Make sure CPU frequency is initialised once (per rank), allow user to define...

Make sure CPU frequency is initialised once (per rank), allow user to define it and report the frequency used

examples/main.c

@@ -77,6 +77,7 @@ int main(int argc, char *argv[]) {
   int nr_nodes = 1, myrank = 0;
   FILE *file_thread;
   int with_outputs = 1;
+  unsigned long long cpufreq = 0;
 
 #ifdef WITH_MPI
   struct partition initial_partition;
@@ -149,7 +150,7 @@ int main(int argc, char *argv[]) {
   bzero(&s, sizeof(struct space));
 
   /* Parse the options */
-  while ((c = getopt(argc, argv, "a:c:d:e:f:m:oP:q:R:s:t:w:y:z:")) != -1)
+  while ((c = getopt(argc, argv, "a:c:d:e:f:h:m:oP:q:R:s:t:w:y:z:")) != -1)
     switch (c) {
       case 'a':
         if (sscanf(optarg, "%lf", &scaling) != 1)
@@ -178,6 +179,12 @@ int main(int argc, char *argv[]) {
       case 'f':
         if (!strcpy(ICfileName, optarg)) error("Error parsing IC file name.");
         break;
+      case 'h':
+        if (sscanf(optarg, "%llu", &cpufreq) != 1)
+          error("Error parsing CPU frequency.");
+        if (myrank == 0) message("CPU frequency set to %llu.", cpufreq);
+        fflush(stdout);
+        break;
       case 'm':
         if (sscanf(optarg, "%lf", &h_max) != 1) error("Error parsing h_max.");
         if (myrank == 0) message("maximum h set to %e.", h_max);
@@ -318,6 +325,12 @@ int main(int argc, char *argv[]) {
             aFactor(&us, UNIT_CONV_ENTROPY), hFactor(&us, UNIT_CONV_ENTROPY));
   }
 
+  /* Initialize CPU frequency. */
+  clocks_set_cpufreq(cpufreq);
+  cpufreq = clocks_get_cpufreq();
+  if (myrank == 0)
+      message("CPU frequency used for tick conversion: %llu Hz", cpufreq);
+
   /* Check we have sensible time step bounds */
   if (dt_min > dt_max)
     error("Minimal time step size must be large than maximal time step size ");