fix DPM Scheduler with `use_karras_sigmas` option (#6477)

* fix

---------
Co-authored-by: yiyixuxu <yixu310@gmail,com>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>

src/diffusers/schedulers/scheduling_dpmsolver_multistep.py

@@ -128,6 +128,9 @@ class DPMSolverMultistepScheduler(SchedulerMixin, ConfigMixin):
             Whether to use the uniform-logSNR for step sizes proposed by Lu's DPM-Solver in the noise schedule during
             the sampling process. If `True`, the sigmas and time steps are determined according to a sequence of
             `lambda(t)`.
+        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.
         lambda_min_clipped (`float`, defaults to `-inf`):
             Clipping threshold for the minimum value of `lambda(t)` for numerical stability. This is critical for the
             cosine (`squaredcos_cap_v2`) noise schedule.
@@ -165,11 +168,16 @@ class DPMSolverMultistepScheduler(SchedulerMixin, ConfigMixin):
         euler_at_final: bool = False,
         use_karras_sigmas: Optional[bool] = False,
         use_lu_lambdas: Optional[bool] = False,
+        final_sigmas_type: Optional[str] = "zero",  # "zero", "sigma_min"
         lambda_min_clipped: float = -float("inf"),
         variance_type: Optional[str] = None,
         timestep_spacing: str = "linspace",
         steps_offset: int = 0,
     ):
+        if algorithm_type in ["dpmsolver", "sde-dpmsolver"]:
+            deprecation_message = f"algorithm_type {algorithm_type} is deprecated and will be removed in a future version. Choose from `dpmsolver++` or `sde-dpmsolver++` instead"
+            deprecate("algorithm_types dpmsolver and sde-dpmsolver", "1.0.0", deprecation_message)
+
         if trained_betas is not None:
             self.betas = torch.tensor(trained_betas, dtype=torch.float32)
         elif beta_schedule == "linear":
@@ -207,6 +215,11 @@ class DPMSolverMultistepScheduler(SchedulerMixin, ConfigMixin):
             else:
                 raise NotImplementedError(f"{solver_type} does is not implemented for {self.__class__}")
 
+        if algorithm_type not in ["dpmsolver++", "sde-dpmsolver++"] and final_sigmas_type == "zero":
+            raise ValueError(
+                f"`final_sigmas_type` {final_sigmas_type} is not supported for `algorithm_type` {algorithm_type}. Please choose `sigma_min` instead."
+            )
+
         # setable values
         self.num_inference_steps = None
         timesteps = np.linspace(0, num_train_timesteps - 1, num_train_timesteps, dtype=np.float32)[::-1].copy()
@@ -267,16 +280,23 @@ class DPMSolverMultistepScheduler(SchedulerMixin, ConfigMixin):
             sigmas = np.flip(sigmas).copy()
             sigmas = self._convert_to_karras(in_sigmas=sigmas, num_inference_steps=num_inference_steps)
             timesteps = np.array([self._sigma_to_t(sigma, log_sigmas) for sigma in sigmas]).round()
-            sigmas = np.concatenate([sigmas, sigmas[-1:]]).astype(np.float32)
         elif self.config.use_lu_lambdas:
             lambdas = np.flip(log_sigmas.copy())
             lambdas = self._convert_to_lu(in_lambdas=lambdas, num_inference_steps=num_inference_steps)
             sigmas = np.exp(lambdas)
             timesteps = np.array([self._sigma_to_t(sigma, log_sigmas) for sigma in sigmas]).round()
-            sigmas = np.concatenate([sigmas, sigmas[-1:]]).astype(np.float32)
         else:
             sigmas = np.interp(timesteps, np.arange(0, len(sigmas)), sigmas)
+
+        if self.config.final_sigmas_type == "sigma_min":
             sigma_last = ((1 - self.alphas_cumprod[0]) / self.alphas_cumprod[0]) ** 0.5
+        elif self.config.final_sigmas_type == "zero":
+            sigma_last = 0
+        else:
+            raise ValueError(
+                f"`final_sigmas_type` must be one of 'zero', or 'sigma_min', but got {self.config.final_sigmas_type}"
+            )
+
         sigmas = np.concatenate([sigmas, [sigma_last]]).astype(np.float32)
 
         self.sigmas = torch.from_numpy(sigmas)
@@ -831,7 +851,9 @@ class DPMSolverMultistepScheduler(SchedulerMixin, ConfigMixin):
 
         # Improve numerical stability for small number of steps
         lower_order_final = (self.step_index == len(self.timesteps) - 1) and (
-            self.config.euler_at_final or (self.config.lower_order_final and len(self.timesteps) < 15)
+            self.config.euler_at_final
+            or (self.config.lower_order_final and len(self.timesteps) < 15)
+            or self.config.final_sigmas_type == "zero"
         )
         lower_order_second = (
             (self.step_index == len(self.timesteps) - 2) and self.config.lower_order_final and len(self.timesteps) < 15

src/diffusers/schedulers/scheduling_dpmsolver_multistep_inverse.py

@@ -165,6 +165,10 @@ class DPMSolverMultistepInverseScheduler(SchedulerMixin, ConfigMixin):
         timestep_spacing: str = "linspace",
         steps_offset: int = 0,
     ):
+        if algorithm_type in ["dpmsolver", "sde-dpmsolver"]:
+            deprecation_message = f"algorithm_type {algorithm_type} is deprecated and will be removed in a future version. Choose from `dpmsolver++` or `sde-dpmsolver++` instead"
+            deprecate("algorithm_types dpmsolver and sde-dpmsolver", "1.0.0", deprecation_message)
+
         if trained_betas is not None:
             self.betas = torch.tensor(trained_betas, dtype=torch.float32)
         elif beta_schedule == "linear":
@@ -783,7 +787,6 @@ class DPMSolverMultistepInverseScheduler(SchedulerMixin, ConfigMixin):
 
         self._step_index = step_index
 
-    # Copied from diffusers.schedulers.scheduling_dpmsolver_multistep.DPMSolverMultistepScheduler.step
     def step(
         self,
         model_output: torch.FloatTensor,

src/diffusers/schedulers/scheduling_dpmsolver_singlestep.py

@@ -108,7 +108,7 @@ class DPMSolverSinglestepScheduler(SchedulerMixin, ConfigMixin):
             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`, `dpmsolver++`, `sde-dpmsolver` or `sde-dpmsolver++`. The
+            Algorithm type for the solver; can be `dpmsolver` or `dpmsolver++`. The
             `dpmsolver` type implements the algorithms in the [DPMSolver](https://huggingface.co/papers/2206.00927)
             paper, and the `dpmsolver++` type implements the algorithms in the
             [DPMSolver++](https://huggingface.co/papers/2211.01095) paper. It is recommended to use `dpmsolver++` or
@@ -122,6 +122,9 @@ class DPMSolverSinglestepScheduler(SchedulerMixin, ConfigMixin):
         use_karras_sigmas (`bool`, *optional*, defaults to `False`):
             Whether to use Karras sigmas for step sizes in the noise schedule during the sampling process. If `True`,
             the sigmas are determined according to a sequence of noise levels {σi}.
+        final_sigmas_type (`str`, *optional*, 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.
         lambda_min_clipped (`float`, defaults to `-inf`):
             Clipping threshold for the minimum value of `lambda(t)` for numerical stability. This is critical for the
             cosine (`squaredcos_cap_v2`) noise schedule.
@@ -150,9 +153,14 @@ class DPMSolverSinglestepScheduler(SchedulerMixin, ConfigMixin):
         solver_type: str = "midpoint",
         lower_order_final: bool = True,
         use_karras_sigmas: Optional[bool] = False,
+        final_sigmas_type: Optional[str] = "zero",  # "zero", "sigma_min"
         lambda_min_clipped: float = -float("inf"),
         variance_type: Optional[str] = None,
     ):
+        if algorithm_type == "dpmsolver":
+            deprecation_message = "algorithm_type `dpmsolver` is deprecated and will be removed in a future version. Choose from `dpmsolver++` or `sde-dpmsolver++` instead"
+            deprecate("algorithm_types=dpmsolver", "1.0.0", deprecation_message)
+
         if trained_betas is not None:
             self.betas = torch.tensor(trained_betas, dtype=torch.float32)
         elif beta_schedule == "linear":
@@ -189,6 +197,11 @@ class DPMSolverSinglestepScheduler(SchedulerMixin, ConfigMixin):
             else:
                 raise NotImplementedError(f"{solver_type} does is not implemented for {self.__class__}")
 
+        if algorithm_type != "dpmsolver++" and final_sigmas_type == "zero":
+            raise ValueError(
+                f"`final_sigmas_type` {final_sigmas_type} is not supported for `algorithm_type` {algorithm_type}. Please chooose `sigma_min` instead."
+            )
+
         # setable values
         self.num_inference_steps = None
         timesteps = np.linspace(0, num_train_timesteps - 1, num_train_timesteps, dtype=np.float32)[::-1].copy()
@@ -267,10 +280,17 @@ class DPMSolverSinglestepScheduler(SchedulerMixin, ConfigMixin):
             sigmas = np.flip(sigmas).copy()
             sigmas = self._convert_to_karras(in_sigmas=sigmas, num_inference_steps=num_inference_steps)
             timesteps = np.array([self._sigma_to_t(sigma, log_sigmas) for sigma in sigmas]).round()
-            sigmas = np.concatenate([sigmas, sigmas[-1:]]).astype(np.float32)
         else:
             sigmas = np.interp(timesteps, np.arange(0, len(sigmas)), sigmas)
+
+        if self.config.final_sigmas_type == "sigma_min":
             sigma_last = ((1 - self.alphas_cumprod[0]) / self.alphas_cumprod[0]) ** 0.5
+        elif self.config.final_sigmas_type == "zero":
+            sigma_last = 0
+        else:
+            raise ValueError(
+                f" `final_sigmas_type` must be one of `sigma_min` or `zero`, but got {self.config.final_sigmas_type}"
+            )
         sigmas = np.concatenate([sigmas, [sigma_last]]).astype(np.float32)
 
         self.sigmas = torch.from_numpy(sigmas).to(device=device)
@@ -285,6 +305,12 @@ class DPMSolverSinglestepScheduler(SchedulerMixin, ConfigMixin):
             )
             self.register_to_config(lower_order_final=True)
 
+        if not self.config.lower_order_final and self.config.final_sigmas_type == "zero":
+            logger.warn(
+                " `last_sigmas_type='zero'` is not supported for `lower_order_final=False`. Changing scheduler {self.config} to have `lower_order_final` set to True."
+            )
+            self.register_to_config(lower_order_final=True)
+
         self.order_list = self.get_order_list(num_inference_steps)
 
         # add an index counter for schedulers that allow duplicated timesteps

tests/schedulers/test_scheduler_dpm_multi.py

@@ -32,6 +32,7 @@ class DPMSolverMultistepSchedulerTest(SchedulerCommonTest):
             "euler_at_final": False,
             "lambda_min_clipped": -float("inf"),
             "variance_type": None,
+            "final_sigmas_type": "sigma_min",
         }
 
         config.update(**kwargs)

tests/schedulers/test_scheduler_dpm_single.py

@@ -30,6 +30,7 @@ class DPMSolverSinglestepSchedulerTest(SchedulerCommonTest):
             "solver_type": "midpoint",
             "lambda_min_clipped": -float("inf"),
             "variance_type": None,
+            "final_sigmas_type": "sigma_min",
         }
 
         config.update(**kwargs)