"""
Copyright 2013 Steven Diamond
This file is part of CVXPY.
CVXPY is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
CVXPY is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with CVXPY. If not, see <http://www.gnu.org/licenses/>.
"""
from .noncvx_variable import NonCvxVariable
import cvxpy as cvx
import numpy as np
class Integer(NonCvxVariable):
""" An integer variable. """
# M - upper bound on |x|
def __init__(self, rows=1, cols=1, M=None, *args, **kwargs):
if M is None or np.any(M <= 0):
raise Exception("Integer requires positive values for M.")
self.M = np.floor(M)
if np.isscalar(self.M) and (rows, cols) != (1,1):
self.M = self.M*np.ones((rows,cols))
super(Integer, self).__init__(rows, cols, *args, **kwargs)
def init_z(self, random):
"""Initializes the value of the replicant variable.
"""
self.z.value = np.zeros(self.shape)
# All values set rounded to the nearest integer.
def _project(self, matrix):
return np.around(matrix)
# Constrain all entries to be the value in the matrix.
def _restrict(self, matrix):
return [self == matrix]
def _neighbors(self, matrix):
neighbors_list = []
for i in range(self.shape[0]):
for j in range(self.shape[1]):
for diff in [1,-1]:
new_mat = matrix.copy()
new_mat[i,j] = new_mat[i,j] + diff
neighbors_list += [new_mat]
return neighbors_list
def relax(self):
return [cvx.abs(self) <= self.M]
