Source code for openjij.sampler.csqa_sampler

import numpy as np
import openjij
from openjij.sampler import measure_time
from openjij.sampler import SQASampler
from openjij.utils.decorator import deprecated_alias
import cxxjij

[docs]class CSQASampler(SQASampler): """Sampler with continuous-time simulated quantum annealing (CSQA) using Hamiltonian .. math:: H(s) = s H_p + \\Gamma (1-s)\\sum_i \\sigma_i^x where :math:`H_p` is the problem Hamiltonian we want to solve. Args: beta (float): Inverse temperature. gamma (float): Amplitude of quantum fluctuation. schedule (list): schedule list step_num (int): Number of Monte Carlo step. schedule_info (dict): Information about a annealing schedule. num_reads (int): Number of iterations. num_sweeps (int): number of sweeps num_reads (int): Number of iterations. schedule_info (dict): Information about a annealing schedule. """ def __init__(self, beta=5.0, gamma=1.0, num_sweeps=1000, schedule=None, num_reads=1): self.beta = beta self.gamma = gamma self.num_reads = num_reads self.num_sweeps = num_sweeps self.schedule = schedule self.energy_bias = 0.0 self._schedule_setting = { 'beta': beta, 'gamma': gamma, 'num_sweeps': num_sweeps, 'num_reads': num_reads, } def _get_result(self, system, model): info = {} info['spin_config'] = system.spin_config state = cxxjij.result.get_solution(system) return state, info
[docs] def sample_ising(self, h, J, beta=None, gamma=None, num_sweeps=None, schedule=None, num_reads=1, initial_state=None, updater='swendsenwang', reinitialize_state=True, seed=None): """Sampling from the Ising model. Args: h (dict): linear biases J (dict): quadratic biases beta (float, optional): inverse temperature gamma (float, optional): strength of transverse field num_sweeps (int, optional): number of sampling. schedule (list, optional): schedule list num_reads (int, optional): number of iterations initial_state (optional): initial state of spins updater (str, optional): updater algorithm reinitialize_state (bool, optional): Re-initilization at each sampling. Defaults to True. seed (int, optional): Sampling seed. structure (int, optional): specify the structure. This argument is necessary if the model has a specific structure (e.g. Chimera graph) and the updater algorithm is structure-dependent. structure must have two types of keys, namely "size" which shows the total size of spins and "dict" which is the map from model index (elements in model.indices) to the number. Returns: :class:`openjij.sampler.response.Response`: results Examples: for Ising case:: >>> h = {0: -1, 1: -1, 2: 1, 3: 1} >>> J = {(0, 1): -1, (3, 4): -1} >>> sampler = oj.CSQASampler() >>> res = sampler.sample_ising(h, J) for QUBO case:: >>> Q = {(0, 0): -1, (1, 1): -1, (2, 2): 1, (3, 3): 1, (4, 4): 1, (0, 1): -1, (3, 4): 1} >>> sampler = oj.CSQASampler() >>> res = sampler.sample_qubo(Q) """ bqm = openjij.BinaryQuadraticModel( linear=h, quadratic=J, var_type='SPIN' ) #Continuous time ising system only supports sparse ising graph ising_graph = bqm.get_cxxjij_ising_graph(sparse=True) self._setting_overwrite( beta=beta, gamma=gamma, num_sweeps=num_sweeps, num_reads=num_reads ) self._annealing_schedule_setting( bqm, beta, gamma, num_sweeps, schedule) # make init state generator -------------------------------- if initial_state is None: def init_generator(): spin_config = np.random.choice([1,-1], len(bqm.indices)) return list(spin_config) else: def init_generator(): return initial_state # -------------------------------- make init state generator # choose updater ------------------------------------------- sqa_system = cxxjij.system.make_continuous_time_ising( init_generator(), ising_graph, self.gamma ) _updater_name = updater.lower().replace('_', '').replace(' ', '') if _updater_name == 'swendsenwang': algorithm = cxxjij.algorithm.Algorithm_ContinuousTimeSwendsenWang_run else: raise ValueError('updater is one of "swendsen wang"') # ------------------------------------------- choose updater response = self._cxxjij_sampling( bqm, init_generator, algorithm, sqa_system, reinitialize_state, seed )['schedule'] = self.schedule_info return response