Seems to be working

lerobot/common/policies/act/modeling_act.py

@@ -135,28 +135,22 @@ class ACTPolicy(
         return actions
 
     def inference_loop(self):
-        prev_timestamp = None
         while not self.stop_event.is_set():
-            last_observation, last_timestamp = self._obs_queue.get_latest()
-
-            if prev_timestamp is not None and prev_timestamp == last_timestamp:
-                # in case inference ran faster than recording/adding a new observation in the queue
-                # print("WAIT INFERENCE")
-                time.sleep(0.1)
-                continue
+            with self.condition:
+                self.condition.wait()
 
                 start_t = time.perf_counter()
 
+                last_observation, last_timestamp = self._obs_queue.get_latest()
                 pred_action_sequence = self.inference(last_observation)
+                self._action_seq_queue.add(pred_action_sequence, last_timestamp)
 
                 dt_s = time.perf_counter() - start_t
                 print(
                     f"Inference, {dt_s * 1000:5.2f} ({1/ dt_s:3.1f}hz) -- {last_timestamp}"
                 )  # , {next_action.mean().item()}")
 
-            self._action_seq_queue.add(pred_action_sequence, last_timestamp)
-
-            prev_timestamp = last_timestamp
+                self.new_action_seq_event.set()
 
     def select_action(self, batch: dict[str, Tensor]) -> Tensor:
         present_time = time.time()
@@ -164,27 +158,29 @@ class ACTPolicy(
 
         if self.thread is None:
             self.stop_event = threading.Event()
+            self.new_action_seq_event = threading.Event()
+
+            self.condition = threading.Condition()
             self.thread = Thread(target=self.inference_loop, args=())
             self.thread.daemon = True
             self.thread.start()
 
-        while len(self._action_seq_queue) == 0:
-            # print("WAIT")
-            time.sleep(0.1)  # no action available at this present time, we wait a bit
+            # Ask thread to run first inference
+            with self.condition:
+                self.condition.notify()
 
+            # Block main process until the thread ran it's first inference
+            self.new_action_seq_event.wait()
+            self._action_sequence, self._action_seq_timestamp = self._action_seq_queue.get_latest()
+
+        if self._action_seq_index == 97:
+            with self.condition:
+                self.condition.notify()
+
+        if self._action_seq_index >= len(self._action_sequence):
+            self.new_action_seq_event.wait()
             latest_action_sequence, latest_seq_timestamp = self._action_seq_queue.get_latest()
 
-        if self._action_seq_index == len(self.delta_timestamps["action"]):
-            while self._action_seq_timestamp == latest_seq_timestamp:
-                latest_action_sequence, latest_seq_timestamp = self._action_seq_queue.get_latest()
-                # print("WAIT")
-                time.sleep(0.1)
-
-        if self._action_seq_timestamp is None:
-            self._action_sequence = latest_action_sequence
-            self._action_seq_timestamp = latest_seq_timestamp
-
-        elif self._action_seq_index == 100 and self._action_seq_timestamp < latest_seq_timestamp:
             # update sequence index
             seq_timestamps = self._action_seq_timestamp + np.array(self.delta_timestamps["action"])
             if self._action_seq_index == len(self.delta_timestamps["action"]):

lerobot/common/robot_devices/utils.py

@@ -1,19 +1,17 @@
+import platform
 import time
 
 
 def busy_wait(seconds):
-    # if platform.system() == "Darwin":
-    #     # On Mac, `time.sleep` is not accurate and we need to use this while loop trick,
-    #     # but it consumes CPU cycles.
-    #     # TODO(rcadene): find an alternative: from python 11, time.sleep is precise
-    #     end_time = time.perf_counter() + seconds
-    #     while time.perf_counter() < end_time:
-    #         pass
-    # else:
-    #     # On Linux time.sleep is accurate
-    #     if seconds > 0:
-    #         time.sleep(seconds)
-
+    if platform.system() == "Darwin":
+        # On Mac, `time.sleep` is not accurate and we need to use this while loop trick,
+        # but it consumes CPU cycles.
+        # TODO(rcadene): find an alternative: from python 11, time.sleep is precise
+        end_time = time.perf_counter() + seconds
+        while time.perf_counter() < end_time:
+            pass
+    else:
+        # On Linux time.sleep is accurate
         if seconds > 0:
             time.sleep(seconds)