qiskit.chemistry.algorithms.pes_samplers.PCAExtrapolator

class PCAExtrapolator(extrapolator=None, kernel=None, window=2)

A wrapper extrapolator which reduces the points’ dimensionality with PCA, performs extrapolation in the transformed pca space, and inverse transforms the results before returning. A user specifies the kernel within how the PCA transformation should be done.

Constructor.

Parameters

• extrapolator (Union[PolynomialExtrapolator, DifferentialExtrapolator, None]) – ‘internal’ extrapolator that performs extrapolation on variational parameters based on data window.

• kernel (Optional[str]) – Kernel (from sklearn) that specifies how dimensionality reduction should be done for PCA. Default value is None, and switches the extrapolation to standard PCA.

• window (int) – Number of previous points to use for extrapolation.

Raises

AquaError – if kernel is not defined in sklearn module.

__init__(extrapolator=None, kernel=None, window=2)

Constructor.

Parameters

• extrapolator (Union[PolynomialExtrapolator, DifferentialExtrapolator, None]) – ‘internal’ extrapolator that performs extrapolation on variational parameters based on data window.

• kernel (Optional[str]) – Kernel (from sklearn) that specifies how dimensionality reduction should be done for PCA. Default value is None, and switches the extrapolation to standard PCA.

• window (int) – Number of previous points to use for extrapolation.

Raises

AquaError – if kernel is not defined in sklearn module.

Methods

__init__([extrapolator, kernel, window])	Constructor.
extrapolate(points, param_dict)	Extrapolate at specified point of interest given a set of variational parameters.
factory(mode, **kwargs)	Factory method for constructing extrapolators.

extrapolate(points, param_dict)

Extrapolate at specified point of interest given a set of variational parameters. This method transforms the parameters in PCA space before performing the internal extrapolation. The parameters are transformed back to regular space after extrapolation.

Parameters

• points (List[float]) – List of point(s) to be used for extrapolation. Can represent some degree of freedom, ex, interatomic distance.

• param_dict (Optional[Dict[float, List[float]]]) – Dictionary of variational parameters. Each key is the point

• the value is a list of the variational parameters. (and) –

Return type

Dict[float, List[float]]

Returns

Dictionary of variational parameters for extrapolated point(s).

static factory(mode, **kwargs)

Factory method for constructing extrapolators.

Parameters

• mode (str) – Extrapolator to instantiate. Can be one of: - ‘window’ - ‘poly’ - ‘diff_model’ - ‘pca’ - ‘l1’

• kwargs – arguments to be passed to the constructor of an extrapolator

Return type

Extrapolator

Returns

A newly created extrapolator instance.

Raises

AquaError – if specified mode is unknown.