hybrid.utils.select_localsearch_adversaries

select_localsearch_adversaries(bqm, sample, max_n=None, min_gain=None)[source]

Find variable flips that contribute high energy changes to a BQM.

Parameters:
  • bqm (dimod.BinaryQuadraticModel) – Binary quadratic model (BQM).
  • sample (list/dict) – Sample values as returned by dimod samplers (0 or 1 values for dimod.BINARY and -1 or +1 for dimod.SPIN)
  • max_n (int, optional, default=None) – Maximum contributing variables to return. By default, returns any variable for which flipping its sample value results in an energy gain of min_gain.
  • min_gain (float, optional, default=None) – Minimum required energy increase from flipping a sample value to return its corresponding variable.
Returns:

Up to max_n variables for which flipping the corresponding sample value increases the BQM energy by at least min_gain.

Return type:

list

Examples

This example returns 2 variables (out of up to 3 allowed) for which flipping sample values changes BQM energy by 1 or more. The BQM has energy gains of 0, -2, 2, 4 for variables a, b, c, d respectively for the given sample.

>>> import dimod
>>> bqm = dimod.BQM({}, {'ab': 0, 'bc': 1, 'cd': 2}, 0, 'SPIN')
>>> select_localsearch_adversaries(
...     bqm, {'a': -1, 'b': 1, 'c': 1, 'd': -1}, max_n=3, min_gain=1)
['d', 'c']