Let user specify the start-time of the program

core/reactor.c

@@ -328,8 +328,9 @@ int lf_reactor_c_main(int argc, const char* argv[]) {
 
     LF_PRINT_DEBUG("Initializing.");
     initialize_global();
-    // Set start time
-    start_time = lf_time_physical();
+    // Set the start time of the program (if it is not set from the command line). Possibly wait for
+    // it to arrive also.
+    _lf_set_and_wait_for_start_time();
 #ifndef FEDERATED
     lf_tracing_set_start_time(start_time);
 #endif

core/reactor_common.c

@@ -42,6 +42,9 @@
 // Global variable defined in tag.c:
 extern instant_t start_time;
 
+// Whether the start time of the program is decided by the user via a command line argument.
+bool start_time_specified = false;
+
 #if !defined NDEBUG
 // Global variable defined in lf_token.c:
 extern int _lf_count_payload_allocations;
@@ -882,6 +885,12 @@ void usage(int argc, const char* argv[]) {
   printf("   Executed in <n> threads if possible (optional feature).\n\n");
   printf("  -i, --id <n>\n");
   printf("   The ID of the federation that this reactor will join.\n\n");
+  printf("  -s, --start-time <time-point> <units> \n");
+  printf("   The logical start time of the program, expressed as an absolute time point\n");
+  printf("   which is the duration since the epoch of the underlying system clock.\n");
+  printf("   The units are nsec, usec, msec, sec, minute, hour, day, week or the plurals of those.\n");
+  printf("   On linux, to compute a start time of 2 minutes into the future, expressed in seconds, do:\n");
+  printf("     `date -d \"2 minutes\" +%%s`.\n\n");
 #ifdef FEDERATED
   printf("  -r, --rti <n>\n");
   printf("   The address of the RTI, which can be in the form of user@host:port or ip:port.\n\n");
@@ -901,6 +910,43 @@ void usage(int argc, const char* argv[]) {
 int default_argc = 0;
 const char** default_argv = NULL;
 
+interval_t duration_string_to_interval(const char* time_spec, const char* units) {
+  interval_t duration = 0LL;
+
+#if defined(PLATFORM_ARDUINO)
+  duration = atol(time_spec);
+#else
+  duration = atoll(time_spec);
+#endif
+
+  // A parse error returns 0LL, so check to see whether that is what is meant.
+  if (duration == 0LL && strncmp(time_spec, "0", 1) != 0) {
+    // Parse error.
+    return -1;
+  }
+  if (strncmp(units, "sec", 3) == 0) {
+    duration = SEC(duration);
+  } else if (strncmp(units, "msec", 4) == 0) {
+    duration = MSEC(duration);
+  } else if (strncmp(units, "usec", 4) == 0) {
+    duration = USEC(duration);
+  } else if (strncmp(units, "nsec", 4) == 0) {
+    duration = NSEC(duration);
+  } else if (strncmp(units, "min", 3) == 0) {
+    duration = MINUTE(duration);
+  } else if (strncmp(units, "hour", 4) == 0) {
+    duration = HOUR(duration);
+  } else if (strncmp(units, "day", 3) == 0) {
+    duration = DAY(duration);
+  } else if (strncmp(units, "week", 4) == 0) {
+    duration = WEEK(duration);
+  } else {
+    // Invalid units.
+    return -1;
+  }
+  return duration;
+}
+
 /**
  * Process the command-line arguments. If the command line arguments are not
  * understood, then print a usage message and return 0. Otherwise, return 1.
@@ -934,42 +980,30 @@ int process_args(int argc, const char* argv[]) {
       }
       const char* time_spec = argv[i++];
       const char* units = argv[i++];
-
-#if defined(PLATFORM_ARDUINO)
-      duration = atol(time_spec);
-#else
-      duration = atoll(time_spec);
-#endif
-
-      // A parse error returns 0LL, so check to see whether that is what is meant.
-      if (duration == 0LL && strncmp(time_spec, "0", 1) != 0) {
-        // Parse error.
-        lf_print_error("Invalid time value: %s", time_spec);
+      duration = duration_string_to_interval(time_spec, units);
+      if (duration < 0) {
+        lf_print_error("Invalid time units for --timeout.");
         usage(argc, argv);
         return 0;
       }
-      if (strncmp(units, "sec", 3) == 0) {
-        duration = SEC(duration);
-      } else if (strncmp(units, "msec", 4) == 0) {
-        duration = MSEC(duration);
-      } else if (strncmp(units, "usec", 4) == 0) {
-        duration = USEC(duration);
-      } else if (strncmp(units, "nsec", 4) == 0) {
-        duration = NSEC(duration);
-      } else if (strncmp(units, "min", 3) == 0) {
-        duration = MINUTE(duration);
-      } else if (strncmp(units, "hour", 4) == 0) {
-        duration = HOUR(duration);
-      } else if (strncmp(units, "day", 3) == 0) {
-        duration = DAY(duration);
-      } else if (strncmp(units, "week", 4) == 0) {
-        duration = WEEK(duration);
-      } else {
-        // Invalid units.
-        lf_print_error("Invalid time units: %s", units);
+    } else if (strcmp(arg, "-s") == 0 || strcmp(arg, "--start-time") == 0) {
+      if (argc < i + 2) {
+        lf_print_error("--start-time needs time and units.");
+        usage(argc, argv);
+        return 0;
+      }
+
+      const char* time_spec = argv[i++];
+      const char* units = argv[i++];
+      start_time = duration_string_to_interval(time_spec, units);
+      if (start_time < 0) {
+        lf_print_error("Invalid time units for --start-time.");
         usage(argc, argv);
         return 0;
+      } else {
+        start_time_specified = true;
       }
+
     } else if (strcmp(arg, "-k") == 0 || strcmp(arg, "--keepalive") == 0) {
       if (argc < i + 1) {
         lf_print_error("--keepalive needs a boolean.");
@@ -1227,3 +1261,15 @@ index_t lf_combine_deadline_and_level(interval_t deadline, int level) {
   else
     return (deadline << 16) | level;
 }
+
+void _lf_set_and_wait_for_start_time() {
+  if (!start_time_specified) {
+    start_time = lf_time_physical();
+  } else {
+    instant_t now = lf_time_physical();
+    if (!fast && now < start_time) {
+      lf_print("Sleeping " PRINTF_TIME " ns until specified start time", start_time - now);
+      lf_sleep(start_time - now);
+    }
+  }
+}

core/threaded/reactor_threaded.c

@@ -1017,7 +1017,9 @@ int lf_reactor_c_main(int argc, const char* argv[]) {
 
   // Initialize the clock through the platform API. No reading of physical time before this.
   _lf_initialize_clock();
-  start_time = lf_time_physical();
+  // Set the start time of the program (if it is not set from the command line). Possibly wait for
+  // it to arrive also.
+  _lf_set_and_wait_for_start_time();
 #ifndef FEDERATED
   lf_tracing_set_start_time(start_time);
 #endif

include/core/reactor_common.h

@@ -53,6 +53,7 @@ extern unsigned int _lf_number_of_workers;
 extern int default_argc;
 extern const char** default_argv;
 extern instant_t duration;
+extern bool start_time_specified;
 extern bool fast;
 extern bool keepalive_specified;
 
@@ -65,6 +66,11 @@ extern struct allocation_record_t* _lf_reactors_to_free;
 
 //////////////////////  Functions  //////////////////////
 
+/**
+ * @brief Set the start time of the program and possibly wait for it to arrive.
+ */
+void _lf_set_and_wait_for_start_time();
+
 /**
  * @brief Combine a deadline and a level into a single index for sorting in the reaction queue.
  *