nlop.TorchOperator

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nlop.TorchOperator#

class bartorch.nlop.TorchOperator#

Bases: NonlinearOperator

A nonlinear operator from a differentiable torch function.

The derivative is torch’s forward-mode Jacobian-vector product, and its adjoint the reverse-mode vector-Jacobian product, both at the last evaluated point.

Parameters:

  • fn (callable) – A differentiable function on tensors. With several input shapes it takes that many arguments, and it may return several tensors.

  • ishape (tuple of int, or a sequence of them) – Domain and codomain, C order.

  • oshape (tuple of int, or a sequence of them) – Domain and codomain, C order.

Examples

>>> F = TorchOperator(lambda p: p[0] * torch.exp(-t / p[1]), (2,), t.shape)
>>> nlop.IRGNM()(measured, F, x0=torch.tensor([1.0, 20.0]))

Notes

A real argument is carried in the real part of a complex one: BART’s operators are complex throughout, so a weight arrives as w + 0j and its gradient comes back complex. Take the real part of it.

Also has the methods and properties of NonlinearOperator.

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