diff --git a/src/diffusers/schedulers/scheduling_unipc_multistep.py b/src/diffusers/schedulers/scheduling_unipc_multistep.py index fcc8fe2bef..1525845db3 100644 --- a/src/diffusers/schedulers/scheduling_unipc_multistep.py +++ b/src/diffusers/schedulers/scheduling_unipc_multistep.py @@ -278,6 +278,44 @@ class UniPCMultistepScheduler(SchedulerMixin, ConfigMixin): return sample + # Copied from diffusers.schedulers.scheduling_euler_discrete.EulerDiscreteScheduler._sigma_to_t + def _sigma_to_t(self, sigma, log_sigmas): + # get log sigma + log_sigma = np.log(sigma) + + # get distribution + dists = log_sigma - log_sigmas[:, np.newaxis] + + # get sigmas range + low_idx = np.cumsum((dists >= 0), axis=0).argmax(axis=0).clip(max=log_sigmas.shape[0] - 2) + high_idx = low_idx + 1 + + low = log_sigmas[low_idx] + high = log_sigmas[high_idx] + + # interpolate sigmas + w = (low - log_sigma) / (low - high) + w = np.clip(w, 0, 1) + + # transform interpolation to time range + t = (1 - w) * low_idx + w * high_idx + t = t.reshape(sigma.shape) + return t + + # Copied from diffusers.schedulers.scheduling_euler_discrete.EulerDiscreteScheduler._convert_to_karras + def _convert_to_karras(self, in_sigmas: torch.FloatTensor, num_inference_steps) -> torch.FloatTensor: + """Constructs the noise schedule of Karras et al. (2022).""" + + sigma_min: float = in_sigmas[-1].item() + sigma_max: float = in_sigmas[0].item() + + rho = 7.0 # 7.0 is the value used in the paper + ramp = np.linspace(0, 1, num_inference_steps) + min_inv_rho = sigma_min ** (1 / rho) + max_inv_rho = sigma_max ** (1 / rho) + sigmas = (max_inv_rho + ramp * (min_inv_rho - max_inv_rho)) ** rho + return sigmas + def convert_model_output( self, model_output: torch.FloatTensor, timestep: int, sample: torch.FloatTensor ) -> torch.FloatTensor: diff --git a/tests/schedulers/test_scheduler_unipc.py b/tests/schedulers/test_scheduler_unipc.py index 171ee85be1..0495f423e5 100644 --- a/tests/schedulers/test_scheduler_unipc.py +++ b/tests/schedulers/test_scheduler_unipc.py @@ -208,12 +208,24 @@ class UniPCMultistepSchedulerTest(SchedulerCommonTest): assert abs(result_mean.item() - 0.2464) < 1e-3 + def test_full_loop_with_karras(self): + sample = self.full_loop(use_karras_sigmas=True) + result_mean = torch.mean(torch.abs(sample)) + + assert abs(result_mean.item() - 0.2925) < 1e-3 + def test_full_loop_with_v_prediction(self): sample = self.full_loop(prediction_type="v_prediction") result_mean = torch.mean(torch.abs(sample)) assert abs(result_mean.item() - 0.1014) < 1e-3 + def test_full_loop_with_karras_and_v_prediction(self): + sample = self.full_loop(prediction_type="v_prediction", use_karras_sigmas=True) + result_mean = torch.mean(torch.abs(sample)) + + assert abs(result_mean.item() - 0.1966) < 1e-3 + def test_fp16_support(self): scheduler_class = self.scheduler_classes[0] scheduler_config = self.get_scheduler_config(thresholding=True, dynamic_thresholding_ratio=0)