48 lines
1.3 KiB
Python
48 lines
1.3 KiB
Python
import math
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from collections.abc import Callable
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import torch
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from torch import Tensor
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def get_noise(num_samples: int, height: int, width: int, device: torch.device, dtype: torch.dtype, seed: int):
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return torch.randn(
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num_samples,
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16,
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# allow for packing
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2 * math.ceil(height / 16),
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2 * math.ceil(width / 16),
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device=device,
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dtype=dtype,
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generator=torch.Generator(device=device).manual_seed(seed),
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)
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def time_shift(mu: float, sigma: float, t: Tensor):
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return math.exp(mu) / (math.exp(mu) + (1 / t - 1) ** sigma)
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def get_lin_function(x1: float = 256, y1: float = 0.5, x2: float = 4096, y2: float = 1.15) -> Callable[[float], float]:
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m = (y2 - y1) / (x2 - x1)
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b = y1 - m * x1
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return lambda x: m * x + b
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def get_schedule(
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num_steps: int,
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image_seq_len: int,
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base_shift: float = 0.5,
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max_shift: float = 1.15,
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shift: bool = True,
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) -> list[float]:
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# extra step for zero
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timesteps = torch.linspace(1, 0, num_steps + 1)
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# shifting the schedule to favor high timesteps for higher signal images
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if shift:
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# estimate mu based on linear estimation between two points
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mu = get_lin_function(y1=base_shift, y2=max_shift)(image_seq_len)
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timesteps = time_shift(mu, 1.0, timesteps)
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return timesteps.tolist()
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