Hotfix to make second order schedulers work with mask (#4378)

## What type of PR is this? (check all applicable)

- [ ] Refactor
- [ ] Feature
- [x] Bug Fix
- [ ] Optimization
- [ ] Documentation Update
- [ ] Community Node Submission


## Have you discussed this change with the InvokeAI team?
- [x] Yes
- [ ] No, because:

      
## Have you updated all relevant documentation?
- [ ] Yes
- [ ] No


## Description


## Related Tickets & Documents


## QA Instructions, Screenshots, Recordings


## Added/updated tests?

- [ ] Yes
- [ ] No : _please replace this line with details on why tests
      have not been included_

invokeai/app/invocations/latent.py

@@ -367,36 +367,31 @@ def prep_control_data(
     # original idea by https://github.com/AmericanPresidentJimmyCarter
     # TODO: research more for second order schedulers timesteps
     def init_scheduler(self, scheduler, device, steps, denoising_start, denoising_end):
-        num_inference_steps = steps
         if scheduler.config.get("cpu_only", False):
-            scheduler.set_timesteps(num_inference_steps, device="cpu")
+            scheduler.set_timesteps(steps, device="cpu")
             timesteps = scheduler.timesteps.to(device=device)
         else:
-            scheduler.set_timesteps(num_inference_steps, device=device)
+            scheduler.set_timesteps(steps, device=device)
             timesteps = scheduler.timesteps
 
-        # apply denoising_start
-        t_start_val = int(round(scheduler.config.num_train_timesteps * (1 - denoising_start)))
-        t_start_idx = len(list(filter(lambda ts: ts >= t_start_val, timesteps)))
-        timesteps = timesteps[t_start_idx:]
-        if scheduler.order == 2 and t_start_idx > 0:
-            timesteps = timesteps[1:]
+        # skip greater order timesteps
+        _timesteps = timesteps[:: scheduler.order]
 
-        # save start timestep to apply noise
-        init_timestep = timesteps[:1]
+        # get start timestep index
+        t_start_val = int(round(scheduler.config.num_train_timesteps * (1 - denoising_start)))
+        t_start_idx = len(list(filter(lambda ts: ts >= t_start_val, _timesteps)))
 
-        # apply denoising_end
+        # get end timestep index
         t_end_val = int(round(scheduler.config.num_train_timesteps * (1 - denoising_end)))
-        t_end_idx = len(list(filter(lambda ts: ts >= t_end_val, timesteps)))
-        if scheduler.order == 2 and t_end_idx > 0:
-            t_end_idx += 1
-        timesteps = timesteps[:t_end_idx]
-
-        # calculate step count based on scheduler order
-        num_inference_steps = len(timesteps)
-        if scheduler.order == 2:
-            num_inference_steps += num_inference_steps % 2
-            num_inference_steps = num_inference_steps // 2
+        t_end_idx = len(list(filter(lambda ts: ts >= t_end_val, _timesteps[t_start_idx:])))
+
+        # apply order to indexes
+        t_start_idx *= scheduler.order
+        t_end_idx *= scheduler.order
+
+        init_timestep = timesteps[t_start_idx : t_start_idx + 1]
+        timesteps = timesteps[t_start_idx : t_start_idx + t_end_idx]
+        num_inference_steps = len(timesteps) // scheduler.order
 
         return num_inference_steps, timesteps, init_timestep
 

invokeai/backend/stable_diffusion/diffusers_pipeline.py

@@ -558,12 +558,22 @@ def step(
         # compute the previous noisy sample x_t -> x_t-1
         step_output = self.scheduler.step(noise_pred, timestep, latents, **conditioning_data.scheduler_args)
 
+        # TODO: issue to diffusers?
+        # undo internal counter increment done by scheduler.step, so timestep can be resolved as before call
+        # this needed to be able call scheduler.add_noise with current timestep
+        if self.scheduler.order == 2:
+            self.scheduler._index_counter[timestep.item()] -= 1
+
         # TODO: this additional_guidance extension point feels redundant with InvokeAIDiffusionComponent.
         #    But the way things are now, scheduler runs _after_ that, so there was
         #    no way to use it to apply an operation that happens after the last scheduler.step.
         for guidance in additional_guidance:
             step_output = guidance(step_output, timestep, conditioning_data)
 
+        # restore internal counter
+        if self.scheduler.order == 2:
+            self.scheduler._index_counter[timestep.item()] += 1
+
         return step_output
 
     def _unet_forward(