add rebuild() to Scheduler interface

for use in `set_inference_steps()`

src/refiners/foundationals/latent_diffusion/model.py

@@ -33,15 +33,7 @@ class LatentDiffusionModel(fl.Module, ABC):
         self.scheduler = scheduler.to(device=self.device, dtype=self.dtype)
 
     def set_inference_steps(self, num_steps: int, first_step: int = 0) -> None:
-        initial_diffusion_rate = self.scheduler.initial_diffusion_rate
-        final_diffusion_rate = self.scheduler.final_diffusion_rate
-        device, dtype = self.scheduler.device, self.scheduler.dtype
-        self.scheduler = self.scheduler.__class__(
-            num_inference_steps=num_steps,
-            initial_diffusion_rate=initial_diffusion_rate,
-            final_diffusion_rate=final_diffusion_rate,
-            first_inference_step=first_step,
-        ).to(device=device, dtype=dtype)
+        self.scheduler = self.scheduler.rebuild(num_inference_steps=num_steps, first_inference_step=first_step)
 
     def init_latents(
         self,

src/refiners/foundationals/latent_diffusion/schedulers/dpm_solver.py

@@ -51,6 +51,18 @@ class DPMSolver(Scheduler):
             device=self.device,
         ).flip(0)
 
+    def rebuild(
+        self: "DPMSolver",
+        num_inference_steps: int | None,
+        first_inference_step: int | None = None,
+    ) -> "DPMSolver":
+        r = super().rebuild(
+            num_inference_steps=num_inference_steps,
+            first_inference_step=first_inference_step,
+        )
+        r.last_step_first_order = self.last_step_first_order
+        return r
+
     def dpm_solver_first_order_update(self, x: Tensor, noise: Tensor, step: int) -> Tensor:
         current_timestep = self.timesteps[step]
         previous_timestep = self.timesteps[step + 1] if step < self.num_inference_steps - 1 else tensor([0])

src/refiners/foundationals/latent_diffusion/schedulers/scheduler.py

@@ -77,6 +77,20 @@ class Scheduler(ABC):
     def inference_steps(self) -> list[int]:
         return self.all_steps[self.first_inference_step :]
 
+    def rebuild(self: T, num_inference_steps: int | None, first_inference_step: int | None = None) -> T:
+        num_inference_steps = self.num_inference_steps if num_inference_steps is None else num_inference_steps
+        first_inference_step = self.first_inference_step if first_inference_step is None else first_inference_step
+        return self.__class__(
+            num_inference_steps=num_inference_steps,
+            num_train_timesteps=self.num_train_timesteps,
+            initial_diffusion_rate=self.initial_diffusion_rate,
+            final_diffusion_rate=self.final_diffusion_rate,
+            noise_schedule=self.noise_schedule,
+            first_inference_step=first_inference_step,
+            device=self.device,
+            dtype=self.dtype,
+        )
+
     def scale_model_input(self, x: Tensor, step: int) -> Tensor:
         """
         For compatibility with schedulers that need to scale the input according to the current timestep.