Source code for qlauncher.routines.dwave.algorithms

 1"""DWave algorithms"""
 2
 3from collections.abc import Callable
 4
 5from qlauncher.base import Algorithm, Problem, Result
 6from qlauncher.exceptions import DependencyError
 7from qlauncher.routines.dwave.backends import BQMBackend
 8try:
 9    from dimod.binary.binary_quadratic_model import BinaryQuadraticModel
10    from dimod import SampleSet
11except ImportError as e:
12    raise DependencyError(e, install_hint='dwave') from e
13
14

[docs]
15class DwaveSolver(Algorithm):
16    _algorithm_format = 'bqm'
17
18    def __init__(self, chain_strength=1, num_reads=1000, **alg_kwargs) -> None:
19        self.chain_strength = chain_strength
20        self.num_reads = num_reads
21        self.label: str = 'TBD_TBD'
22        super().__init__(**alg_kwargs)
23

[docs]
24    def run(self, problem: Problem, backend: BQMBackend, formatter: Callable) -> Result:
25        self.label = f'{problem.name}_{problem.instance_name}'
26
27        bqm: BinaryQuadraticModel = formatter(problem)
28
29        res = self._solve_bqm(bqm, backend.sampler, **self.alg_kwargs)
30        return self._construct_result(res)

31
32    def _solve_bqm(self, bqm, sampler, **kwargs):
33        res = sampler.sample(
34            bqm, num_reads=self.num_reads, label=self.label, chain_strength=self.chain_strength, **kwargs)
35        return res
36
37    def _construct_result(self, result: SampleSet) -> Result:
38        distribution = {}
39        energies = {}
40        for (value, energy, occ) in zip(result.record.sample, result.record.energy, result.record.num_occurrences, strict=True):
41            bitstring = ''.join(map(str, value))
42            if bitstring in distribution:
43                distribution[bitstring] += occ
44                continue
45            distribution[bitstring] = occ
46            energies[bitstring] = energy
47
48        return Result.from_distributions(distribution, energies, result)