TensorFlow如何使用类表示设备
2018-09-30 17:43 更新
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＃ =============================================== =============================
“”“表示设备的类”.“”
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function
import copy
class DeviceSpec(object):
"""Represents a (possibly partial) specification for a TensorFlow device.
`DeviceSpec`s 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:
```python
# 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
`DeviceSpec`s according to the scope in which it is defined. `DeviceSpec`
components defined in inner scopes take precedence over those defined in
outer scopes.
```python
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.
"""
def __init__(self, job=None, replica=None, task=None, device_type=None,
device_index=None):
"""Create a new `DeviceSpec` object.
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.
"""
self.job = job
self.replica = replica
self.task = task
if device_type == "cpu" or device_type == "gpu":
# For backwards compatibility only, we support lowercase variants of
# cpu and gpu but turn them into uppercase here.
self.device_type = device_type.upper()
else:
self.device_type = device_type
self.device_index = device_index
def _clear(self):
self._job = None
self._replica = None
self._task = None
self.device_type = None
self.device_index = None
@property
def job(self):
return self._job
@job.setter
def job(self, job):
if job is not None:
self._job = str(job)
else:
self._job = None
@property
def replica(self):
return self._replica
@replica.setter
def replica(self, replica):
if replica is not None:
self._replica = int(replica)
else:
self._replica = None
@property
def task(self):
return self._task
@task.setter
def task(self, task):
if task is not None:
self._task = int(task)
else:
self._task = None
def parse_from_string(self, spec):
"""Parse a `DeviceSpec` name into its components.
Args:
spec: a string of the form
/job:<name>/replica:<id>/task:<id>/device:CPU:<id>
or
/job:<name>/replica:<id>/task:<id>/device:GPU:<id>
as cpu and gpu are mutually exclusive.
All entries are optional.
Returns:
The `DeviceSpec`.
Raises:
ValueError: if the spec was not valid.
"""
self._clear()
splits = [x.split(":") for x in spec.split("/")]
for y in splits:
ly = len(y)
if y:
# NOTE(touts): we use the property getters here.
if ly == 2 and y[0] == "job":
self.job = y[1]
elif ly == 2 and y[0] == "replica":
self.replica = y[1]
elif ly == 2 and y[0] == "task":
self.task = y[1]
elif ((ly == 1 or ly == 2) and
((y[0].upper() == "GPU") or (y[0].upper() == "CPU"))):
if self.device_type is not None:
raise ValueError("Cannot specify multiple device types: %s" % spec)
self.device_type = y[0].upper()
if ly == 2 and y[1] != "*":
self.device_index = int(y[1])
elif ly == 3 and y[0] == "device":
if self.device_type is not None:
raise ValueError("Cannot specify multiple device types: %s" % spec)
self.device_type = y[1]
if y[2] != "*":
self.device_index = int(y[2])
elif ly and y[0] != "": # pylint: disable=g-explicit-bool-comparison
raise ValueError("Unknown attribute: '%s' in '%s'" % (y[0], spec))
return self
def merge_from(self, dev):
"""Merge the properties of "dev" into this `DeviceSpec`.
Args:
dev: a `DeviceSpec`.
"""
if dev.job is not None:
self.job = dev.job
if dev.replica is not None:
self.replica = dev.replica
if dev.task is not None:
self.task = dev.task
if dev.device_type is not None:
self.device_type = dev.device_type
if dev.device_index is not None:
self.device_index = dev.device_index
def to_string(self):
"""Return a string representation of this `DeviceSpec`.
Returns:
a string of the form
/job:<name>/replica:<id>/task:<id>/device:<device_type>:<id>.
"""
dev = ""
if self.job is not None:
dev += "/job:" + self.job
if self.replica is not None:
dev += "/replica:" + str(self.replica)
if self.task is not None:
dev += "/task:" + str(self.task)
if self.device_type is not None:
device_index_string = "*"
if self.device_index is not None:
device_index_string = str(self.device_index)
dev += "/device:%s:%s" % (self.device_type, device_index_string)
return dev
@staticmethod
def from_string(spec):
"""Construct a `DeviceSpec` from a string.
Args:
spec: a string of the form
/job:<name>/replica:<id>/task:<id>/device:CPU:<id>
or
/job:<name>/replica:<id>/task:<id>/device:GPU:<id>
as cpu and gpu are mutually exclusive.
All entries are optional.
Returns:
A DeviceSpec.
"""
return DeviceSpec().parse_from_string(spec)
def check_valid(spec):
"""Check that a device spec is valid.
Args:
spec: a string.
Raises:
An exception if the spec is invalid.
"""
# Construct a DeviceSpec. It will assert a failure if spec is invalid.
DeviceSpec.from_string(spec)
def canonical_name(device):
"""Returns a canonical name for the given `DeviceSpec` or device name."""
if device is None:
return ""
if isinstance(device, DeviceSpec):
return device.to_string()
else:
device = DeviceSpec.from_string(device)
return device.to_string()
def merge_device(spec):
"""Returns a device function that merges devices specifications.
This can be used to merge partial specifications of devices. The
innermost setting for a device field takes precedence. For example:
with tf.device(merge_device("/device:GPU:0"))
# Nodes created here have device "/device:GPU:0"
with tf.device(merge_device("/job:worker")):
# Nodes created here have device "/job:worker/device:GPU:0"
with tf.device(merge_device("/device:CPU:0")):
# Nodes created here have device "/job:worker/device:CPU:0"
with tf.device(merge_device("/job:ps")):
# Nodes created here have device "/job:ps/device:CPU:0"
Args:
spec: A `DeviceSpec` or a device spec string (partially) describing the
device that should be used for all nodes created in the scope of
the returned device function's with block.
Returns:
A device function with the above-described behavior.
Raises:
ValueError: if the spec was not valid.
"""
if not isinstance(spec, DeviceSpec):
spec = DeviceSpec.from_string(spec or "")
def _device_function(node_def):
current_device = DeviceSpec.from_string(node_def.device or "")
copy_spec = copy.copy(spec)
copy_spec.merge_from(current_device) # current_device takes precedence.
return copy_spec
return _device_function