Context-manager that disables gradient calculation.
Disabling gradient calculation is useful for inference, when you are sure that you will not call Tensor.backward()
. It will reduce memory consumption for computations that would otherwise have requires_grad=True.
In this mode, the result of every computation will have requires_grad=False, even when the inputs have requires_grad=True. There is an exception! All factory functions, or functions that create a new Tensor and take a requires_grad kwarg, will NOT be affected by this mode.
This context manager is thread local; it will not affect computation in other threads.
Also functions as a decorator.
Note
This API does not apply to forward-mode AD. If you want to disable forward AD for a computation, you can unpack your dual tensors.
>>> x = torch.tensor([1.], requires_grad=True) >>> with torch.no_grad(): ... y = x * 2 >>> y.requires_grad False >>> @torch.no_grad() ... def doubler(x): ... return x * 2 >>> z = doubler(x) >>> z.requires_grad False >>> @torch.no_grad() ... def tripler(x): ... return x * 3 >>> z = tripler(x) >>> z.requires_grad False >>> # factory function exception >>> with torch.no_grad(): ... a = torch.nn.Parameter(torch.rand(10)) >>> a.requires_grad True
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