Source code for

from __future__ import absolute_import, division, print_function

import torch.nn.functional as F

import pyro
import pyro.distributions as dist

from .likelihood import Likelihood

[docs]class Binary(Likelihood): """ Implementation of Binary likelihood, which is used for binary classification problems. Binary likelihood uses :class:`~pyro.distributions.Bernoulli` distribution, so the output of ``response_function`` should be in range :math:`(0,1)`. By default, we use `sigmoid` function. :param callable response_function: A mapping to correct domain for Binary likelihood. """ def __init__(self, response_function=None, name="Binary"): super(Binary, self).__init__(name) self.response_function = (response_function if response_function is not None else F.sigmoid)
[docs] def forward(self, f_loc, f_var, y=None): r""" Samples :math:`y` given :math:`f_{loc}`, :math:`f_{var}` according to .. math:: f & \sim \mathbb{Normal}(f_{loc}, f_{var}),\\ y & \sim \mathbb{Bernoulli}(f). .. note:: The log likelihood is estimated using Monte Carlo with 1 sample of :math:`f`. :param torch.Tensor f_loc: Mean of latent function output. :param torch.Tensor f_var: Variance of latent function output. :param torch.Tensor y: Training output tensor. :returns: a tensor sampled from likelihood :rtype: torch.Tensor """ # calculates Monte Carlo estimate for E_q(f) [logp(y | f)] f = dist.Normal(f_loc, f_var)() f_res = self.response_function(f) y_dist = dist.Bernoulli(f_res) if y is not None: y_dist = y_dist.expand_by(y.shape[:-f_res.dim()]).independent(y.dim()) return pyro.sample(self.y_name, y_dist, obs=y)