Other Functions and Classes

class tf.DeviceSpec

Represents a (possibly partial) specification for a TensorFlow device.

DeviceSpecs are used throughout TensorFlow to describe where state is stored and computations occur. Using DeviceSpec allows you to parse device spec strings to verify their validity, merge them or compose them programmatically.


# Place the operations on device "GPU:0" in the "ps" job.
device_spec = DeviceSpec(job="ps", device_type="GPU", device_index=0)
with tf.device(device_spec):
  # Both my_var and squared_var will be placed on /job:ps/device:GPU:0.
  my_var = tf.Variable(..., name="my_variable")
  squared_var = tf.square(my_var)

If a DeviceSpec is partially specified, it will be merged with other DeviceSpecs according to the scope in which it is defined. DeviceSpec components defined in inner scopes take precedence over those defined in outer scopes.

with tf.device(DeviceSpec(job="train", )):
  with tf.device(DeviceSpec(job="ps", device_type="GPU", device_index=0):
    # Nodes created here will be assigned to /job:ps/device:GPU:0.
  with tf.device(DeviceSpec(device_type="GPU", device_index=1):
    # Nodes created here will be assigned to /job:train/device:GPU:1.

A DeviceSpec consists of 5 components -- each of which is optionally specified:

  • Job: The job name.
  • Replica: The replica index.
  • Task: The task index.
  • Device type: The device type string (e.g. "CPU" or "GPU").
  • Device index: The device index.

tf.DeviceSpec.__init__(job=None, replica=None, task=None, device_type=None, device_index=None) {:#DeviceSpec.init}

Create a new DeviceSpec object.

  • job: string. Optional job name.
  • replica: int. Optional replica index.
  • task: int. Optional task index.
  • device_type: Optional device type string (e.g. "CPU" or "GPU")
  • device_index: int. Optional device index. If left unspecified, device represents 'any' device_index.


Construct a DeviceSpec from a string.

  • spec: a string of the form /job:/replica:/task:/device:CPU: or /job:/replica:/task:/device:GPU: as cpu and gpu are mutually exclusive. All entries are optional.

A DeviceSpec.



Merge the properties of "dev" into this DeviceSpec.

  • dev: a DeviceSpec.


Parse a DeviceSpec name into its components.

  • spec: a string of the form /job:/replica:/task:/device:CPU: or /job:/replica:/task:/device:GPU: as cpu and gpu are mutually exclusive. All entries are optional.

The DeviceSpec.

  • ValueError: if the spec was not valid.




Return a string representation of this DeviceSpec.


a string of the form /job:/replica:/task:/device::.

class tf.bytes

str(object='') -> string

Return a nice string representation of the object. If the argument is a string, the return value is the same object.