IndexError on num_inference_steps values: 3, 9, 27, ...?

Describe the bug

Some num_inference_steps values seem to be “problematic” and throw an IndexError.

Also the iteration status output does not end on that value in any relation. If it’s on purpose, it’s still confusing:

num_inference_steps: 5 6it [00:49, 8.27s/it]

num_inference_steps: 6 8it [01:02, 7.87s/it]

num_inference_steps: 7 9it [01:10, 7.88s/it]

num_inference_steps: 8 9it [01:13, 8.19s/it]

Reproduction

from diffusers import StableDiffusionPipeline

TOKEN = "(censored)"
MODEL_ID = "CompVis/stable-diffusion-v1-4"

pipe = StableDiffusionPipeline.from_pretrained(MODEL_ID, use_auth_token=TOKEN)
res = pipe("a photo of an astronaut riding a horse on mars", num_inference_steps=3, guidance_scale=7.5)

Tested on command line too. Unrelated to PyCharm environment.

Logs

/usr/bin/python3 /home/as/.config/JetBrains/PyCharm2022.2/scratches/scratch.py 

0it [00:07, ?it/s]
Traceback (most recent call last):
  File "/home/as/.config/JetBrains/PyCharm2022.2/scratches/scratch.py", line 7, in <module>
    res = pipe("a photo of an astronaut riding a horse on mars", num_inference_steps=3, guidance_scale=7.5)
  File "/home/as/.local/lib/python3.10/site-packages/torch/autograd/grad_mode.py", line 27, in decorate_context
    return func(*args, **kwargs)
  File "/usr/lib/python3.10/site-packages/diffusers/pipelines/stable_diffusion/pipeline_stable_diffusion.py", line 148, in __call__
    latents = self.scheduler.step(noise_pred, t, latents, **extra_step_kwargs)["prev_sample"]
  File "/usr/lib/python3.10/site-packages/diffusers/schedulers/scheduling_pndm.py", line 136, in step
    return self.step_plms(model_output=model_output, timestep=timestep, sample=sample)
  File "/usr/lib/python3.10/site-packages/diffusers/schedulers/scheduling_pndm.py", line 212, in step_plms
    prev_sample = self._get_prev_sample(sample, timestep, prev_timestep, model_output)
  File "/usr/lib/python3.10/site-packages/diffusers/schedulers/scheduling_pndm.py", line 230, in _get_prev_sample
    alpha_prod_t = self.alphas_cumprod[timestep + 1 - self._offset]
IndexError: index 1000 is out of bounds for dimension 0 with size 1000

System Info

• diffusers version: 0.4.0.dev0
• Platform: Linux-5.19.7-arch1-1-x86_64-with-glibc2.36
• Python version: 3.10.6
• PyTorch version (GPU?): 1.12.1+cu102 (True)
• Huggingface_hub version: 0.9.1
• Transformers version: 4.21.3
• Using GPU in script?: No
• Using distributed or parallel set-up in script?: No

[sausix]

@natolambert Thank for fixing quickly. Will test it tommorrow too. Found some other non 3 related iterations yesterday.

[natolambert]

I opened #465 to keep this on track about the indexing error / confusion.