config: Add get_rank() helper.

Author: memmett

include/pfasst/config.hpp

@@ -26,6 +26,30 @@ namespace pfasst
    */
   namespace config
   {
+    /**
+     * Get MPI rank during initialization.
+     *
+     * When running without MPI (ie, without using mpirun/mpiexec), returns 0.  When running with
+     * MPI, returns the MPI rank.
+     *
+     * If the user is running with MPI and MPI_Init hasn't been called yet, this will return 0.  I
+     * hope this is rare.
+     */
+    int get_rank()
+    {
+#ifdef WITH_MPI
+      int initialized = 0, rank = 0;
+      // if we're not running under "mpirun/mpiexec", just assume rank 0.
+      MPI_Initialized(&initialized);
+      if (initialized) {
+        MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+      }
+      return rank;
+#else
+      return 0;
+#endif
+    }
+
     /**
      * Runtime config options provider.
      *
@@ -76,7 +100,7 @@ namespace pfasst
          * @param[in] option Name of the command line parameter.
          *   It is possible to specify a long and optional short option name by comma-separation.
          *   Short option names are identified by being only a single character.
-         *   They are automatically parsed as '`-[SHORT]`' by `boost::program_options` in contrast 
+         *   They are automatically parsed as '`-[SHORT]`' by `boost::program_options` in contrast
          *   to '`--[LONG]`'.
          * @param[in] help help text to be displayed in the help and usage information
          */
@@ -90,7 +114,7 @@ namespace pfasst
          * @param[in] option Name of the command line parameter.
          *   It is possible to specify a long and optional short option name by comma-separation.
          *   Short option names are identified by being only a single character.
-         *   They are automatically parsed as '`-[SHORT]`' by `boost::program_options` in contrast 
+         *   They are automatically parsed as '`-[SHORT]`' by `boost::program_options` in contrast
          *   to '`--[LONG]`'.
          * @param[in] help help text to be displayed in the help and usage information
          *
@@ -193,21 +217,11 @@ namespace pfasst
       po::store(parsed, options::get_instance().get_variables_map());
       po::notify(options::get_instance().get_variables_map());
 
-#ifdef WITH_MPI
-      int initialized = 0;
-      MPI_Initialized(&initialized);
-      assert((bool)initialized);
-      int rank = 0;
-      MPI_Comm_rank(MPI_COMM_WORLD, &rank);
-#endif
       if (options::get_instance().get_variables_map().count("help")) {
-#ifdef WITH_MPI
-        if (rank == 0) {
-#endif
+        if (get_rank() == 0) {
           cout << print_help() << endl;
-#ifdef WITH_MPI
         }
-#endif
+
         if (exit_on_help) {
 #ifdef WITH_MPI
           MPI_Finalize();
@@ -263,7 +277,7 @@ namespace pfasst
       options::add_option<double>("Duration", "tend", "final time of simulation");
       options::add_option<size_t>("Duration", "num_steps", "number time steps");
       options::add_option<size_t>("Duration", "num_iter", "number of iterations");
-      
+
       options::add_option<size_t>("Quadrature", "num_nodes", "number of quadrature nodes");
 
       options::add_option<double>("Tolerances", "abs_res_tol", "absolute residual tolerance");

include/pfasst/logging.hpp

@@ -166,7 +166,7 @@ namespace pfasst
    *   - `VLOG` - the verbose logging levels are used as follows:
    *     - 0 to 8
    *     - 9 for function enter and exit messages (cfg. @ref VLOG_FUNC_START and @ref VLOG_FUNC_END)
-   * 
+   *
    * @see [easylogging++](https://github.com/easylogging/easyloggingpp)
    */
   namespace log
@@ -213,12 +213,7 @@ namespace pfasst
       const string POSITION = "%fbase:%line";
       const string MESSAGE = "%msg";
 #ifdef WITH_MPI
-      int initialized = 0;
-      MPI_Initialized(&initialized);
-      assert((bool)initialized);
-      int rank = 0;
-      MPI_Comm_rank(MPI_COMM_WORLD, &rank);
-
+      const int rank = pfasst::config::get_rank();
       ostringstream frmter;
       frmter << std::setw(3) << rank;
       const string MPI_RANK = ", rank " + frmter.str();
@@ -290,11 +285,7 @@ namespace pfasst
         defaultConf.setGlobally(el::ConfigurationType::ToStandardOutput, "false");
       }
 #ifdef WITH_MPI
-      int initialized = 0;
-      MPI_Initialized(&initialized);
-      assert((bool)initialized);
-      int rank = 0;
-      MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+      int rank = pfasst::config::get_rank();
       defaultConf.setGlobally(el::ConfigurationType::ToFile, "true");
       defaultConf.setGlobally(el::ConfigurationType::Filename,
                               string("mpi_run_") + to_string(rank) + string(".log"));