enable_grad

class tensorplay.autograd.grad_mode.enable_grad(orig_func=None)[source]

Context-manager that enables gradient calculation.

Enables gradient calculation, if it has been disabled via no_grad or set_grad_enabled.

This context manager is thread local; it will not affect computation in other threads.

Also functions as a decorator.

Note

enable_grad is one of several mechanisms that can enable or disable gradients locally see Locally disabling gradient computation for more information on how they compare.

Note

This API does not apply to forward-mode AD.

Example::

>>> # xdoctest: +SKIP
>>> x = tensorplay.tensor([1.], requires_grad=True)
>>> with tensorplay.no_grad():
...     with tensorplay.enable_grad():
...         y = x * 2
>>> y.requires_grad
True
>>> y.backward()
>>> x.grad
tensor([2.])
>>> @tensorplay.enable_grad()
... def doubler(x):
...     return x * 2
>>> with tensorplay.no_grad():
...     z = doubler(x)
>>> z.requires_grad
True
>>> @tensorplay.enable_grad()
... def tripler(x):
...     return x * 3
>>> with tensorplay.no_grad():
...     z = tripler(x)
>>> z.requires_grad
True