Source code for qlauncher.problems.problem_formulations.bqm

 1import ast
 2import numpy as np
 3from pyqubo import Spin
 4from qlauncher.base import adapter, formatter
 5from qlauncher.problems.problem_initialization import Raw
 6
 7


[docs]
 8@adapter('qubo', 'bqm')
 9def qubo_to_bqm(qubo_with_offset) -> dict:
10    qubo, offset = qubo_with_offset
11    bqm, _ = QUBOMatrix(qubo, offset).qubo_matrix_into_bqm()
12    return bqm


13
14


[docs]
15class QUBOMatrix:
16    def __init__(self, qubo_matrix, offset):
17        self.qubo_matrix = qubo_matrix
18        self.offset = offset
19
20        if type(self.qubo_matrix) == str:
21            self.qubo_matrix = np.array(ast.literal_eval(self.qubo_matrix))
22
23        self.symetric = True
24        self._check_if_symetric()
25
26    def _check_if_symetric(self):
27        """
28        Function to check if matrix is symetric
29        """
30        self.symetric = (self.qubo_matrix.transpose()
31                         == self.qubo_matrix).all()
32        if not self.symetric:
33            self.qubo_matrix = self._remove_lower_triangle(self.qubo_matrix)
34
35    def _remove_lower_triangle(self, matrix):
36        """
37        Function to remove lower triangle from matrix
38        """
39        for i in range(len(matrix)):
40            for j in range(len(matrix)):
41                if i > j:
42                    matrix[i][j] = 0
43        return matrix
44
45    def _get_values_and_qubits(self, matrix):
46        """
47        Function to get values and qubits from matrix in form of dictionary
48        where keys are indexes of qubits and values are values of matrix
49        The function does not take into account zeros in matrix
50        Example:
51        matrix = [[0,1,2],[1,0,3],[2,3,0]]
52        result = {(0,1):1, (0,2):2, (1,0):1, (1,2):3, (2,0):2, (2,1):3}
53        Function also return second value which is the number of qubits
54        """
55        result = {
56            (x, y): c for y, r in enumerate(matrix) for x, c in enumerate(r) if c != 0
57        }
58        return result, len(matrix)
59


[docs]
60    def qubo_matrix_into_bqm(self):
61        values_and_qubits, number_of_qubits = self._get_values_and_qubits(
62            self.qubo_matrix
63        )
64        qubits = [Spin(f"x{i}") for i in range(number_of_qubits)]
65        H = 0
66        for (x, y), value in values_and_qubits.items():
67            if self.symetric:
68                H += value / len(set((x, y))) * qubits[x] * qubits[y]
69            else:
70                H += value * qubits[x] * qubits[y]
71        model = H.compile()
72        bqm = model.to_bqm()
73        bqm.offset += self.offset
74        return bqm, model




75
76


[docs]
77@formatter(Raw, 'bqm')
78def Rawbqm(problem: Raw):
79    return problem.instance