|
| 1 | +import torch |
| 2 | + |
| 3 | +from .flow_matching import RectifiedFlowMatchingScheduler |
| 4 | + |
| 5 | + |
| 6 | +class DMDFlowMatchingScheduler(RectifiedFlowMatchingScheduler): |
| 7 | + def __init__(self, config, dmd_config={}): |
| 8 | + super().__init__(config) |
| 9 | + self.renoise_shift = float(dmd_config.get("renoise_shift", 5.0)) |
| 10 | + self.renoise_sigma_min = float(dmd_config.get("renoise_sigma_min", dmd_config.get("sigma_min", 0.02))) |
| 11 | + self.renoise_sigma_max = float(dmd_config.get("renoise_sigma_max", dmd_config.get("sigma_max", 1.0))) |
| 12 | + self.renoise_discrete_samples = int(dmd_config.get("renoise_discrete_samples", dmd_config.get("discrete_samples", 1000))) |
| 13 | + |
| 14 | + @staticmethod |
| 15 | + def linear_shift(mu, t): |
| 16 | + return mu / (mu + (1 / t - 1)) |
| 17 | + |
| 18 | + def set_timesteps(self, num_inference_steps, sigmas=None, latent_hw=None, device=None): |
| 19 | + super().set_timesteps(num_inference_steps, sigmas=sigmas, latent_hw=latent_hw) |
| 20 | + if device is not None: |
| 21 | + self.infer_sigmas = self.infer_sigmas.to(device) |
| 22 | + self.infer_timesteps = self.infer_timesteps.to(device) |
| 23 | + self.sigmas = self.infer_sigmas |
| 24 | + self.timesteps = self.infer_timesteps |
| 25 | + |
| 26 | + def sigma_at(self, step_idx, batch_size, device=None, dtype=None): |
| 27 | + sigma = self.sigmas[int(step_idx)].expand(int(batch_size)) |
| 28 | + if device is not None or dtype is not None: |
| 29 | + sigma = sigma.to(device=device, dtype=dtype) |
| 30 | + return sigma |
| 31 | + |
| 32 | + def sample_renoise_sigma(self, batch_size, device=None, dtype=None): |
| 33 | + device = device or self.device |
| 34 | + raw = torch.rand((int(batch_size),), device=device, dtype=torch.float32) |
| 35 | + if self.renoise_discrete_samples > 0: |
| 36 | + raw = torch.ceil(raw * self.renoise_discrete_samples) / self.renoise_discrete_samples |
| 37 | + raw = torch.clamp(raw, 1e-7, 1 - 1e-7) |
| 38 | + sigma = torch.clamp(self.linear_shift(self.renoise_shift, raw), self.renoise_sigma_min, self.renoise_sigma_max) |
| 39 | + if dtype is not None: |
| 40 | + sigma = sigma.to(dtype=dtype) |
| 41 | + return sigma |
| 42 | + |
| 43 | + def add_noise(self, latent, noise, sigmas): |
| 44 | + sigmas = sigmas.to(device=latent.device) |
| 45 | + sigmas = self._expand_to_ndim(sigmas, latent.ndim) |
| 46 | + return ((1.0 - sigmas) * latent + sigmas * noise).to(dtype=latent.dtype) |
| 47 | + |
| 48 | + def step_by_index(self, velocity, step_idx, sample): |
| 49 | + sigma = self.sigma_at(step_idx, sample.shape[0], device=sample.device) |
| 50 | + sigma_next = self.sigma_at(int(step_idx) + 1, sample.shape[0], device=sample.device) |
| 51 | + sigma = self._expand_to_ndim(sigma, sample.ndim) |
| 52 | + sigma_next = self._expand_to_ndim(sigma_next, sample.ndim) |
| 53 | + next_sample = sample + (sigma_next - sigma) * velocity |
| 54 | + x0 = sample - sigma * velocity |
| 55 | + return next_sample.to(sample.dtype), x0.to(sample.dtype) |
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