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Running
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Zero
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from diffusers import LCMScheduler
from diffusers.utils import BaseOutput
from diffusers.utils.torch_utils import randn_tensor
import torch
from typing import List, Optional, Tuple, Union
import numpy as np
class LCMSchedulerOutput(BaseOutput):
"""
Output class for the scheduler's `step` function output.
Args:
prev_sample (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)` for images):
Computed sample `(x_{t-1})` of previous timestep. `prev_sample` should be used as next model input in the
denoising loop.
pred_original_sample (`torch.FloatTensor` of shape `(batch_size, num_channels, height, width)` for images):
The predicted denoised sample `(x_{0})` based on the model output from the current timestep.
`pred_original_sample` can be used to preview progress or for guidance.
"""
prev_sample: torch.FloatTensor
denoised: Optional[torch.FloatTensor] = None
class MyLCMScheduler(LCMScheduler):
def set_noise_list(self, noise_list):
self.noise_list = noise_list
def step(
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"
)
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 = self.noise_list[self.step_index]
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 inv_step(
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"
)
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)
if self.step_index != self.num_inference_steps - 1:
c_skip_actual = c_skip * alpha_prod_t_prev.sqrt()
c_out_actual = c_out * alpha_prod_t_prev.sqrt()
noise = self.noise_list[self.step_index] * beta_prod_t_prev.sqrt()
else:
c_skip_actual = c_skip
c_out_actual = c_out
noise = 0
dem = c_out_actual / (alpha_prod_t.sqrt()) + c_skip
eps_mul = beta_prod_t.sqrt() * c_out_actual / (alpha_prod_t.sqrt())
prev_sample = (sample + eps_mul * model_output - noise) / dem
# upon completion increase step index by one
self._step_index += 1
if not return_dict:
return (prev_sample, prev_sample)
return LCMSchedulerOutput(prev_sample=prev_sample, denoised=prev_sample) |