diffusers/pr_13966/en/api/schedulers/edm_multistep_dpm_solver.md

EDMDPMSolverMultistepScheduler

EDMDPMSolverMultistepScheduler is a Karras formulation of DPMSolverMultistepScheduler, a multistep scheduler from DPM-Solver: A Fast ODE Solver for Diffusion Probabilistic Model Sampling in Around 10 Steps and DPM-Solver++: Fast Solver for Guided Sampling of Diffusion Probabilistic Models by Cheng Lu, Yuhao Zhou, Fan Bao, Jianfei Chen, Chongxuan Li, and Jun Zhu.

DPMSolver (and the improved version DPMSolver++) is a fast dedicated high-order solver for diffusion ODEs with convergence order guarantee. Empirically, DPMSolver sampling with only 20 steps can generate high-quality samples, and it can generate quite good samples even in 10 steps.

EDMDPMSolverMultistepScheduler[[diffusers.EDMDPMSolverMultistepScheduler]]

• sigma_min (float, optional, defaults to 0.002) -- Minimum noise magnitude in the sigma schedule. This was set to 0.002 in the EDM paper [1]; a reasonable range is [0, 10].
• sigma_max (float, optional, defaults to 80.0) -- Maximum noise magnitude in the sigma schedule. This was set to 80.0 in the EDM paper [1]; a reasonable range is [0.2, 80.0].
• sigma_data (float, optional, defaults to 0.5) -- The standard deviation of the data distribution. This is set to 0.5 in the EDM paper [1].
• sigma_schedule (str, optional, defaults to karras) -- Sigma schedule to compute the sigmas. By default, we the schedule introduced in the EDM paper (https://huggingface.co/papers/2206.00364). Other acceptable value is "exponential". The exponential schedule was incorporated in this model: https://huggingface.co/stabilityai/cosxl.
• num_train_timesteps (int, defaults to 1000) -- The number of diffusion steps to train the model.
• prediction_type (str, defaults to epsilon, optional) -- Prediction type of the scheduler function; can be epsilon (predicts the noise of the diffusion process), sample (directly predicts the noisy sample) or v_prediction` (see section 2.4 of Imagen Video paper).
• rho (float, optional, defaults to 7.0) -- The rho parameter in the Karras sigma schedule. This was set to 7.0 in the EDM paper [1].
• solver_order (int, defaults to 2) -- The DPMSolver order which can be 1 or 2 or 3. It is recommended to use solver_order=2 for guided sampling, and solver_order=3 for unconditional sampling.
• thresholding (bool, defaults to False) -- Whether to use the "dynamic thresholding" method. This is unsuitable for latent-space diffusion models such as Stable Diffusion.
• dynamic_thresholding_ratio (float, defaults to 0.995) -- The ratio for the dynamic thresholding method. Valid only when thresholding=True.
• sample_max_value (float, defaults to 1.0) -- The threshold value for dynamic thresholding. Valid only when thresholding=True and algorithm_type="dpmsolver++".
• algorithm_type (str, defaults to dpmsolver++) -- Algorithm type for the solver; can be dpmsolver++ or sde-dpmsolver++. The dpmsolver++ type implements the algorithms in the DPMSolver++ paper. It is recommended to use dpmsolver++ or sde-dpmsolver++ with solver_order=2 for guided sampling like in Stable Diffusion.
• solver_type (str, defaults to midpoint) -- Solver type for the second-order solver; can be midpoint or heun. The solver type slightly affects the sample quality, especially for a small number of steps. It is recommended to use midpoint solvers.
• lower_order_final (bool, defaults to True) -- Whether to use lower-order solvers in the final steps. Only valid for < 15 inference steps. This can stabilize the sampling of DPMSolver for steps < 15, especially for steps <= 10.
• euler_at_final (bool, defaults to False) -- Whether to use Euler's method in the final step. It is a trade-off between numerical stability and detail richness. This can stabilize the sampling of the SDE variant of DPMSolver for small number of inference steps, but sometimes may result in blurring.
• final_sigmas_type (str, defaults to "zero") -- The final sigma value for the noise schedule during the sampling process. If "sigma_min", the final sigma is the same as the last sigma in the training schedule. If zero, the final sigma is set to 0.

Implements DPMSolverMultistepScheduler in EDM formulation as presented in Karras et al. 2022 [1]. EDMDPMSolverMultistepScheduler is a fast dedicated high-order solver for diffusion ODEs.

[1] Karras, Tero, et al. "Elucidating the Design Space of Diffusion-Based Generative Models." https://huggingface.co/papers/2206.00364

This model inherits from SchedulerMixin and ConfigMixin. Check the superclass documentation for the generic methods the library implements for all schedulers such as loading and saving.

• original_samples (torch.Tensor) -- The original samples to which noise will be added.
• noise (torch.Tensor) -- The noise tensor to add to the original samples.
• timesteps (torch.Tensor) -- The timesteps at which to add noise, determining the noise level from the schedule.torch.TensorThe noisy samples with added noise scaled according to the timestep schedule.

Add noise to the original samples according to the noise schedule at the specified timesteps.

• model_output (torch.Tensor) -- The direct output from the learned diffusion model.
• sample (torch.Tensor) -- A current instance of a sample created by the diffusion process.torch.TensorThe converted model output.

Convert the model output to the corresponding type the DPMSolver/DPMSolver++ algorithm needs. DPM-Solver is designed to discretize an integral of the noise prediction model, and DPM-Solver++ is designed to discretize an integral of the data prediction model.

> The algorithm and model type are decoupled. You can use either DPMSolver or DPMSolver++ for both noise > prediction and data prediction models.

• model_output (torch.Tensor) -- The direct output from the learned diffusion model.
• sample (torch.Tensor) -- A current instance of a sample created by the diffusion process.
• noise (torch.Tensor, optional) -- The noise tensor to add to the original samples.torch.TensorThe sample tensor at the previous timestep.

One step for the first-order DPMSolver (equivalent to DDIM).

• timestep (int or torch.Tensor) -- The timestep for which to find the index.
• schedule_timesteps (torch.Tensor, optional) -- The timestep schedule to search in. If None, uses self.timesteps.intThe index of the timestep in the schedule.

Find the index for a given timestep in the schedule.

• model_output_list (list[torch.Tensor]) -- The direct outputs from learned diffusion model at current and latter timesteps.
• sample (torch.Tensor) -- A current instance of a sample created by the diffusion process.
• noise (torch.Tensor, optional) -- The noise tensor to add to the original samples.torch.TensorThe sample tensor at the previous timestep.

One step for the second-order multistep DPMSolver.

• model_output_list (list[torch.Tensor]) -- The direct outputs from learned diffusion model at current and latter timesteps.
• sample (torch.Tensor) -- A current instance of a sample created by diffusion process.torch.TensorThe sample tensor at the previous timestep.

One step for the third-order multistep DPMSolver.

• sample (torch.Tensor) -- The input sample tensor to precondition.
• sigma (float or torch.Tensor) -- The current sigma (noise level) value.torch.TensorThe scaled input sample.

Precondition the input sample by scaling it according to the EDM formulation.

• sigma (float or torch.Tensor) -- The sigma (noise level) value to precondition.torch.TensorThe preconditioned noise value computed as 0.25 * log(sigma).

Precondition the noise level by applying a logarithmic transformation.

• sample (torch.Tensor) -- The input sample tensor.
• model_output (torch.Tensor) -- The direct output from the learned diffusion model.
• sigma (float or torch.Tensor) -- The current sigma (noise level) value.torch.TensorThe denoised sample computed by combining the skip connection and output scaling.

Precondition the model outputs according to the EDM formulation.

• sample (torch.Tensor) -- The input sample tensor.
• timestep (float or torch.Tensor) -- The current timestep in the diffusion chain.torch.TensorA scaled input sample.

Scale the denoising model input to match the Euler algorithm. Ensures interchangeability with schedulers that need to scale the denoising model input depending on the current timestep.

• begin_index (int, defaults to 0) -- The begin index for the scheduler.

Sets the begin index for the scheduler. This function should be run from pipeline before the inference.

• num_inference_steps (int) -- The number of diffusion steps used when generating samples with a pre-trained model.
• device (str or torch.device, optional) -- The device to which the timesteps should be moved to. If None, the timesteps are not moved.

Sets the discrete timesteps used for the diffusion chain (to be run before inference).

• model_output (torch.Tensor) -- The direct output from learned diffusion model.
• timestep (int) -- The current discrete timestep in the diffusion chain.
• sample (torch.Tensor) -- A current instance of a sample created by the diffusion process.
• generator (torch.Generator, optional) -- A random number generator.
• return_dict (bool) -- Whether or not to return a SchedulerOutput or tuple.SchedulerOutput or tupleIf return_dict is True, SchedulerOutput is returned, otherwise a tuple is returned where the first element is the sample tensor.

Predict the sample from the previous timestep by reversing the SDE. This function propagates the sample with the multistep DPMSolver.

SchedulerOutput[[diffusers.schedulers.scheduling_utils.SchedulerOutput]]

• prev_sample (torch.Tensor of shape (batch_size, num_channels, height, width) for images) -- Computed sample (x_{t-1}) of previous timestep. prev_sample should be used as next model input in the denoising loop.

Base class for the output of a scheduler's step function.