(Phase 1)Add ModelOpt FP8 auto-detect support for diffusion checkpoints #2709 (#2913)

Signed-off-by: roG0d <rodgarcas98@gmail.com>
Signed-off-by: roG0d <baonudesifeizhai@gmail.com>
Signed-off-by: baonudesifeizhai <85092850+baonudesifeizhai@users.noreply.github.com>
Co-authored-by: roG0d <rodgarcas98@gmail.com>
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## Overview
FP8 quantization converts BF16/FP16 weights to FP8 at model load time, or loads
a checkpoint whose target stage already declares an FP8 quantization config.
Online activation scaling is the default and does not require calibration.
Static activation scaling is supported when calibrated scale information is
available.
FP8 quantization converts BF16/FP16 weights to FP8 at model load time. Online
activation scaling is the default and does not require calibration. Static
activation scaling is supported when calibrated scale information is available.
For ModelOpt-produced pre-quantized checkpoints, see
[ModelOpt Quantization](modelopt.md).
Some architectures can quantize all linear layers. Others have
quality-sensitive layers that should stay in BF16 through `ignored_layers`.
@@ -46,7 +46,7 @@ guide. FP8 on Ampere may use a weight-only path where available.
| Model | Scope | Format | Status |
|-------|-------|--------|--------|
| Qwen3-Omni | Thinker language-model stage | ModelOpt `quant_algo=FP8` | Tested for thinker memory reduction |
| Qwen3-Omni | Thinker language-model stage | [ModelOpt](modelopt.md) `quant_algo=FP8` | Tested for thinker memory reduction |
| Qwen3-TTS | TTS language-model stage | Checkpoint config | Not validated |
Audio encoder, vision encoder, talker, and code2wav stay in BF16 unless a
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# ModelOpt Quantization
## Overview
ModelOpt quantization loads checkpoints produced by NVIDIA ModelOpt. The
quantized weights and scale tensors are generated before serving, so inference
does not run online calibration or convert a BF16 checkpoint at startup.
vLLM-Omni currently validates the ModelOpt FP8 checkpoint path for diffusion
transformers. The loader auto-detects supported ModelOpt FP8 checkpoint configs
and keeps non-transformer components, such as the tokenizer, scheduler, text
encoder, and VAE, on the base checkpoint unless a model-specific guide says
otherwise.
!!! note
`--force-cutlass-fp8` is an explicit runtime override for diffusion
checkpoints that already carry a supported ModelOpt FP8 config. It does not
quantize BF16 checkpoints and it does not apply to online `--quantization
fp8`. The flag only takes effect for ModelOpt FP8 diffusion stages on CUDA
SM89+ devices; other platforms and non-ModelOpt FP8 paths fall back to the
normal vLLM kernel selection.
## Supported ModelOpt Checkpoint Formats
vLLM-Omni treats ModelOpt checkpoints as pre-quantized checkpoints. The
checkpoint config must identify ModelOpt as the quantization method or producer,
and the quantization algorithm must be one of the validated FP8 algorithms.
| Checkpoint field | Supported value |
|------------------|-----------------|
| `method` / `quant_method` | `modelopt` |
| `producer.name` | `modelopt` |
| `quant_algo` | `FP8`, `FP8_PER_CHANNEL_PER_TOKEN` |
Other ModelOpt algorithms, such as NVFP4, are not enabled by this diffusion
FP8 path until they have separate model and quality validation.
## Hardware Support
| Device | Support |
|--------|---------|
| NVIDIA Blackwell GPU (SM 100+) | ✅ |
| NVIDIA Ada/Hopper GPU (SM 89+) | ✅ |
| NVIDIA Ampere GPU (SM 80+) | ⭕ |
| AMD ROCm | ⭕ |
| Intel XPU | ⭕ |
| Ascend NPU | ❌ |
Legend: `✅` supported, `❌` unsupported, `⭕` not verified in this guide.
The optional CUTLASS FP8 runtime override requires CUDA SM89+.
## Model Type Support
### Diffusion Model
| Model | HF checkpoint | Scope | Status |
|-------|---------------|-------|--------|
| Qwen-Image 2512 | `feizhai123/qwen-image-2512-modelopt-fp8-dynamic-all` | Diffusion transformer | Validated for ModelOpt FP8 checkpoints |
| Z-Image | `feizhai123/z-image-modelopt-fp8-conservative` | Diffusion transformer | Validated for ModelOpt FP8 checkpoints |
| FLUX.2-dev | `feizhai123/flux2-dev-modelopt-fp8` | Diffusion transformer | Validated for ModelOpt FP8 checkpoints |
| FLUX.2-klein 4B | `feizhai123/flux2-klein-4b-modelopt-fp8` | Diffusion transformer | Validated for ModelOpt FP8 checkpoints |
| HunyuanImage-3.0 | `feizhai123/hunyuan-image3-modelopt-fp8` | MoE diffusion transformer | Validated for ModelOpt FP8 checkpoints |
| Wan2.2 | Not available | Diffusion transformer | Not validated |
### Multi-Stage Omni/TTS Model
| Model | Scope | Status |
|-------|-------|--------|
| Qwen3-Omni | Thinker language-model stage | ModelOpt FP8 checkpoint path |
| Qwen3-TTS | TTS language-model stage | Not validated |
Audio encoder, vision encoder, talker, and code2wav stages stay in BF16 unless
a model-specific guide documents otherwise.
### Multi-Stage Diffusion Model
ModelOpt checkpoints must be routed to the stage whose checkpoint contains the
ModelOpt `quantization_config`. BAGEL and GLM-Image are not listed as validated
ModelOpt targets yet.
## Configuration
For pre-quantized ModelOpt FP8 checkpoints, no `--quantization fp8` flag is
needed. The checkpoint config selects the ModelOpt path.
Online serving:
```bash
vllm serve <modelopt-fp8-checkpoint> \
--omni \
--tensor-parallel-size <N> \
--force-cutlass-fp8
```
Offline inference:
```bash
python examples/offline_inference/text_to_image/text_to_image.py \
--model <modelopt-fp8-checkpoint> \
--tensor-parallel-size <N> \
--prompt "a red ceramic teapot on a wooden table" \
--height 1024 \
--width 1024 \
--num-inference-steps 20 \
--seed 42 \
--output outputs/modelopt_fp8.png
```
Python API:
```python
from vllm_omni import Omni
omni = Omni(
model="<modelopt-fp8-checkpoint>",
tensor_parallel_size=2,
force_cutlass_fp8=True,
)
```
## Parameters
| Parameter | Type | Default | Description |
|-----------|------|---------|-------------|
| `force_cutlass_fp8` / `--force-cutlass-fp8` | bool | `False` | Force CUTLASS FP8 linear kernels for supported ModelOpt FP8 diffusion stages on CUDA SM89+ |
## Validation and Notes
1. Compare the ModelOpt FP8 checkpoint against the BF16 baseline with the same
prompt, resolution, seed, and inference steps.
2. Use `tests/diffusion/quantization/test_quantization_quality.py` with
`VLLM_OMNI_QUALITY_CONFIGS` to validate local baseline and quantized model
paths.
3. Report LPIPS, PSNR, MAE, throughput, latency, and peak memory when adding a
new validated ModelOpt diffusion checkpoint.
4. Keep `--quantization fp8` for online FP8 from BF16 checkpoints; use this
ModelOpt path only when the checkpoint already contains ModelOpt FP8 weights
and scales.
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| Mode | Guide | Description | Methods |
|------|-------|-------------|---------|
| Online quantization | [Online Quantization](online.md) | vLLM-Omni computes quantized weights and scales while loading the model. | FP8 W8A8, Int8 W8A8 |
| Pre-quantized checkpoints | Method-specific guides | The checkpoint or an offline quantizer provides quantized weights and scales before serving. | GGUF, AutoRound, msModelSlim, serialized Int8 |
| Pre-quantized checkpoints | Method-specific guides | The checkpoint or an offline quantizer provides quantized weights and scales before serving. | ModelOpt, GGUF, AutoRound, msModelSlim, serialized Int8 |
## Hardware Support
| Device | FP8 W8A8 | Int8 W8A8 | GGUF | AutoRound | msModelSlim |
|--------|----------|-----------|------|-----------|-------------|
| NVIDIA Blackwell GPU (SM 100+) | ✅ | ✅ | ✅ | ✅ | ❌ |
| NVIDIA Ada/Hopper GPU (SM 89+) | ✅ | ✅ | ✅ | ✅ | ❌ |
| NVIDIA Ampere GPU (SM 80+) | ✅ | ✅ | ✅ | ✅ | ❌ |
| AMD ROCm | ⭕ | ⭕ | ⭕ | ⭕ | ❌ |
| Intel XPU | ⭕ | ⭕ | ⭕ | ✅ | ❌ |
| Ascend NPU | ❌ | ✅ | ❌ | ❌ | ✅ |
| Device | FP8 W8A8 | Int8 W8A8 | ModelOpt | GGUF | AutoRound | msModelSlim |
|--------|----------|-----------|----------|------|-----------|-------------|
| NVIDIA Blackwell GPU (SM 100+) | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ |
| NVIDIA Ada/Hopper GPU (SM 89+) | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ |
| NVIDIA Ampere GPU (SM 80+) | ✅ | ✅ | ⭕ | ✅ | ✅ | ❌ |
| AMD ROCm | ⭕ | ⭕ | ⭕ | ⭕ | ⭕ | ❌ |
| Intel XPU | ⭕ | ⭕ | ⭕ | ⭕ | ✅ | ❌ |
| Ascend NPU | ❌ | ✅ | ❌ | ❌ | ❌ | ✅ |
Legend: `✅` supported, `❌` unsupported, `⭕` not verified in this
guide. FP8 on Ampere may use a weight-only path where available.
@@ -39,6 +39,7 @@ otherwise.
|--------|-------|------|----------------|--------|
| FP8 W8A8 | [FP8](fp8.md) | Online W8A8 or checkpoint FP8 | Qwen-Image; Wan2.2 is not validated | Validated for Qwen-Image family and other DiT models |
| Int8 W8A8 | [Int8](int8.md) | Online or serialized W8A8 | Qwen-Image; Wan2.2 is not validated | Validated for Qwen-Image and Z-Image |
| ModelOpt | [ModelOpt](modelopt.md) | Pre-quantized FP8 checkpoints | Qwen-Image, Z-Image, FLUX.2, HunyuanImage-3.0 | Validated for ModelOpt FP8 diffusion checkpoints |
| GGUF | [GGUF](gguf.md) | Pre-quantized transformer weights | Qwen-Image | Validated where a model-specific GGUF adapter exists |
| AutoRound | [AutoRound](autoround.md) | Pre-quantized W4A16 checkpoints | FLUX.1-dev; Qwen-Image/Wan2.2 not validated | Checkpoint-driven |
| msModelSlim | [msModelSlim](msmodelslim.md) | Pre-quantized Ascend checkpoints | Wan2.2 recipe; HunyuanImage-3.0 inference target | Ascend/NPU path |
@@ -52,7 +53,7 @@ in BF16 unless the model guide explicitly adds support.
| Method | Guide | Scope | Example models | Status |
|--------|-------|-------|----------------|--------|
| FP8 | [FP8](fp8.md) | Thinker or language-model checkpoint config | Qwen3-Omni thinker | ModelOpt checkpoint path |
| ModelOpt | [ModelOpt](modelopt.md) | Thinker or language-model checkpoint config | Qwen3-Omni thinker | ModelOpt checkpoint path |
| Int8 | [Int8](int8.md) | Not currently validated for omni/TTS stages | Qwen3-Omni, Qwen3-TTS | Not validated |
| GGUF | [GGUF](gguf.md) | Not currently validated for omni/TTS stages | Qwen3-Omni, Qwen3-TTS | Not validated |
| AutoRound | [AutoRound](autoround.md) | Thinker or language-model checkpoint config | Qwen2.5-Omni, Qwen3-Omni | Supported through AutoRound checkpoints |
@@ -67,6 +68,7 @@ attached to the intended stage rather than applied globally.
|--------|-------|-------|----------------|--------|
| FP8 | [FP8](fp8.md) | Stage-specific DiT or transformer module | BAGEL, GLM-Image | Requires model-specific validation |
| Int8 | [Int8](int8.md) | Stage-specific DiT or transformer module | BAGEL, GLM-Image | Requires model-specific validation |
| ModelOpt | [ModelOpt](modelopt.md) | Checkpoint-defined diffusion stage | BAGEL, GLM-Image | Requires model-specific validation |
| GGUF | [GGUF](gguf.md) | Stage-specific transformer weights | BAGEL, GLM-Image | No validated adapter listed |
| AutoRound | [AutoRound](autoround.md) | Checkpoint-defined stage | BAGEL, GLM-Image | No validated checkpoint listed |
| msModelSlim | [msModelSlim](msmodelslim.md) | Ascend-generated stage weights | GLM-Image | Requires model-specific adaptation |
@@ -94,7 +96,7 @@ config = build_quant_config({
| Component | Default quantized? | Notes |
|-----------|--------------------|-------|
| Diffusion transformer | Yes | Primary target for FP8, Int8, GGUF, AutoRound, and msModelSlim |
| Diffusion transformer | Yes | Primary target for FP8, Int8, ModelOpt, GGUF, AutoRound, and msModelSlim |
| Text encoder | No | Keep BF16 unless a method-specific guide documents support |
| VAE | No | Keep BF16; storage-only paths are method-specific |
| Scheduler/tokenizer | No | Loaded from the base model repository |