nifty8.operators.inversion_enabler module

class InversionEnabler(op, iteration_controller, approximation=None)

Bases: EndomorphicOperator

Class which augments the capability of another operator object via numerical inversion.

Parameters:

• op (EndomorphicOperator) – The operator to be enhanced. The InversionEnabler object will support the same operation modes as op, and additionally the inverse set. The newly-added modes will be computed by iterative inversion.

• iteration_controller (IterationController) – The iteration controller to use for the iterative numerical inversion done by a ConjugateGradient object.

• approximation (LinearOperator, optional) – if not None, this operator should be an approximation to op, which supports the operation modes that op doesn’t have. It is used as a preconditioner during the iterative inversion, to accelerate convergence.

__init__(op, iteration_controller, approximation=None)

apply(x, mode)

Applies the Operator to a given x, in a specified mode.

Parameters:

• x (nifty8.field.Field) – The input Field, defined on the Operator’s domain or target, depending on mode.

• mode (int) –

  • TIMES: normal application

  • ADJOINT_TIMES: adjoint application

  • INVERSE_TIMES: inverse application

  • ADJOINT_INVERSE_TIMES or INVERSE_ADJOINT_TIMES: adjoint inverse application

Returns:

The processed Field defined on the Operator’s target or domain, depending on mode.

Return type:

nifty8.field.Field

draw_sample(from_inverse=False)

Generates a sample from a Gaussian distribution with zero mean and covariance given by the operator.

May or may not be implemented. Only optional.

Parameters:

from_inverse (bool (default : False)) – if True, the sample is drawn from the inverse of the operator

Returns:

A sample from the Gaussian of given covariance.

Return type:

nifty8.field.Field or nifty8.multi_field.MultiField