add step_index and clear noise_sampler at begining of each loop (#5024)

Co-authored-by: yiyixuxu <yixu310@gmail,com>

src/diffusers/schedulers/scheduling_dpmsolver_sde.py

@@ -199,6 +199,7 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
         self.use_karras_sigmas = use_karras_sigmas
         self.noise_sampler = None
         self.noise_sampler_seed = noise_sampler_seed
+        self._step_index = None
 
     # Copied from diffusers.schedulers.scheduling_heun_discrete.HeunDiscreteScheduler.index_for_timestep
     def index_for_timestep(self, timestep, schedule_timesteps=None):
@@ -219,6 +220,24 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
 
         return indices[pos].item()
 
+    # Copied from diffusers.schedulers.scheduling_euler_discrete.EulerDiscreteScheduler._init_step_index
+    def _init_step_index(self, timestep):
+        if isinstance(timestep, torch.Tensor):
+            timestep = timestep.to(self.timesteps.device)
+
+        index_candidates = (self.timesteps == timestep).nonzero()
+
+        # The sigma index that is taken for the **very** first `step`
+        # is always the second index (or the last index if there is only 1)
+        # This way we can ensure we don't accidentally skip a sigma in
+        # case we start in the middle of the denoising schedule (e.g. for image-to-image)
+        if len(index_candidates) > 1:
+            step_index = index_candidates[1]
+        else:
+            step_index = index_candidates[0]
+
+        self._step_index = step_index.item()
+
     @property
     def init_noise_sigma(self):
         # standard deviation of the initial noise distribution
@@ -227,6 +246,13 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
 
         return (self.sigmas.max() ** 2 + 1) ** 0.5
 
+    @property
+    def step_index(self):
+        """
+        The index counter for current timestep. It will increae 1 after each scheduler step.
+        """
+        return self._step_index
+
     def scale_model_input(
         self,
         sample: torch.FloatTensor,
@@ -246,9 +272,10 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
             `torch.FloatTensor`:
                 A scaled input sample.
         """
-        step_index = self.index_for_timestep(timestep)
+        if self.step_index is None:
+            self._init_step_index(timestep)
 
-        sigma = self.sigmas[step_index]
+        sigma = self.sigmas[self.step_index]
         sigma_input = sigma if self.state_in_first_order else self.mid_point_sigma
         sample = sample / ((sigma_input**2 + 1) ** 0.5)
         return sample
@@ -321,6 +348,9 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
         self.sample = None
         self.mid_point_sigma = None
 
+        self._step_index = None
+        self.noise_sampler = None
+
         # for exp beta schedules, such as the one for `pipeline_shap_e.py`
         # we need an index counter
         self._index_counter = defaultdict(int)
@@ -411,7 +441,8 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
                 If return_dict is `True`, [`~schedulers.scheduling_utils.SchedulerOutput`] is returned, otherwise a
                 tuple is returned where the first element is the sample tensor.
         """
-        step_index = self.index_for_timestep(timestep)
+        if self.step_index is None:
+            self._init_step_index(timestep)
 
         # advance index counter by 1
         timestep_int = timestep.cpu().item() if torch.is_tensor(timestep) else timestep
@@ -430,12 +461,12 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
             return _sigma.log().neg()
 
         if self.state_in_first_order:
-            sigma = self.sigmas[step_index]
-            sigma_next = self.sigmas[step_index + 1]
+            sigma = self.sigmas[self.step_index]
+            sigma_next = self.sigmas[self.step_index + 1]
         else:
             # 2nd order
-            sigma = self.sigmas[step_index - 1]
-            sigma_next = self.sigmas[step_index]
+            sigma = self.sigmas[self.step_index - 1]
+            sigma_next = self.sigmas[self.step_index]
 
         # Set the midpoint and step size for the current step
         midpoint_ratio = 0.5
@@ -488,6 +519,9 @@ class DPMSolverSDEScheduler(SchedulerMixin, ConfigMixin):
                 self.sample = None
                 self.mid_point_sigma = None
 
+        # upon completion increase step index by one
+        self._step_index += 1
+
         if not return_dict:
             return (prev_sample,)