mirror of
https://github.com/brycedrennan/imaginAIry
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236 lines
8.0 KiB
Python
236 lines
8.0 KiB
Python
# pylama:ignore=W0613
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import logging
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import numpy as np
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import torch
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from tqdm import tqdm
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from imaginairy.log_utils import increment_step, log_latent
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from imaginairy.modules.diffusion.util import extract_into_tensor, noise_like
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from imaginairy.samplers.base import (
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ImageSampler,
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NoiseSchedule,
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SamplerName,
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get_noise_prediction,
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mask_blend,
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)
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from imaginairy.utils import get_device
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logger = logging.getLogger(__name__)
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class PLMSSampler(ImageSampler):
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"""
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probabilistic least-mean-squares.
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Provenance:
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https://github.com/CompVis/latent-diffusion/commit/f0c4e092c156986e125f48c61a0edd38ba8ad059
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https://arxiv.org/abs/2202.09778
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https://github.com/luping-liu/PNDM
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"""
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short_name = SamplerName.PLMS
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name = "probabilistic least-mean-squares sampler"
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default_steps = 40
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@torch.no_grad()
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def sample(
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self,
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num_steps,
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shape,
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neutral_conditioning,
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positive_conditioning,
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guidance_scale=1.0,
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batch_size=1,
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mask=None,
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orig_latent=None,
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temperature=1.0,
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noise_dropout=0.0,
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initial_latent=None,
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t_start=None,
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quantize_denoised=False,
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**kwargs,
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):
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# if positive_conditioning.shape[0] != batch_size:
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# raise ValueError(
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# f"Got {positive_conditioning.shape[0]} conditionings but batch-size is {batch_size}"
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# )
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schedule = NoiseSchedule(
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model_num_timesteps=self.model.num_timesteps,
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ddim_num_steps=num_steps,
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model_alphas_cumprod=self.model.alphas_cumprod,
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ddim_discretize="uniform",
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)
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if initial_latent is None:
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initial_latent = torch.randn(shape, device="cpu").to(self.device)
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log_latent(initial_latent, "initial latent")
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timesteps = schedule.ddim_timesteps[:t_start]
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time_range = np.flip(timesteps)
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total_steps = timesteps.shape[0]
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old_eps = []
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noisy_latent = initial_latent
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mask_noise = None
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if mask is not None:
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mask_noise = torch.randn_like(noisy_latent, device="cpu").to(
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noisy_latent.device
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)
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for i, step in enumerate(tqdm(time_range, total=total_steps)):
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index = total_steps - i - 1
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ts = torch.full((batch_size,), step, device=self.device, dtype=torch.long)
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ts_next = torch.full(
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(batch_size,),
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time_range[min(i + 1, len(time_range) - 1)],
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device=self.device,
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dtype=torch.long,
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)
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if mask is not None:
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noisy_latent = mask_blend(
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noisy_latent=noisy_latent,
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orig_latent=orig_latent,
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mask=mask,
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mask_noise=mask_noise,
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ts=ts,
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model=self.model,
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)
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noisy_latent, predicted_latent, noise_pred = self.p_sample_plms(
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noisy_latent=noisy_latent,
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neutral_conditioning=neutral_conditioning,
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positive_conditioning=positive_conditioning,
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guidance_scale=guidance_scale,
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time_encoding=ts,
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schedule=schedule,
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index=index,
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quantize_denoised=quantize_denoised,
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temperature=temperature,
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noise_dropout=noise_dropout,
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old_eps=old_eps,
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t_next=ts_next,
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)
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old_eps.append(noise_pred)
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if len(old_eps) >= 4:
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old_eps.pop(0)
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log_latent(noisy_latent, "noisy_latent")
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log_latent(predicted_latent, "predicted_latent")
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increment_step()
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return noisy_latent
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@torch.no_grad()
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def p_sample_plms(
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self,
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noisy_latent,
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neutral_conditioning,
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positive_conditioning,
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guidance_scale,
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time_encoding,
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schedule: NoiseSchedule,
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index,
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repeat_noise=False,
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quantize_denoised=False,
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temperature=1.0,
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noise_dropout=0.0,
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old_eps=None,
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t_next=None,
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):
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assert guidance_scale >= 1
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noise_pred = get_noise_prediction(
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denoise_func=self.model.apply_model,
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noisy_latent=noisy_latent,
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time_encoding=time_encoding,
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neutral_conditioning=neutral_conditioning,
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positive_conditioning=positive_conditioning,
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signal_amplification=guidance_scale,
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)
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batch_size = noisy_latent.shape[0]
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def get_x_prev_and_pred_x0(e_t, index):
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# select parameters corresponding to the currently considered timestep
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alpha_at_t = torch.full(
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(batch_size, 1, 1, 1), schedule.ddim_alphas[index], device=self.device
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)
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alpha_prev_at_t = torch.full(
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(batch_size, 1, 1, 1),
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schedule.ddim_alphas_prev[index],
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device=self.device,
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)
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sigma_t = torch.full(
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(batch_size, 1, 1, 1), schedule.ddim_sigmas[index], device=self.device
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)
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sqrt_one_minus_at = torch.full(
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(batch_size, 1, 1, 1),
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schedule.ddim_sqrt_one_minus_alphas[index],
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device=self.device,
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)
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# current prediction for x_0
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pred_x0 = (noisy_latent - sqrt_one_minus_at * e_t) / alpha_at_t.sqrt()
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if quantize_denoised:
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pred_x0, _, *_ = self.model.first_stage_model.quantize(pred_x0)
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# direction pointing to x_t
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dir_xt = (1.0 - alpha_prev_at_t - sigma_t**2).sqrt() * e_t
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noise = (
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sigma_t
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* noise_like(noisy_latent.shape, self.device, repeat_noise)
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* temperature
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)
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if noise_dropout > 0.0:
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noise = torch.nn.functional.dropout(noise, p=noise_dropout)
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x_prev = alpha_prev_at_t.sqrt() * pred_x0 + dir_xt + noise
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return x_prev, pred_x0
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if len(old_eps) == 0:
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# Pseudo Improved Euler (2nd order)
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x_prev, pred_x0 = get_x_prev_and_pred_x0(noise_pred, index)
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e_t_next = get_noise_prediction(
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denoise_func=self.model.apply_model,
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noisy_latent=x_prev,
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time_encoding=t_next,
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neutral_conditioning=neutral_conditioning,
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positive_conditioning=positive_conditioning,
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signal_amplification=guidance_scale,
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)
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e_t_prime = (noise_pred + e_t_next) / 2
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elif len(old_eps) == 1:
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# 2nd order Pseudo Linear Multistep (Adams-Bashforth)
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e_t_prime = (3 * noise_pred - old_eps[-1]) / 2
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elif len(old_eps) == 2:
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# 3rd order Pseudo Linear Multistep (Adams-Bashforth)
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e_t_prime = (23 * noise_pred - 16 * old_eps[-1] + 5 * old_eps[-2]) / 12
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elif len(old_eps) >= 3:
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# 4nd order Pseudo Linear Multistep (Adams-Bashforth)
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e_t_prime = (
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55 * noise_pred - 59 * old_eps[-1] + 37 * old_eps[-2] - 9 * old_eps[-3]
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) / 24
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x_prev, pred_x0 = get_x_prev_and_pred_x0(e_t_prime, index)
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log_latent(x_prev, "x_prev")
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log_latent(pred_x0, "pred_x0")
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return x_prev, pred_x0, noise_pred
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@torch.no_grad()
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def noise_an_image(self, init_latent, t, schedule, noise=None):
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# fast, but does not allow for exact reconstruction
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# t serves as an index to gather the correct alphas
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t = t.clamp(0, 1000)
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sqrt_alphas_cumprod = torch.sqrt(schedule.ddim_alphas)
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sqrt_one_minus_alphas_cumprod = schedule.ddim_sqrt_one_minus_alphas
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if noise is None:
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noise = torch.randn_like(init_latent, device="cpu").to(get_device())
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return (
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extract_into_tensor(sqrt_alphas_cumprod, t, init_latent.shape) * init_latent
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+ extract_into_tensor(sqrt_one_minus_alphas_cumprod, t, init_latent.shape)
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* noise
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)
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