[r2.0 CherryPick]: @tf.function: Show a warning message when tracing happens too frequently

tensorflow/python/eager/def_function.py

@@ -38,6 +38,41 @@
 from tensorflow.python.util import tf_decorator
 from tensorflow.python.util.tf_export import tf_export
 
+FREQUENT_TRACING_WARNING_MAX_CALL_HISTORY = 10
+FREQUENT_TRACING_WARNING_THRESHOLD = 5
+
+
+class _CallCounter(object):
+  """Class keeping track of how many recent calls triggered tracing."""
+
+  def __init__(self, max_call_history):
+    self._max_call_history = max_call_history
+    self._calls_per_tracings = []
+    self.call_count = 0
+
+  def called_with_tracing(self):
+    self.call_count += 1
+    self._calls_per_tracings.append(1)
+
+    while self._calls_per_tracings:
+      if self.call_count - self._calls_per_tracings[0] > self._max_call_history:
+        self.call_count -= self._calls_per_tracings.pop(0)
+      else:
+        break
+
+  def called_without_tracing(self):
+    # TODO(kkimlabs): This is an unnecessary defensive check. Since this is last
+    # minute CL before 2.0 release, I've decided to be very defensive here to
+    # avoid a potential crash. Remove once we release 2.0.
+    if not self._calls_per_tracings:
+      return
+
+    self._calls_per_tracings[-1] += 1
+    self.call_count += 1
+
+  def get_tracing_count(self):
+    return len(self._calls_per_tracings)
+
 
 class UnliftedInitializerVariable(resource_variable_ops.UninitializedVariable):
   """Variable which does not lift its initializer out of function context.
@@ -297,6 +332,7 @@ def __init__(self,
     self._stateless_fn = None  # GUARDED_BY(self._lock)
     self._descriptor_cache = weakref.WeakKeyDictionary()
     self._name = name
+    self._call_counter = _CallCounter(FREQUENT_TRACING_WARNING_MAX_CALL_HISTORY)
 
   def _defun_with_scope(self, scope):
     """Creates a defun wrapped inside a variable creator scope."""
@@ -406,11 +442,41 @@ def _decorate(self, decorator):
     self._function_spec = function_lib.FunctionSpec.from_function_and_signature(
         self._python_function, self.input_signature)
 
+  def _get_tracing_count(self):
+    result = self._stateless_fn.tracing_count if self._stateless_fn else 0
+    result += self._stateful_fn.tracing_count if self._stateful_fn else 0
+    return result
+
   def __call__(self, *args, **kwds):
-    """Calls the graph function."""
+    """Calls the graph function and warn too frequent tracings."""
     context.ensure_initialized()
     if RUN_FUNCTIONS_EAGERLY:
       return self._python_function(*args, **kwds)
+
+    tracing_count = self._get_tracing_count()
+    result = self._call(*args, **kwds)
+    if tracing_count == self._get_tracing_count():
+      self._call_counter.called_without_tracing()
+      return result
+
+    self._call_counter.called_with_tracing()
+    recent_tracing_count = self._call_counter.get_tracing_count()
+    if recent_tracing_count >= FREQUENT_TRACING_WARNING_THRESHOLD:
+      logging.warning(
+          "{} out of the last {} calls to {} triggered tf.function retracing. "
+          "Tracing is expensive and the excessive number of tracings is likely "
+          "due to passing python objects instead of tensors. Also, tf.function "
+          "has experimental_relax_shapes=True option that relaxes argument "
+          "shapes that can avoid unnecessary retracing. Please refer to "
+          "https://www.tensorflow.org/beta/tutorials/eager/tf_function#python_or_tensor_args"
+          " and https://www.tensorflow.org/api_docs/python/tf/function for more "
+          "details.".format(recent_tracing_count, self._call_counter.call_count,
+                            self._python_function))
+
+    return result
+
+  def _call(self, *args, **kwds):
+    """Calls the graph function."""
     self._lock.acquire()
     if self._created_variables:
       # Release the lock early so that multiple threads can perform the call

tensorflow/python/eager/function.py

@@ -1809,6 +1809,7 @@ def __init__(self,
     self._function_cache = FunctionCache()
     self._function_attributes = attributes or {}
     self._capture_by_value = capture_by_value
+    self.tracing_count = 0
 
     self._lock = threading.Lock()
     # _descriptor_cache is a of instance of a class to an instance-specific
@@ -2011,6 +2012,8 @@ def _cache_key(self, args, kwargs, include_tensor_ranks_only=False):
 
   def _create_graph_function(self, args, kwargs, override_flat_arg_shapes=None):
     """Create a `ConcreteFunction` from `args` and `kwargs`."""
+    self.tracing_count += 1
+
     if self.input_signature is None:
       arglen = len(args)
     else: