Fix num_images_per_prompt>1 with Skip Guidance Layers in StableDiffusion3Pipeline

[hlky]

What does this PR do?

#10085 (comment) for some further details.

Fixes #10085

Who can review?

Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

cc @sayakpaul @japppie

[hlky]

Note there is some small visual difference between num_images_per_prompt=1 and num_images_per_prompt=2:

num_images_per_prompt=1

num_images_per_prompt=2

This also occurs without skip_guidance_layers:

num_images_per_prompt=1

num_images_per_prompt=2

[HuggingFaceDocBuilderDev]

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[yiyixuxu]

thanks a lot for the fix! @hlky
so the implementation was wrong before and just happen to got broadcasted inside one of the AdaLayerNorm

[yiyixuxu]

can we add more tests here

diffusers/tests/pipelines/stable_diffusion_3/test_pipeline_stable_diffusion_3.py

Line 123 in cd34439

def test_stable_diffusion_3_different_prompts(self):

to test num_images_per_prompt =2 for SLG with and without CFG

[yiyixuxu]

feel free to merge once tested is add (or you can add test in a separate PR!)

[hlky]

Yes it's easily missed, important to check batch support for new models etc. going forward.

Looks like tests for num_images_per_prompt are missing from some other pipelines like Flux as well so I'll add them all in another PR.

[sayakpaul]

Looks like tests for num_images_per_prompt are missing from some other pipelines like Flux as well so I'll add them all in another PR.

@hlky

I think it would make sense to introduce/revisit the pipeline tester mixin to see how we can make it more general so that this is tested by default without us having to write it for every pipeline/model test suite. WDYT?

Feel free to ping me and @DN6 if you need further ideas here.