refined statistics calculation

cellular_automaton/wireworld_c/main.c

@@ -16,6 +16,8 @@ void read_input(const conf_t *c, world_t *world);
 
 void iterate(const conf_t *c, world_t *world);
 
+void print_avg_timings(const conf_t *c, double total_time, double sim_time, double io_time);
+
 int main(int argc, char* argv[])
 {
    conf_t config;
@@ -140,12 +142,41 @@ void iterate(const conf_t *c, world_t *world)
    }
    total_time += MPI_Wtime();
 
-   if(info_enabled(c)) printf(
-      "\nStatistics:\n"
-      " * Generations per second:  %.0f\n"
-      " * Net simulation time (s): %f\n"
-      " * Net I/O time (s):        %f\n"
-      " * Total time (s):          %f\n\n",
-      g / sim_time, sim_time, io_time, total_time
+   print_avg_timings(c, total_time, sim_time, io_time);
+}
+
+void print_avg_timings(const conf_t *c, double total_time, double sim_time, double io_time)
+{
+   const int root = 0;
+   const size_t total_generations = c->n_iterations * c->n_generations_per_iteration;
+   int rank, nprocs;
+   double times[] = {total_time, sim_time, io_time};
+   void *sendbuf, *recvbuf;
+
+   MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+   MPI_Comm_size(MPI_COMM_WORLD, &nprocs);
+
+   sendbuf = rank == root ? MPI_IN_PLACE : times;
+   recvbuf = rank == root ? times        : NULL;
+
+   MPI_Reduce(
+      sendbuf, recvbuf, 3, MPI_DOUBLE,
+      MPI_SUM, root, MPI_COMM_WORLD
    );
+
+   if(info_enabled(c)) {
+      total_time = times[0] / nprocs;
+      sim_time =   times[1] / nprocs;
+      io_time =    times[2] / nprocs;
+
+      printf(
+         "\nStatistics:\n"
+         " * Generations per second:  %.0f\n"
+         " * Net simulation time (s): %f\n"
+         " * Net I/O time (s):        %f\n"
+         " * Total time (s):          %f\n\n",
+         total_generations / sim_time, sim_time, io_time, total_time
+      );
+   }
 }
+