# tf.train.batch_join

tf.train.batch_join(
tensors_list,
batch_size,
capacity=32,
enqueue_many=False,
shapes=None,
allow_smaller_final_batch=False,
shared_name=None,
name=None
)


See the guide: Inputs and Readers > Input pipeline

Runs a list of tensors to fill a queue to create batches of examples.

The tensors_list argument is a list of tuples of tensors, or a list of dictionaries of tensors. Each element in the list is treated similarly to the tensors argument of tf.train.batch().

WARNING: This function is nondeterministic, since it starts a separate thread for each tensor.

Enqueues a different list of tensors in different threads. Implemented using a queue -- a QueueRunner for the queue is added to the current Graph's QUEUE_RUNNER collection.

len(tensors_list) threads will be started, with thread i enqueuing the tensors from tensors_list[i]. tensors_list[i1][j] must match tensors_list[i2][j] in type and shape, except in the first dimension if enqueue_many is true.

If enqueue_many is False, each tensors_list[i] is assumed to represent a single example. An input tensor x will be output as a tensor with shape [batch_size] + x.shape.

If enqueue_many is True, tensors_list[i] is assumed to represent a batch of examples, where the first dimension is indexed by example, and all members of tensors_list[i] should have the same size in the first dimension. The slices of any input tensor x are treated as examples, and the output tensors will have shape [batch_size] + x.shape[1:].

The capacity argument controls the how long the prefetching is allowed to grow the queues.

The returned operation is a dequeue operation and will throw tf.errors.OutOfRangeError if the input queue is exhausted. If this operation is feeding another input queue, its queue runner will catch this exception, however, if this operation is used in your main thread you are responsible for catching this yourself.

N.B.: If dynamic_pad is False, you must ensure that either (i) the shapes argument is passed, or (ii) all of the tensors in tensors_list must have fully-defined shapes. ValueError will be raised if neither of these conditions holds.

If dynamic_pad is True, it is sufficient that the rank of the tensors is known, but individual dimensions may have value None. In this case, for each enqueue the dimensions with value None may have a variable length; upon dequeue, the output tensors will be padded on the right to the maximum shape of the tensors in the current minibatch. For numbers, this padding takes value 0. For strings, this padding is the empty string. See PaddingFIFOQueue for more info.

If allow_smaller_final_batch is True, a smaller batch value than batch_size is returned when the queue is closed and there are not enough elements to fill the batch, otherwise the pending elements are discarded. In addition, all output tensors' static shapes, as accessed via the shape property will have a first Dimension value of None, and operations that depend on fixed batch_size would fail.

#### Args:

• tensors_list: A list of tuples or dictionaries of tensors to enqueue.
• batch_size: An integer. The new batch size pulled from the queue.
• capacity: An integer. The maximum number of elements in the queue.
• enqueue_many: Whether each tensor in tensor_list_list is a single example.
• shapes: (Optional) The shapes for each example. Defaults to the inferred shapes for tensor_list_list[i].
• dynamic_pad: Boolean. Allow variable dimensions in input shapes. The given dimensions are padded upon dequeue so that tensors within a batch have the same shapes.
• allow_smaller_final_batch: (Optional) Boolean. If True, allow the final batch to be smaller if there are insufficient items left in the queue.
• shared_name: (Optional) If set, this queue will be shared under the given name across multiple sessions.
• name: (Optional) A name for the operations.

#### Returns:

A list or dictionary of tensors with the same number and types as tensors_list[i].

#### Raises:

• ValueError: If the shapes are not specified, and cannot be inferred from the elements of tensor_list_list.

#### Eager Compatibility

Input pipelines based on Queues are not supported when eager execution is enabled. Please use the tf.data API to ingest data under eager execution.