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# Modified from OpenAI's diffusion repos | |
# GLIDE: https://github.com/openai/glide-text2im/blob/main/glide_text2im/gaussian_diffusion.py | |
# ADM: https://github.com/openai/guided-diffusion/blob/main/guided_diffusion | |
# IDDPM: https://github.com/openai/improved-diffusion/blob/main/improved_diffusion/gaussian_diffusion.py | |
from . import gaussian_diffusion as gd | |
from .respace import SpacedDiffusion, space_timesteps | |
def create_diffusion( | |
timestep_respacing, | |
noise_schedule="linear", | |
use_kl=False, | |
sigma_small=False, | |
predict_xstart=False, | |
learn_sigma=True, | |
rescale_learned_sigmas=False, | |
diffusion_steps=1000 | |
): | |
betas = gd.get_named_beta_schedule(noise_schedule, diffusion_steps) | |
if use_kl: | |
loss_type = gd.LossType.RESCALED_KL | |
elif rescale_learned_sigmas: | |
loss_type = gd.LossType.RESCALED_MSE | |
else: | |
loss_type = gd.LossType.MSE | |
if timestep_respacing is None or timestep_respacing == "": | |
timestep_respacing = [diffusion_steps] | |
return SpacedDiffusion( | |
use_timesteps=space_timesteps(diffusion_steps, timestep_respacing), | |
betas=betas, | |
model_mean_type=( | |
gd.ModelMeanType.EPSILON if not predict_xstart else gd.ModelMeanType.START_X | |
), | |
model_var_type=( | |
( | |
gd.ModelVarType.FIXED_LARGE | |
if not sigma_small | |
else gd.ModelVarType.FIXED_SMALL | |
) | |
if not learn_sigma | |
else gd.ModelVarType.LEARNED_RANGE | |
), | |
loss_type=loss_type | |
# rescale_timesteps=rescale_timesteps, | |
) | |