tf.DeviceSpec

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

tf.DeviceSpec(
    job=None, replica=None, task=None, device_type=None, device_index=None
)

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.

Example:

# 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.

Args:

• 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.

Attributes:

• device_index
• device_type
• job
• replica
• task

Methods

__eq__

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__eq__(
    other
)

Checks if the other DeviceSpec is same as the current instance, eg have

same value for all the internal fields.

Args:

• other: Another DeviceSpec

Returns:

Return True if other is also a DeviceSpec instance and has same value as the current instance. Return False otherwise.

from_string

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@classmethod
from_string(
    spec
)

Construct a DeviceSpec from a string.

Args:

• 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.

Returns:

A DeviceSpec.

make_merged_spec

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make_merged_spec(
    dev
)

Returns a new DeviceSpec which incorporates dev.

When combining specs, dev will take precidence over the current spec. So for instance: first_spec = tf.DeviceSpec(job=0, device_type="CPU") second_spec = tf.DeviceSpec(device_type="GPU") combined_spec = first_spec.make_merged_spec(second_spec)

is equivalent to: combined_spec = tf.DeviceSpec(job=0, device_type="GPU")

Args:

• dev: a DeviceSpec

Returns:

A new DeviceSpec which combines self and dev

parse_from_string

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parse_from_string(
    spec
)

Parse a DeviceSpec name into its components.

2.x behavior change: In TensorFlow 1.x, this function mutates its own state and returns itself. In 2.x, DeviceSpecs are immutable, and this function will return a DeviceSpec which contains the spec.

Recommended: # my_spec and my_updated_spec are unrelated. my_spec = tf.DeviceSpec.from_string("/CPU:0") my_updated_spec = tf.DeviceSpec.from_string("/GPU:0") with tf.device(my_updated_spec): ...

Will work in 1.x and 2.x (though deprecated in 2.x): my_spec = tf.DeviceSpec.from_string("/CPU:0") my_updated_spec = my_spec.parse_from_string("/GPU:0") with tf.device(my_updated_spec): ...

Will NOT work in 2.x: my_spec = tf.DeviceSpec.from_string("/CPU:0") my_spec.parse_from_string("/GPU:0") # <== Will not update my_spec with tf.device(my_spec): ...

In general, DeviceSpec.from_string should completely replace DeviceSpec.parse_from_string, and DeviceSpec.replace should completely replace setting attributes directly.

Args:

• spec: an optional 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.

Returns:

The DeviceSpec.

Raises:

• ValueError: if the spec was not valid.

replace

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replace(
    **kwargs
)

Convenience method for making a new DeviceSpec by overriding fields.

For instance:

my_spec = DeviceSpec=(job="my_job", device="CPU")
my_updated_spec = my_spec.replace(device="GPU")
my_other_spec = my_spec.replace(device=None)

Args:

• **kwargs: This method takes the same args as the DeviceSpec constructor

Returns:

A DeviceSpec with the fields specified in kwargs overridden.

to_string

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to_string()

Return a string representation of this DeviceSpec.

Returns:

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