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91 lines
2.8 KiB
91 lines
2.8 KiB
2 years ago
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from typing import Any, Callable, Dict, Optional
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import torch
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import torch.nn as nn
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from .gaussian_diffusion import GaussianDiffusion
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from .k_diffusion import karras_sample
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DEFAULT_KARRAS_STEPS = 64
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DEFAULT_KARRAS_SIGMA_MIN = 1e-3
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DEFAULT_KARRAS_SIGMA_MAX = 160
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DEFAULT_KARRAS_S_CHURN = 0.0
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def uncond_guide_model(
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model: Callable[..., torch.Tensor], scale: float
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) -> Callable[..., torch.Tensor]:
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def model_fn(x_t, ts, **kwargs):
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half = x_t[: len(x_t) // 2]
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combined = torch.cat([half, half], dim=0)
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model_out = model(combined, ts, **kwargs)
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eps, rest = model_out[:, :3], model_out[:, 3:]
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cond_eps, uncond_eps = torch.chunk(eps, 2, dim=0)
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half_eps = uncond_eps + scale * (cond_eps - uncond_eps)
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eps = torch.cat([half_eps, half_eps], dim=0)
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return torch.cat([eps, rest], dim=1)
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return model_fn
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def sample_latents(
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*,
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batch_size: int,
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model: nn.Module,
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diffusion: GaussianDiffusion,
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model_kwargs: Dict[str, Any],
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guidance_scale: float,
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clip_denoised: bool,
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use_fp16: bool,
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use_karras: bool,
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karras_steps: int,
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sigma_min: float,
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sigma_max: float,
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s_churn: float,
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device: Optional[torch.device] = None,
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progress: bool = False,
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) -> torch.Tensor:
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sample_shape = (batch_size, model.d_latent)
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if device is None:
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device = next(model.parameters()).device
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if hasattr(model, "cached_model_kwargs"):
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model_kwargs = model.cached_model_kwargs(batch_size, model_kwargs)
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if guidance_scale != 1.0 and guidance_scale != 0.0:
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for k, v in model_kwargs.copy().items():
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model_kwargs[k] = torch.cat([v, torch.zeros_like(v)], dim=0)
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sample_shape = (batch_size, model.d_latent)
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with torch.autocast(device_type=device.type, enabled=use_fp16):
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if use_karras:
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samples = karras_sample(
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diffusion=diffusion,
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model=model,
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shape=sample_shape,
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steps=karras_steps,
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clip_denoised=clip_denoised,
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model_kwargs=model_kwargs,
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device=device,
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sigma_min=sigma_min,
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sigma_max=sigma_max,
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s_churn=s_churn,
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guidance_scale=guidance_scale,
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progress=progress,
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)
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else:
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internal_batch_size = batch_size
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if guidance_scale != 1.0:
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model = uncond_guide_model(model, guidance_scale)
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internal_batch_size *= 2
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samples = diffusion.p_sample_loop(
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model,
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shape=(internal_batch_size, *sample_shape[1:]),
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model_kwargs=model_kwargs,
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device=device,
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clip_denoised=clip_denoised,
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progress=progress,
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)
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return samples
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