bartorch.nlop.NonlinearOperator

class bartorch.nlop.NonlinearOperator

A map between shapes, with a derivative and its adjoint.

derivative() and adjoint() are taken at the point of the last forward() call, which is how BART’s solvers use them. The backward pass of F(x) is adjoint at that point, so evaluating the operator elsewhere between a forward and a backward pass gives a wrong gradient.

An operator may take more than one input and return more than one output; ishapes and oshapes are the shape of each, and ishape and oshape are the whole of it when there is one of each. The algebra in bartorch.nlop is what builds the many-argument ones: combine(), chain(), link(), dup().

A subclass is defined either by _create(), which builds one of BART’s operators, or in Python by forward(), derivative() and adjoint().

ishapes, oshapes

The shape of each input and of each output, C order.

Type:

tuple of tuple of int

ishape, oshape

Domain and codomain, for an operator with one input and one output.

Type:

tuple of int

__init__()

Methods

__init__()
adjoint(dy)	DF(x)^H dy at the last evaluated point, for one input and one output.
chain(other, *[, output, input])	Output output of self into input input of other.
combine(other)	self and other side by side, sharing nothing.
del_out([output])	Drop an output, and everything computed only for it.
derivative(dx)	DF(x) dx at the last evaluated point, for one input and one output.
dup([a, b])	Make two inputs of the same shape one input, kept at a.
flatten([inputs_only])	Every input as one flat vector, and every output as another.
forward(*xs)	F(x), which also fixes where every derivative is taken.
jacobian([output, input])	DF/dx_input of one output, as a LinearOperator.
linearize(*xs)	The derivative at x, as a LinearOperator.
link([output, input])	Tie an output back into an input; both arguments go away.
permute_inputs(perm)	Reorder the inputs: the new input i is the old perm[i].
permute_outputs(perm)	Reorder the outputs: the new output o is the old perm[o].
pin(input, value)	Fix one input to value; the input goes away.
reshape_input(input, shape)	This operator with one input's shape written differently.
reshape_output(output, shape)	This operator with one output's shape written differently.
shift_input(new, old)	Move one input to another position, the rest closing up behind it.
shift_output(new, old)	Move one output to another position, the rest closing up behind it.
stack_inputs(a, b, axis)	Make two inputs one, concatenated along a C-order axis.
stack_outputs(a, b, axis)	Make two outputs one, concatenated along a C-order axis.

Attributes

device
ishape	The domain, for an operator with one input.
ishapes	The shape of each argument, outputs and inputs kept apart.
oshape	The codomain, for an operator with one output.
oshapes