERSION_TRACK);