Source code for qlauncher.routines.dwave.algorithms

 1"""DWave algorithms"""
 2
 3from abc import ABC, abstractmethod
 4from typing import Any
 5
 6from qlauncher.base import Algorithm, Result
 7from qlauncher.base.models import BQM
 8from qlauncher.exceptions import DependencyError
 9from qlauncher.routines.dwave.backends import BQMBackend
10
11try:
12    from dimod import Sampler, SampleSet
13    from dwave.samplers import SimulatedAnnealingSampler, SteepestDescentSampler, TabuSampler
14except ImportError as e:
15    raise DependencyError(e, install_hint='dwave') from e
16
17

[docs]
18class DwaveSolver(Algorithm[BQM, BQMBackend], ABC):
19    def __init__(self, chain_strength: int = 1, num_reads: int = 1000, **alg_kwargs) -> None:
20        self.chain_strength = chain_strength
21        self.num_reads = num_reads
22        self.label: str = 'TBD_TBD'
23        super().__init__(**alg_kwargs)
24

[docs]
25    def run(self, problem: BQM, backend: BQMBackend) -> Result:
26        res = self._solve_bqm(problem.bqm, self._get_sampler(), **self.alg_kwargs)
27        return self._construct_result(res)

28
29    def _solve_bqm(self, bqm: Any, sampler: Sampler, **kwargs) -> SampleSet:
30        return sampler.sample(bqm, num_reads=self.num_reads, label=self.label, chain_strength=self.chain_strength, **kwargs)
31
32    @abstractmethod
33    def _get_sampler(self) -> Sampler:
34        pass
35
36    def _construct_result(self, result: SampleSet) -> Result:
37        distribution = {}
38        energies = {}
39        for value, energy, occ in zip(result.record.sample, result.record.energy, result.record.num_occurrences, strict=True):
40            bitstring = ''.join(map(str, value))
41            if bitstring in distribution:
42                distribution[bitstring] += occ
43                continue
44            distribution[bitstring] = occ
45            energies[bitstring] = energy
46
47        return Result.from_counts_energies(distribution, energies, result)

48
49

[docs]
50class Tabu(DwaveSolver):
51    """Tabu search simulator backend"""
52
53    def _get_sampler(self) -> Sampler:
54        return TabuSampler()

55
56

[docs]
57class SimulatedAnnealing(DwaveSolver):
58    """Simulated annealing simulator backend"""
59
60    def _get_sampler(self) -> Sampler:
61        return SimulatedAnnealingSampler()

62
63

[docs]
64class SteepestDescent(DwaveSolver):
65    """Steepest descent simulator backend"""
66
67    def _get_sampler(self) -> Sampler:
68        return SteepestDescentSampler()