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tf.TensorArray

Class wrapping dynamic-sized, per-time-step, write-once Tensor arrays.

Used in the notebooks

Used in the guide Used in the tutorials

This class is meant to be used with dynamic iteration primitives such as while_loop and map_fn. It supports gradient back-propagation via special "flow" control flow dependencies.

Example 1: Plain reading and writing.

ta = tf.TensorArray(tf.float32, size=0, dynamic_size=True, clear_after_read=False)
ta = ta.write(0, 10)
ta = ta.write(1, 20)
ta = ta.write(2, 30)

ta.read(0)
<tf.Tensor: shape=(), dtype=float32, numpy=10.0>
ta.read(1)
<tf.Tensor: shape=(), dtype=float32, numpy=20.0>
ta.read(2)
<tf.Tensor: shape=(), dtype=float32, numpy=30.0>
ta.stack()
<tf.Tensor: shape=(3,), dtype=float32, numpy=array([10., 20., 30.],
dtype=float32)>

Example 2: Fibonacci sequence algorithm that writes in a loop then returns.

@tf.function
def fibonacci(n):
  ta = tf.TensorArray(tf.float32, size=0, dynamic_size=True)
  ta = ta.unstack([0., 1.])

  for i in range(2, n):
    ta = ta.write(i, ta.read(i - 1) + ta.read(i - 2))

  return ta.stack()

fibonacci(7)
<tf.Tensor: shape=(7,), dtype=float32,
numpy=array([0., 1., 1., 2., 3., 5., 8.], dtype=float32)>

Example 3: A simple loop interacting with a tf.Variable.

v = tf.Variable(1)
@tf.function
def f(x):
  ta = tf.TensorArray(tf.int32, size=0, dynamic_size=True)
  for i in tf.range(x):
    v.assign_add(i)
    ta = ta.write(i, v)
  return ta.stack()
f(5)
<tf.Tensor: shape=(5,), dtype=int32, numpy=array([ 1,  2,  4,  7, 11],
dtype=int32)>

dtype (required) data type of the TensorArray.
size (optional) int32 scalar Tensor: the size of the TensorArray. Required if handle is not provided.
dynamic_size (optional) Python bool: If true, writes to the TensorArray can grow the TensorArray past its initial size. Default: False.
clear_after_read Boolean (optional, default: True). If True, clear TensorArray values after reading them. This disables read-many semantics, but allows early release of memory.
tensor_array_name (optional) Python string: the name of the TensorArray. This is used when creating the TensorArray handle. If this value is set, handle should be None.
handle (optional) A Tensor handle to an existing TensorArray. If this is set, tensor_array_name should be None. Only supported in graph mode.
flow (optional) A float Tensor scalar coming from an existing TensorArray.flow. Only supported in graph mode.
infer_shape (optional, default: True) If True, shape inference is enabled. In this case, all elements must have the same shape.
element_shape (optional, default: None) A TensorShape object specifying the shape constraints of each of the elements of the TensorArray. Need not be fully defined.
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