62 lines
1.9 KiB
Markdown
62 lines
1.9 KiB
Markdown
# Step Execution
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Step execution is an opt-in diffusion execution mode enabled with
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`step_execution=True` when constructing `Omni`.
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It is not a generic diffusion toggle for every pipeline. Only pipelines that
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implement the stepwise contract support it today.
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## Quick Start
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```python
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from vllm_omni import Omni
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from vllm_omni.inputs.data import OmniDiffusionSamplingParams
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omni = Omni(
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model="Qwen/Qwen-Image",
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step_execution=True,
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)
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outputs = omni.generate(
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"A cat sitting on a windowsill",
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OmniDiffusionSamplingParams(
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num_inference_steps=50,
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),
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)
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```
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## Supported Pipelines
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| Pipeline | Example models | Step execution |
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|----------|----------------|----------------|
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| `QwenImagePipeline` | `Qwen/Qwen-Image`, `Qwen/Qwen-Image-2512` | Yes |
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| All other diffusion pipelines | `QwenImageEditPipeline`, `QwenImageEditPlusPipeline`, `QwenImageLayeredPipeline`, GLM-Image, Wan, Flux, etc. | No |
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## Current Limitations
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- `step_execution` currently supports `batch_size=1` only.
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- `cache_backend` is not supported together with step execution.
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- Unsupported pipelines fail early during model loading.
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- Request-mode extras such as KV transfer are not wired into step mode yet.
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## When To Use It
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Use step execution only when you specifically need the pipeline to run through
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its stepwise request state machine. For normal diffusion inference, leave it
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disabled unless your workflow depends on this mode.
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If you are looking for general diffusion speedups, see
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[Diffusion Acceleration Overview](../diffusion_acceleration.md).
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## Troubleshooting
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If model loading fails with a message mentioning `prepare_encode()`,
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`denoise_step()`, `step_scheduler()`, and `post_decode()`, the selected
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pipeline does not support step execution.
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## For Model Authors
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If you want to add step execution support to a new diffusion pipeline, see the
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implementation guide:
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[Diffusion Step Execution Design](../../design/feature/diffusion_step_execution.md).
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