tf.distribute.get_replica_context

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Returns the current tf.distribute.ReplicaContext or None.

tf.distribute.get_replica_context()

Returns None if in a cross-replica context.

Note that execution:

  1. starts in the default (single-replica) replica context (this function will return the default ReplicaContext object);
  2. switches to cross-replica context (in which case this will return None) when entering a with tf.distribute.Strategy.scope(): block;
  3. switches to a (non-default) replica context inside strategy.run(fn, ...);
  4. if fn calls get_replica_context().merge_call(merge_fn, ...), then inside merge_fn you are back in the cross-replica context (and again this function will return None).

Most tf.distribute.Strategy methods may only be executed in a cross-replica context, in a replica context you should use the API of the tf.distribute.ReplicaContext object returned by this method instead.

assert tf.distribute.get_replica_context() is not None  # default
with strategy.scope():
  assert tf.distribute.get_replica_context() is None

  def f():
    replica_context = tf.distribute.get_replica_context()  # for strategy
    assert replica_context is not None
    tf.print("Replica id: ", replica_context.replica_id_in_sync_group,
             " of ", replica_context.num_replicas_in_sync)

  strategy.run(f)

The current tf.distribute.ReplicaContext object when in a replica context scope, else None.

Within a particular block, exactly one of these two things will be true:

  • get_replica_context() returns non-None, or
  • tf.distribute.is_cross_replica_context() returns True.