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e12111a | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 | """Utility functions for diffusion models."""
from __future__ import annotations
import jax.numpy as jnp
def extract_and_expand(arr: jnp.ndarray, t_index: jnp.ndarray, ndim: int) -> jnp.ndarray:
"""Extract values from a 1D array and expand.
This function is not jittable.
Args:
arr: 1D of shape (num_timesteps, ).
t_index: storing index values < self.num_timesteps,
shape (batch, ) or has ndim dimension.
ndim: number of dimensions for an array of shape (batch, ...).
Returns:
Expanded array of shape (batch, ...), expanded axes have dim 1.
"""
if arr.ndim != 1:
raise ValueError(f"arr must be 1D, got {arr.ndim}D.")
x = arr[t_index]
return expand(x, ndim)
def expand(x: jnp.ndarray, ndim: int) -> jnp.ndarray:
"""Expand.
This function is not jittable.
Args:
x: a 1D or nD array.
ndim: number of dimensions as output.
Returns:
Expanded array, expanded axes have dim 1.
"""
if x.ndim == 1:
return jnp.expand_dims(x, axis=tuple(range(1, ndim)))
if x.ndim == ndim:
return x
raise ValueError(f"t_index must be 1D or {ndim}D, got {x.ndim}D.")
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