Source code for pyro.infer.reparam.discrete_cosine

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

from pyro.distributions.transforms.discrete_cosine import DiscreteCosineTransform

from .unit_jacobian import UnitJacobianReparam

[docs]class DiscreteCosineReparam(UnitJacobianReparam): """ Discrete Cosine reparameterizer, using a :class:`~pyro.distributions.transforms.DiscreteCosineTransform` . This is useful for sequential models where coupling along a time-like axis (e.g. a banded precision matrix) introduces long-range correlation. This reparameterizes to a frequency-domain representation where posterior covariance should be closer to diagonal, thereby improving the accuracy of diagonal guides in SVI and improving the effectiveness of a diagonal mass matrix in HMC. When reparameterizing variables that are approximately continuous along the time dimension, set ``smooth=1``. For variables that are approximately continuously differentiable along the time axis, set ``smooth=2``. This reparameterization works only for latent variables, not likelihoods. :param int dim: Dimension along which to transform. Must be negative. This is an absolute dim counting from the right. :param float smooth: Smoothing parameter. When 0, this transforms white noise to white noise; when 1 this transforms Brownian noise to to white noise; when -1 this transforms violet noise to white noise; etc. Any real number is allowed. """ def __init__(self, dim=-1, smooth=0., *, experimental_allow_batch=False): transform = DiscreteCosineTransform(dim=dim, smooth=smooth, cache_size=1) super().__init__(transform, suffix="dct", experimental_allow_batch=experimental_allow_batch)