82 lines
3.3 KiB
Python
82 lines
3.3 KiB
Python
import torch
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import torch.nn as nn
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import numpy as np
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from functools import partial
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from .util import extract_into_tensor, make_beta_schedule
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from fcbh.ldm.util import default
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class AbstractLowScaleModel(nn.Module):
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# for concatenating a downsampled image to the latent representation
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def __init__(self, noise_schedule_config=None):
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super(AbstractLowScaleModel, self).__init__()
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if noise_schedule_config is not None:
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self.register_schedule(**noise_schedule_config)
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def register_schedule(self, beta_schedule="linear", timesteps=1000,
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linear_start=1e-4, linear_end=2e-2, cosine_s=8e-3):
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betas = make_beta_schedule(beta_schedule, timesteps, linear_start=linear_start, linear_end=linear_end,
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cosine_s=cosine_s)
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alphas = 1. - betas
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alphas_cumprod = np.cumprod(alphas, axis=0)
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alphas_cumprod_prev = np.append(1., alphas_cumprod[:-1])
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timesteps, = betas.shape
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self.num_timesteps = int(timesteps)
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self.linear_start = linear_start
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self.linear_end = linear_end
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assert alphas_cumprod.shape[0] == self.num_timesteps, 'alphas have to be defined for each timestep'
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to_torch = partial(torch.tensor, dtype=torch.float32)
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self.register_buffer('betas', to_torch(betas))
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self.register_buffer('alphas_cumprod', to_torch(alphas_cumprod))
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self.register_buffer('alphas_cumprod_prev', to_torch(alphas_cumprod_prev))
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# calculations for diffusion q(x_t | x_{t-1}) and others
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self.register_buffer('sqrt_alphas_cumprod', to_torch(np.sqrt(alphas_cumprod)))
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self.register_buffer('sqrt_one_minus_alphas_cumprod', to_torch(np.sqrt(1. - alphas_cumprod)))
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self.register_buffer('log_one_minus_alphas_cumprod', to_torch(np.log(1. - alphas_cumprod)))
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self.register_buffer('sqrt_recip_alphas_cumprod', to_torch(np.sqrt(1. / alphas_cumprod)))
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self.register_buffer('sqrt_recipm1_alphas_cumprod', to_torch(np.sqrt(1. / alphas_cumprod - 1)))
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def q_sample(self, x_start, t, noise=None):
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noise = default(noise, lambda: torch.randn_like(x_start))
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return (extract_into_tensor(self.sqrt_alphas_cumprod, t, x_start.shape) * x_start +
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extract_into_tensor(self.sqrt_one_minus_alphas_cumprod, t, x_start.shape) * noise)
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def forward(self, x):
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return x, None
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def decode(self, x):
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return x
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class SimpleImageConcat(AbstractLowScaleModel):
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# no noise level conditioning
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def __init__(self):
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super(SimpleImageConcat, self).__init__(noise_schedule_config=None)
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self.max_noise_level = 0
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def forward(self, x):
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# fix to constant noise level
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return x, torch.zeros(x.shape[0], device=x.device).long()
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class ImageConcatWithNoiseAugmentation(AbstractLowScaleModel):
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def __init__(self, noise_schedule_config, max_noise_level=1000, to_cuda=False):
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super().__init__(noise_schedule_config=noise_schedule_config)
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self.max_noise_level = max_noise_level
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def forward(self, x, noise_level=None):
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if noise_level is None:
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noise_level = torch.randint(0, self.max_noise_level, (x.shape[0],), device=x.device).long()
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else:
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assert isinstance(noise_level, torch.Tensor)
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z = self.q_sample(x, noise_level)
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return z, noise_level
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