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# Copyright 2023 Stanford University Team and The HuggingFace Team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# DISCLAIMER: This code is strongly influenced by https://github.com/pesser/pytorch_diffusion
# and https://github.com/hojonathanho/diffusion
from __future__ import annotations
import math
from dataclasses import dataclass
from typing import List, Optional, Tuple, Union
import numpy as np
import torch
from numpy import ndarray
from diffusers.configuration_utils import ConfigMixin, register_to_config
from diffusers.utils import BaseOutput, logging
from diffusers.utils.torch_utils import randn_tensor
from diffusers.schedulers.scheduling_utils import SchedulerMixin
from diffusers.schedulers.scheduling_lcm import (
LCMSchedulerOutput,
betas_for_alpha_bar,
rescale_zero_terminal_snr,
LCMScheduler as DiffusersLCMScheduler,
)
from ..utils.noise_util import video_fusion_noise
logger = logging.get_logger(__name__) # pylint: disable=invalid-name
class LCMScheduler(DiffusersLCMScheduler):
def __init__(
self,
num_train_timesteps: int = 1000,
beta_start: float = 0.00085,
beta_end: float = 0.012,
beta_schedule: str = "scaled_linear",
trained_betas: ndarray | List[float] | None = None,
original_inference_steps: int = 50,
clip_sample: bool = False,
clip_sample_range: float = 1,
set_alpha_to_one: bool = True,
steps_offset: int = 0,
prediction_type: str = "epsilon",
thresholding: bool = False,
dynamic_thresholding_ratio: float = 0.995,
sample_max_value: float = 1,
timestep_spacing: str = "leading",
timestep_scaling: float = 10,
rescale_betas_zero_snr: bool = False,
):
super().__init__(
num_train_timesteps,
beta_start,
beta_end,
beta_schedule,
trained_betas,
original_inference_steps,
clip_sample,
clip_sample_range,
set_alpha_to_one,
steps_offset,
prediction_type,
thresholding,
dynamic_thresholding_ratio,
sample_max_value,
timestep_spacing,
timestep_scaling,
rescale_betas_zero_snr,
)
def step(
self,
model_output: torch.FloatTensor,
timestep: int,
sample: torch.FloatTensor,
generator: Optional[torch.Generator] = None,
return_dict: bool = True,
w_ind_noise: float = 0.5,
noise_type: str = "random",
) -> Union[LCMSchedulerOutput, Tuple]:
"""
Predict the sample from the previous timestep by reversing the SDE. This function propagates the diffusion
process from the learned model outputs (most often the predicted noise).
Args:
model_output (`torch.FloatTensor`):
The direct output from learned diffusion model.
timestep (`float`):
The current discrete timestep in the diffusion chain.
sample (`torch.FloatTensor`):
A current instance of a sample created by the diffusion process.
generator (`torch.Generator`, *optional*):
A random number generator.
return_dict (`bool`, *optional*, defaults to `True`):
Whether or not to return a [`~schedulers.scheduling_lcm.LCMSchedulerOutput`] or `tuple`.
Returns:
[`~schedulers.scheduling_utils.LCMSchedulerOutput`] or `tuple`:
If return_dict is `True`, [`~schedulers.scheduling_lcm.LCMSchedulerOutput`] is returned, otherwise a
tuple is returned where the first element is the sample tensor.
"""
if self.num_inference_steps is None:
raise ValueError(
"Number of inference steps is 'None', you need to run 'set_timesteps' after creating the scheduler"
)
if self.step_index is None:
self._init_step_index(timestep)
# 1. get previous step value
prev_step_index = self.step_index + 1
if prev_step_index < len(self.timesteps):
prev_timestep = self.timesteps[prev_step_index]
else:
prev_timestep = timestep
# 2. compute alphas, betas
alpha_prod_t = self.alphas_cumprod[timestep]
alpha_prod_t_prev = (
self.alphas_cumprod[prev_timestep]
if prev_timestep >= 0
else self.final_alpha_cumprod
)
beta_prod_t = 1 - alpha_prod_t
beta_prod_t_prev = 1 - alpha_prod_t_prev
# 3. Get scalings for boundary conditions
c_skip, c_out = self.get_scalings_for_boundary_condition_discrete(timestep)
# 4. Compute the predicted original sample x_0 based on the model parameterization
if self.config.prediction_type == "epsilon": # noise-prediction
predicted_original_sample = (
sample - beta_prod_t.sqrt() * model_output
) / alpha_prod_t.sqrt()
elif self.config.prediction_type == "sample": # x-prediction
predicted_original_sample = model_output
elif self.config.prediction_type == "v_prediction": # v-prediction
predicted_original_sample = (
alpha_prod_t.sqrt() * sample - beta_prod_t.sqrt() * model_output
)
else:
raise ValueError(
f"prediction_type given as {self.config.prediction_type} must be one of `epsilon`, `sample` or"
" `v_prediction` for `LCMScheduler`."
)
# 5. Clip or threshold "predicted x_0"
if self.config.thresholding:
predicted_original_sample = self._threshold_sample(
predicted_original_sample
)
elif self.config.clip_sample:
predicted_original_sample = predicted_original_sample.clamp(
-self.config.clip_sample_range, self.config.clip_sample_range
)
# 6. Denoise model output using boundary conditions
denoised = c_out * predicted_original_sample + c_skip * sample
# 7. Sample and inject noise z ~ N(0, I) for MultiStep Inference
# Noise is not used on the final timestep of the timestep schedule.
# This also means that noise is not used for one-step sampling.
device = model_output.device
if self.step_index != self.num_inference_steps - 1:
if noise_type == "random":
noise = randn_tensor(
model_output.shape,
dtype=model_output.dtype,
device=device,
generator=generator,
)
elif noise_type == "video_fusion":
noise = video_fusion_noise(
model_output, w_ind_noise=w_ind_noise, generator=generator
)
prev_sample = (
alpha_prod_t_prev.sqrt() * denoised + beta_prod_t_prev.sqrt() * noise
)
else:
prev_sample = denoised
# upon completion increase step index by one
self._step_index += 1
if not return_dict:
return (prev_sample, denoised)
return LCMSchedulerOutput(prev_sample=prev_sample, denoised=denoised)
def step_bk(
self,
model_output: torch.FloatTensor,
timestep: int,
sample: torch.FloatTensor,
generator: Optional[torch.Generator] = None,
return_dict: bool = True,
) -> Union[LCMSchedulerOutput, Tuple]:
"""
Predict the sample from the previous timestep by reversing the SDE. This function propagates the diffusion
process from the learned model outputs (most often the predicted noise).
Args:
model_output (`torch.FloatTensor`):
The direct output from learned diffusion model.
timestep (`float`):
The current discrete timestep in the diffusion chain.
sample (`torch.FloatTensor`):
A current instance of a sample created by the diffusion process.
generator (`torch.Generator`, *optional*):
A random number generator.
return_dict (`bool`, *optional*, defaults to `True`):
Whether or not to return a [`~schedulers.scheduling_lcm.LCMSchedulerOutput`] or `tuple`.
Returns:
[`~schedulers.scheduling_utils.LCMSchedulerOutput`] or `tuple`:
If return_dict is `True`, [`~schedulers.scheduling_lcm.LCMSchedulerOutput`] is returned, otherwise a
tuple is returned where the first element is the sample tensor.
"""
if self.num_inference_steps is None:
raise ValueError(
"Number of inference steps is 'None', you need to run 'set_timesteps' after creating the scheduler"
)
if self.step_index is None:
self._init_step_index(timestep)
# 1. get previous step value
prev_step_index = self.step_index + 1
if prev_step_index < len(self.timesteps):
prev_timestep = self.timesteps[prev_step_index]
else:
prev_timestep = timestep
# 2. compute alphas, betas
alpha_prod_t = self.alphas_cumprod[timestep]
alpha_prod_t_prev = (
self.alphas_cumprod[prev_timestep]
if prev_timestep >= 0
else self.final_alpha_cumprod
)
beta_prod_t = 1 - alpha_prod_t
beta_prod_t_prev = 1 - alpha_prod_t_prev
# 3. Get scalings for boundary conditions
c_skip, c_out = self.get_scalings_for_boundary_condition_discrete(timestep)
# 4. Compute the predicted original sample x_0 based on the model parameterization
if self.config.prediction_type == "epsilon": # noise-prediction
predicted_original_sample = (
sample - beta_prod_t.sqrt() * model_output
) / alpha_prod_t.sqrt()
elif self.config.prediction_type == "sample": # x-prediction
predicted_original_sample = model_output
elif self.config.prediction_type == "v_prediction": # v-prediction
predicted_original_sample = (
alpha_prod_t.sqrt() * sample - beta_prod_t.sqrt() * model_output
)
else:
raise ValueError(
f"prediction_type given as {self.config.prediction_type} must be one of `epsilon`, `sample` or"
" `v_prediction` for `LCMScheduler`."
)
# 5. Clip or threshold "predicted x_0"
if self.config.thresholding:
predicted_original_sample = self._threshold_sample(
predicted_original_sample
)
elif self.config.clip_sample:
predicted_original_sample = predicted_original_sample.clamp(
-self.config.clip_sample_range, self.config.clip_sample_range
)
# 6. Denoise model output using boundary conditions
denoised = c_out * predicted_original_sample + c_skip * sample
# 7. Sample and inject noise z ~ N(0, I) for MultiStep Inference
# Noise is not used on the final timestep of the timestep schedule.
# This also means that noise is not used for one-step sampling.
if self.step_index != self.num_inference_steps - 1:
noise = randn_tensor(
model_output.shape,
generator=generator,
device=model_output.device,
dtype=denoised.dtype,
)
prev_sample = (
alpha_prod_t_prev.sqrt() * denoised + beta_prod_t_prev.sqrt() * noise
)
else:
prev_sample = denoised
# upon completion increase step index by one
self._step_index += 1
if not return_dict:
return (prev_sample, denoised)
return LCMSchedulerOutput(prev_sample=prev_sample, denoised=denoised)
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