Support for DDIMScheduler in Diffusion Policy (#146)

lerobot/common/policies/diffusion/configuration_diffusion.py

@@ -51,6 +51,7 @@ class DiffusionConfig:
         use_film_scale_modulation: FiLM (https://arxiv.org/abs/1709.07871) is used for the Unet conditioning.
             Bias modulation is used be default, while this parameter indicates whether to also use scale
             modulation.
+        noise_scheduler_type: Name of the noise scheduler to use. Supported options: ["DDPM", "DDIM"].
         num_train_timesteps: Number of diffusion steps for the forward diffusion schedule.
         beta_schedule: Name of the diffusion beta schedule as per DDPMScheduler from Hugging Face diffusers.
         beta_start: Beta value for the first forward-diffusion step.
@@ -110,6 +111,7 @@ class DiffusionConfig:
     diffusion_step_embed_dim: int = 128
     use_film_scale_modulation: bool = True
     # Noise scheduler.
+    noise_scheduler_type: str = "DDPM"
     num_train_timesteps: int = 100
     beta_schedule: str = "squaredcos_cap_v2"
     beta_start: float = 0.0001
@@ -144,3 +146,9 @@ class DiffusionConfig:
             raise ValueError(
                 f"`prediction_type` must be one of {supported_prediction_types}. Got {self.prediction_type}."
             )
+        supported_noise_schedulers = ["DDPM", "DDIM"]
+        if self.noise_scheduler_type not in supported_noise_schedulers:
+            raise ValueError(
+                f"`noise_scheduler_type` must be one of {supported_noise_schedulers}. "
+                f"Got {self.noise_scheduler_type}."
+            )

lerobot/common/policies/diffusion/modeling_diffusion.py

@@ -13,6 +13,7 @@ import einops
 import torch
 import torch.nn.functional as F  # noqa: N812
 import torchvision
+from diffusers.schedulers.scheduling_ddim import DDIMScheduler
 from diffusers.schedulers.scheduling_ddpm import DDPMScheduler
 from huggingface_hub import PyTorchModelHubMixin
 from robomimic.models.base_nets import SpatialSoftmax
@@ -126,6 +127,19 @@ class DiffusionPolicy(nn.Module, PyTorchModelHubMixin):
         return {"loss": loss}
 
 
+def _make_noise_scheduler(name: str, **kwargs: dict) -> DDPMScheduler | DDIMScheduler:
+    """
+    Factory for noise scheduler instances of the requested type. All kwargs are passed
+    to the scheduler.
+    """
+    if name == "DDPM":
+        return DDPMScheduler(**kwargs)
+    elif name == "DDIM":
+        return DDIMScheduler(**kwargs)
+    else:
+        raise ValueError(f"Unsupported noise scheduler type {name}")
+
+
 class DiffusionModel(nn.Module):
     def __init__(self, config: DiffusionConfig):
         super().__init__()
@@ -138,12 +152,12 @@ class DiffusionModel(nn.Module):
             * config.n_obs_steps,
         )
 
-        self.noise_scheduler = DDPMScheduler(
+        self.noise_scheduler = _make_noise_scheduler(
+            config.noise_scheduler_type,
             num_train_timesteps=config.num_train_timesteps,
             beta_start=config.beta_start,
             beta_end=config.beta_end,
             beta_schedule=config.beta_schedule,
-            variance_type="fixed_small",
             clip_sample=config.clip_sample,
             clip_sample_range=config.clip_sample_range,
             prediction_type=config.prediction_type,

lerobot/configs/policy/diffusion.yaml

@@ -85,6 +85,7 @@ policy:
   diffusion_step_embed_dim: 128
   use_film_scale_modulation: True
   # Noise scheduler.
+  noise_scheduler_type: DDPM
   num_train_timesteps: 100
   beta_schedule: squaredcos_cap_v2
   beta_start: 0.0001