Set scheduler begin index in remaining FlowMatch pipelines to avoid DtoH sync - #14576
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…toH sync Propagate the set_begin_index(0) fix from huggingface#11696 to HunyuanVideo, Mochi, Lumina2, AuraFlow, and Chroma text-to-image/video pipelines. Without it, the first scheduler.step() routes through _init_step_index() -> index_for_timestep(), whose nonzero().item() forces a device-to-host sync on the first denoising step. Fixes huggingface#14573.
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What does this PR do?
Fixes #14573.
#11696 added
self.scheduler.set_begin_index(0)before the denoising loop inFluxPipelineto avoid the device-to-host sync fromnonzero().item()inFlowMatchEulerDiscreteScheduler.index_for_timestep(). That fix was later propagated to Wan, QwenImage, and others, but fiveFlowMatchEulerDiscreteSchedulerpipelines never received it: HunyuanVideo, Mochi, Lumina2, AuraFlow, and Chroma (text-to-image).This PR applies the identical one-line pattern (with the same comment pointing at #11696) to those five. SD3 is intentionally excluded since open PR #14176 already covers it.
Verified on CPU with the repo's dummy-component fixtures: before, each pipeline enters
index_for_timestep(the.item()sync path) once on the first step; after, zero entries,begin_index == 0, outputs unchanged. Fast test suites for all five pipelines show no new failures versus main;make style/check_copiesclean. Like #11696, no new tests, since the eliminated sync is only observable in a profiler trace.Before submitting
Who can review?
@yiyixuxu @dg845