Perform end of simulation broadcasts from C++

src/simulation.cpp

@@ -4,6 +4,12 @@
 #include "openmc/message_passing.h"
 #include "openmc/settings.h"
 
+#ifdef OPENMC_MPI
+#include <mpi.h>
+#endif
+
+#include <algorithm>
+
 // OPENMC_RUN encompasses all the main logic where iterations are performed
 // over the batches, generations, and histories in a fixed source or k-eigenvalue
 // calculation.
@@ -98,4 +104,46 @@ void calculate_work()
   }
 }
 
+#ifdef OPENMC_MPI
+void broadcast_results() {
+    // Broadcast tally results so that each process has access to results
+  double* buffer;
+  if (n_tallies > 0) {
+    for (int i=1; i <= n_tallies; ++i) {
+      // Create a new datatype that consists of all values for a given filter
+      // bin and then use that to broadcast. This is done to minimize the
+      // chance of the 'count' argument of MPI_BCAST exceeding 2**31
+      int shape[3];
+      openmc_tally_results(i, &buffer, shape);
+
+      int n = shape[0];
+      int count_per_filter = shape[1] * shape[2];
+      MPI_Datatype result_block;
+      MPI_Type_contiguous(count_per_filter, MPI_DOUBLE, &result_block);
+      MPI_Type_commit(&result_block);
+      MPI_Bcast(buffer, n, result_block, 0, mpi::intracomm);
+      MPI_Type_free(&result_block);
+    }
+  }
+
+  // Also broadcast global tally results
+  openmc_global_tallies(&buffer);
+  MPI_Bcast(buffer, 4, MPI_DOUBLE, 0, mpi::intracomm);
+
+  // These guys are needed so that non-master processes can calculate the
+  // combined estimate of k-effective
+  double temp[] {simulation::k_col_abs, simulation::k_col_tra,
+    simulation::k_abs_tra};
+  MPI_Bcast(temp, 3, MPI_DOUBLE, 0, mpi::intracomm);
+  simulation::k_col_abs = temp[0];
+  simulation::k_col_tra = temp[1];
+  simulation::k_abs_tra = temp[2];
+}
+
+void broadcast_triggers()
+{
+  MPI_Bcast(&simulation::satisfy_triggers, 1, MPI_C_BOOL, 0, mpi::intracomm);
+}
+#endif
+
 } // namespace openmc