dwave.embedding.chain_breaks.weighted_random

weighted_random(samples, chains)

Unembed samples using weighed random choice for broken chains.

Parameters:

• samples (samples_like) – A collection of samples. samples_like is an extension of NumPy’s array_like. See dimod.as_samples().

• chains (list[array_like]) – List of chains, where each chain is an array_like collection of the variables in the same order as their represention in the given samples.

Returns:

A 2-tuple containing:

numpy.ndarray: Unembedded samples as an nS-by-nC array of dtype ‘int8’, where nC is the number of chains and nS the number of samples. Broken chains are resolved by setting the sample value to a random value weighted by frequency of the value in the chain.

numpy.ndarray: Indicies of the samples. Equivalent to np.arange(nS) because all samples are kept and no samples are added.

Return type:

tuple

Examples

This example unembeds samples from a target graph that chains nodes 0 and 1 to represent one source node and nodes 2, 3, and 4 to represent another. The sample has broken chains for both source nodes.

>>> import dimod
>>> import numpy as np
...
>>> chains = [(0, 1), (2, 3, 4)]
>>> samples = np.array([[1, 0, 1, 0, 1]], dtype=np.int8)
>>> unembedded, idx = dwave.embedding.weighted_random(samples, chains)  
>>> unembedded  
array([[1, 1]], dtype=int8)
>>> idx  
array([0, 1])