Source code for pyro.distributions.transforms.ordered

# Copyright Contributors to the Pyro project.
# SPDX-License-Identifier: Apache-2.0

import torch
from torch.distributions.transforms import Transform

from .. import constraints

[docs]class OrderedTransform(Transform): """ Transforms a real vector into an ordered vector. Specifically, enforces monotonically increasing order on the last dimension of a given tensor via the transformation :math:`y_0 = x_0`, :math:`y_i = \\sum_{1 \\le j \\le i} \\exp(x_i)` """ domain = constraints.real_vector codomain = constraints.ordered_vector bijective = True def _call(self, x): z =[x[..., :1], x[..., 1:].exp()], dim=-1) return torch.cumsum(z, dim=-1) def _inverse(self, y): x = (y[..., 1:] - y[..., :-1]).log() return[y[..., :1], x], dim=-1)
[docs] def log_abs_det_jacobian(self, x, y): return torch.sum(x[..., 1:], dim=-1)