Source code for cvxpy.atoms.affine.kron

Copyright 2013 Steven Diamond

This file is part of CVXPY.

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from cvxpy.atoms.affine.affine_atom import AffAtom
import cvxpy.utilities as u
import cvxpy.lin_ops.lin_utils as lu
import numpy as np

[docs]class kron(AffAtom): """Kronecker product. """ # TODO work with right hand constant. def __init__(self, lh_expr, rh_expr): super(kron, self).__init__(lh_expr, rh_expr) @AffAtom.numpy_numeric def numeric(self, values): """Kronecker product of the two values. """ return np.kron(values[0], values[1]) def validate_arguments(self): """Checks that both arguments are vectors, and the first is constant. """ if not self.args[0].is_constant(): raise ValueError("The first argument to kron must be constant.") elif self.args[0].ndim != 2 or self.args[1].ndim != 2: raise ValueError("kron requires matrix arguments.") def shape_from_args(self): """The sum of the argument dimensions - 1. """ rows = self.args[0].shape[0]*self.args[1].shape[0] cols = self.args[0].shape[1]*self.args[1].shape[1] return (rows, cols) def sign_from_args(self): """Same as times. """ return u.sign.mul_sign(self.args[0], self.args[1]) def is_incr(self, idx): """Is the composition non-decreasing in argument idx? """ return self.args[0].is_nonneg() def is_decr(self, idx): """Is the composition non-increasing in argument idx? """ return self.args[0].is_nonpos() @staticmethod def graph_implementation(arg_objs, shape, data=None): """Kronecker product of two matrices. Parameters ---------- arg_objs : list LinOp for each argument. shape : tuple The shape of the resulting expression. data : Additional data required by the atom. Returns ------- tuple (LinOp for objective, list of constraints) """ return (lu.kron(arg_objs[0], arg_objs[1], shape), [])