[None][feat] Enable FA4 + parallel VAE in LTX-2 examples - #17610
[None][feat] Enable FA4 + parallel VAE in LTX-2 examples#17610luyiyun1021 wants to merge 2 commits into
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Bring the LTX-2 example configs in line with the latest VisualGen optimizations, matching how the Wan and Cosmos examples already ship them. - ltx2-4gpu.yaml: switch attention backend VANILLA -> FA4 and add parallel_vae_size: 4 (async_ulysses was already enabled). It was the only multi-GPU VG config missing VAE parallelism. - ltx2-t2v-fp4-1gpu.yaml / ltx2-t2v-fp8-1gpu.yaml: switch attention backend VANILLA -> FA4. Also fix two stale doc references to non-existent config files: - README: configs/ltx2-t2v-fp8-1-gpu.yaml -> ltx2-t2v-fp8-1gpu.yaml. - models/ltx2.py docstring: ../configs/ltx2.yaml -> ../configs/ltx2-t2v-fp8-1gpu.yaml. Signed-off-by: Yiyun Lu <55233584+luyiyun1021@users.noreply.github.com>
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WalkthroughLTX-2 examples now use FA4 attention and include a shared 1-GPU configuration. The model example accepts auxiliary paths for two-stage inference, and documentation and integration tests use updated configuration names. ChangesLTX-2 example configuration updates
Estimated code review effort: 2 (Simple) | ~10 minutes Mergeability Score: ⚪ Minimal · up to This change only updates example configurations and documentation; no actionable merge-blocking risk remains after normal checks and review. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Add a bf16 (unquantized) 1-GPU LTX-2 example config as the default single-GPU config (ltx2-1gpu.yaml) and point the README and ltx2.py usage at it. Drop the redundant t2v qualifier from the LTX-2 config names (LTX-2 does not use separate t2v/i2v configs): ltx2-t2v-{fp4,fp8}-1gpu.yaml -> ltx2-{fp4,fp8}-1gpu.yaml, updating the integration-test reference. Also expose --spatial_upsampler_path / --distilled_lora_path on the ltx2.py example runner so two-stage inference (distilled-LoRA + spatial upsampler) can be forced on checkpoints that do not bundle the auxiliary files. The full Lightricks/LTX-2 checkpoint already auto-enables two-stage via checkpoint-dir discovery; the flags cover stripped checkpoints without baking non-portable paths into the shipped configs.
Signed-off-by: Yiyun Lu <55233584+luyiyun1021@users.noreply.github.com>
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In `@tests/integration/defs/examples/visual_gen/test_visual_gen_ltx2.py`:
- Line 433: Add test_ltx2_example to the appropriate manual-QA test list under
tests/integration/test_lists/qa/, preserving its existing CI registration in
l0_b200.yml and marking the GPU, model-weight, and LLM_MODELS_ROOT requirements
according to the surrounding QA entries.
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📒 Files selected for processing (6)
examples/visual_gen/README.mdexamples/visual_gen/configs/ltx2-1gpu.yamlexamples/visual_gen/configs/ltx2-fp4-1gpu.yamlexamples/visual_gen/configs/ltx2-fp8-1gpu.yamlexamples/visual_gen/models/ltx2.pytests/integration/defs/examples/visual_gen/test_visual_gen_ltx2.py
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- examples/visual_gen/models/ltx2.py
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Description
Bring the LTX-2 examples in line with the latest VisualGen optimizations, matching how the Wan and Cosmos examples already ship them. Before this change no LTX-2 config in the repo used FA4 attention or parallel VAE, and
ltx2-4gpu.yamlwas the only multi-GPU VisualGen config missingparallel_vae_size. This PR enables FA4 attention across the LTX-2 example configs and adds VAE parallelism to the 4-GPU config (async_ulysseswas already enabled). It also fixes two stale references to a non-existentltx2.yaml.Changes:
configs/ltx2-4gpu.yaml: attention backendVANILLA→FA4, addparallel_vae_size: 4.configs/ltx2-t2v-fp4-1gpu.yaml/configs/ltx2-t2v-fp8-1gpu.yaml: attention backendVANILLA→FA4.README.md: fixconfigs/ltx2-t2v-fp8-1-gpu.yaml→configs/ltx2-t2v-fp8-1gpu.yaml.models/ltx2.pydocstring:../configs/ltx2.yaml→../configs/ltx2-t2v-fp8-1gpu.yaml.Test Coverage
Example-config and documentation change only; no source or runtime code paths are modified. Each config remains a valid
VisualGenArgspayload (FA4 is a supported backend Literal;parallel_vae_size: 4equals the 4-GPU world size). The FA4 + async-Ulysses combination on the 4-GPU path is a pure-Ulysses all-to-all composition that wraps any inner backend, and the FA4 backend already runs standalone in the 1-GPU configs. Runtime validation is via the LTX-2 perf-sanity / CI runs.PR Checklist
Please review the following before submitting your PR:
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PR Follows TRT-LLM CODING GUIDELINES to the best of your knowledge.
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If PR introduces API changes, an appropriate PR label is added - either
api-compatibleorapi-breaking. Forapi-breaking, includeBREAKINGin the PR title.Any new dependencies have been scanned for license and vulnerabilities
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Please check this after reviewing the above items as appropriate for this PR.
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/bot help.Dev Engineer Review
FA4attention in the LTX-2 4-GPU, FP4 1-GPU, and FP8 1-GPU configurations.ltx2-1gpu.yamlfor shared offline visual-generation andtrtllm-serveuse.parallel_vae_size: 4to the 4-GPU configuration.README.md,models/ltx2.py, and the integration test.models/ltx2.py.QA Engineer Review
tests/integration/defs/examples/visual_gen/test_visual_gen_ltx2.py.ltx2-fp4-1gpu.yaml.