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chore: import upstream snapshot with attribution
2026-07-13 12:29:08 +08:00

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Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""
Benchmark quantization quality loss for diffusion models (image & video).
Generates outputs with BF16 (baseline) and a quantized config using the same
seed, then computes LPIPS perceptual distance between them. Results are printed
as a Markdown table ready to paste into a PR description.
Requirements:
pip install lpips Pillow numpy
Image example (text-to-image):
python benchmarks/diffusion/quantization_quality.py \
--model Tongyi-MAI/Z-Image-Turbo \
--task t2i \
--quantization fp8 \
--prompts \
"an aerial view of a coral reef with crystal clear turquoise water" \
"a campfire in a dark forest with sparks rising into a starry sky" \
"a gourmet dessert plate with chocolate mousse and gold leaf" \
--height 1024 --width 1024 \
--num-inference-steps 50 --seed 42
Video example (text-to-video):
python benchmarks/diffusion/quantization_quality.py \
--model Wan-AI/Wan2.2-T2V-A14B-Diffusers \
--task t2v \
--quantization fp8 \
--prompts \
"A serene lakeside sunrise with mist over the water" \
"A cat walking across a wooden bridge in autumn" \
--height 720 --width 1280 \
--num-frames 81 --num-inference-steps 40 --seed 42
LTX-2 example (text-to-video; audio output is generated but not scored by LPIPS):
python benchmarks/diffusion/quantization_quality.py \
--model Lightricks/LTX-Video-2 \
--task t2v \
--quantization fp8 int8 \
--prompts \
"A serene lakeside sunrise with mist over the water" \
--height 704 --width 1216 \
--num-frames 121 --num-inference-steps 40 --seed 42
Multiple quantization methods:
python benchmarks/diffusion/quantization_quality.py \
--model Tongyi-MAI/Z-Image-Turbo \
--task t2i \
--quantization fp8 int8 bitsandbytes \
--prompts "a cup of coffee on the table" \
--height 1024 --width 1024 \
--num-inference-steps 50 --seed 42
Output directory structure (--output-dir, default: ./quant_bench_output):
quant_bench_output/
baseline/ # BF16 outputs
<method>/ # Quantized outputs per method
results.md # Markdown table
"""
import argparse
import gc
import time
from pathlib import Path
import numpy as np
import torch
def compute_lpips_images(
baseline_images: list,
quantized_images: list,
net: str = "alex",
) -> list[float]:
"""Compute LPIPS between paired lists of PIL images."""
import lpips
from torchvision import transforms
loss_fn = lpips.LPIPS(net=net).eval()
if torch.cuda.is_available():
loss_fn = loss_fn.cuda()
transform = transforms.Compose(
[
transforms.Resize((256, 256)),
transforms.ToTensor(),
transforms.Normalize(mean=[0.5, 0.5, 0.5], std=[0.5, 0.5, 0.5]),
]
)
scores = []
for img_bl, img_qt in zip(baseline_images, quantized_images):
t_bl = transform(img_bl.convert("RGB")).unsqueeze(0)
t_qt = transform(img_qt.convert("RGB")).unsqueeze(0)
if torch.cuda.is_available():
t_bl, t_qt = t_bl.cuda(), t_qt.cuda()
with torch.no_grad():
score = loss_fn(t_bl, t_qt).item()
scores.append(score)
return scores
def compute_lpips_video(
baseline_frames: np.ndarray,
quantized_frames: np.ndarray,
net: str = "alex",
) -> float:
"""Compute mean per-frame LPIPS for a video pair.
Args:
baseline_frames: (F, H, W, C) float array in [0, 1].
quantized_frames: same shape.
Returns:
Mean LPIPS across all frames.
"""
import lpips
loss_fn = lpips.LPIPS(net=net).eval()
if torch.cuda.is_available():
loss_fn = loss_fn.cuda()
num_frames = min(len(baseline_frames), len(quantized_frames))
scores = []
for i in range(num_frames):
# Convert (H, W, C) float [0,1] -> (1, C, H, W) float [-1, 1]
f_bl = torch.from_numpy(baseline_frames[i]).permute(2, 0, 1).unsqueeze(0).float() * 2 - 1
f_qt = torch.from_numpy(quantized_frames[i]).permute(2, 0, 1).unsqueeze(0).float() * 2 - 1
if torch.cuda.is_available():
f_bl, f_qt = f_bl.cuda(), f_qt.cuda()
with torch.no_grad():
score = loss_fn(f_bl, f_qt).item()
scores.append(score)
return float(np.mean(scores))
def _build_omni_kwargs(args, quantization=None):
"""Build kwargs dict for Omni() constructor."""
from vllm_omni.diffusion.data import DiffusionParallelConfig
parallel_config = DiffusionParallelConfig(
ulysses_degree=args.ulysses_degree,
ring_degree=args.ring_degree,
tensor_parallel_size=args.tensor_parallel_size,
)
kwargs = {
"model": args.model,
"parallel_config": parallel_config,
"enforce_eager": args.enforce_eager,
}
if quantization:
kwargs["quantization_config"] = quantization
return kwargs
def _generate_image(omni, args, prompt, seed):
"""Generate a single image and return (PIL.Image, time_seconds, memory_gib)."""
from vllm_omni.inputs.data import OmniDiffusionSamplingParams
from vllm_omni.outputs import OmniRequestOutput
from vllm_omni.platforms import current_omni_platform
generator = torch.Generator(device=current_omni_platform.device_type).manual_seed(seed)
torch.accelerator.reset_peak_memory_stats()
start = time.perf_counter()
outputs = omni.generate(
{"prompt": prompt},
OmniDiffusionSamplingParams(
height=args.height,
width=args.width,
generator=generator,
num_inference_steps=args.num_inference_steps,
),
)
elapsed = time.perf_counter() - start
peak_mem = torch.accelerator.max_memory_allocated() / (1024**3)
req_out = OmniRequestOutput.unwrap_result(outputs)
if not req_out.images:
raise ValueError("Could not extract image output from result.")
img = req_out.images[0]
return img, elapsed, peak_mem
def _generate_video(omni, args, prompt, seed):
"""Generate a video and return (np.ndarray [F,H,W,C], time_seconds, memory_gib)."""
from vllm_omni.inputs.data import OmniDiffusionSamplingParams
from vllm_omni.outputs import OmniRequestOutput
from vllm_omni.platforms import current_omni_platform
generator = torch.Generator(device=current_omni_platform.device_type).manual_seed(seed)
torch.accelerator.reset_peak_memory_stats()
start = time.perf_counter()
outputs = omni.generate(
{"prompt": prompt, "negative_prompt": ""},
OmniDiffusionSamplingParams(
height=args.height,
width=args.width,
generator=generator,
guidance_scale=args.guidance_scale,
num_inference_steps=args.num_inference_steps,
num_frames=args.num_frames,
),
)
elapsed = time.perf_counter() - start
peak_mem = torch.accelerator.max_memory_allocated() / (1024**3)
first = outputs[0]
if hasattr(first, "request_output") and isinstance(first.request_output, list):
inner = first.request_output[0]
if isinstance(inner, OmniRequestOutput) and hasattr(inner, "images"):
frames = inner.images[0] if inner.images else None
else:
frames = inner
elif hasattr(first, "images") and first.images:
frames = first.images[0]
else:
raise ValueError("Could not extract video frames from output.")
# LTX-2 (and similar audio+video models) may surface a dict or (video, audio) tuple
if isinstance(frames, dict):
frames = frames.get("video") or frames.get("frames")
elif isinstance(frames, tuple) and len(frames) == 2:
frames = frames[0]
if frames is None:
raise ValueError("Could not extract video frames from output.")
if isinstance(frames, torch.Tensor):
video = frames.detach().cpu()
if video.dim() == 5:
video = video[0].permute(1, 2, 3, 0) if video.shape[1] in (3, 4) else video[0]
elif video.dim() == 4 and video.shape[0] in (3, 4):
video = video.permute(1, 2, 3, 0)
if video.is_floating_point():
video = video.clamp(-1, 1) * 0.5 + 0.5
frames_array = video.float().numpy()
else:
frames_array = np.asarray(frames)
if frames_array.ndim == 5:
frames_array = frames_array[0]
return frames_array, elapsed, peak_mem
def _free_gpu_memory():
"""Force GC and release cached GPU memory.
Must be called AFTER the caller has dropped (i.e., via `del`)
every reference to the Omni instance"""
gc.collect()
if torch.cuda.is_available():
torch.accelerator.empty_cache()
torch.accelerator.synchronize()
def run_benchmark(args):
from vllm_omni.entrypoints.omni import Omni
output_dir = Path(args.output_dir)
output_dir.mkdir(parents=True, exist_ok=True)
is_video = args.task == "t2v"
prompts = args.prompts
seed = args.seed
# Determine configs to benchmark
configs = [] # list of (label, quantization_method)
for method in args.quantization:
configs.append((method, method))
# --- Baseline run ---
print("\n" + "=" * 60)
print("Running BF16 baseline...")
print("=" * 60)
bl_kwargs = _build_omni_kwargs(args, quantization=None)
omni_bl = Omni(**bl_kwargs)
baseline_outputs = {} # prompt -> (output, time, mem)
for prompt in prompts:
print(f" Generating: {prompt[:60]}...")
if is_video:
out, t, mem = _generate_video(omni_bl, args, prompt, seed)
else:
out, t, mem = _generate_image(omni_bl, args, prompt, seed)
baseline_outputs[prompt] = (out, t, mem)
bl_avg_time = np.mean([v[1] for v in baseline_outputs.values()])
bl_mem = baseline_outputs[prompts[0]][2] # use first prompt's memory
omni_bl.shutdown()
del omni_bl
_free_gpu_memory()
# Save baseline outputs
bl_dir = output_dir / "baseline"
bl_dir.mkdir(parents=True, exist_ok=True)
for i, prompt in enumerate(prompts):
out = baseline_outputs[prompt][0]
if is_video:
try:
from diffusers.utils import export_to_video
frames_list = list(out) if isinstance(out, np.ndarray) and out.ndim == 4 else out
export_to_video(frames_list, str(bl_dir / f"prompt_{i}.mp4"), fps=args.fps)
except ImportError:
np.save(bl_dir / f"prompt_{i}.npy", out)
else:
out.save(bl_dir / f"prompt_{i}.png")
# --- Quantized runs ---
all_results = [] # list of dicts
for config_label, quant_method in configs:
print(f"\n{'=' * 60}")
print(f"Running: {config_label}...")
print("=" * 60)
qt_kwargs = _build_omni_kwargs(args, quantization=quant_method)
omni_qt = Omni(**qt_kwargs)
qt_outputs = {}
for prompt in prompts:
print(f" Generating: {prompt[:60]}...")
if is_video:
out, t, mem = _generate_video(omni_qt, args, prompt, seed)
else:
out, t, mem = _generate_image(omni_qt, args, prompt, seed)
qt_outputs[prompt] = (out, t, mem)
qt_avg_time = np.mean([v[1] for v in qt_outputs.values()])
qt_mem = qt_outputs[prompts[0]][2]
omni_qt.shutdown()
del omni_qt
_free_gpu_memory()
# Save quantized outputs
qt_dir = output_dir / config_label.replace(" ", "_")
qt_dir.mkdir(parents=True, exist_ok=True)
# Compute LPIPS per prompt
per_prompt = []
for i, prompt in enumerate(prompts):
bl_out = baseline_outputs[prompt][0]
qt_out = qt_outputs[prompt][0]
if is_video:
lpips_score = compute_lpips_video(bl_out, qt_out, net=args.lpips_net)
try:
from diffusers.utils import export_to_video
frames_list = list(qt_out) if isinstance(qt_out, np.ndarray) and qt_out.ndim == 4 else qt_out
export_to_video(frames_list, str(qt_dir / f"prompt_{i}.mp4"), fps=args.fps)
except ImportError:
np.save(qt_dir / f"prompt_{i}.npy", qt_out)
else:
lpips_score = compute_lpips_images([bl_out], [qt_out], net=args.lpips_net)[0]
qt_out.save(qt_dir / f"prompt_{i}.png")
per_prompt.append({"prompt": prompt, "lpips": lpips_score})
mean_lpips = np.mean([p["lpips"] for p in per_prompt])
speedup = bl_avg_time / qt_avg_time if qt_avg_time > 0 else float("inf")
mem_reduction = (bl_mem - qt_mem) / bl_mem * 100
all_results.append(
{
"config": config_label,
"avg_time": qt_avg_time,
"speedup": speedup,
"memory_gib": qt_mem,
"mem_reduction_pct": mem_reduction,
"mean_lpips": mean_lpips,
"per_prompt": per_prompt,
}
)
# --- Print results ---
print("\n\n")
print("=" * 80)
print("RESULTS")
print("=" * 80)
# Summary table
lines = []
lines.append(f"## Quantization Quality Benchmark — {args.model.split('/')[-1]}")
lines.append(
f"Setup: {args.height}x{args.width}, {args.num_inference_steps} steps, "
f"seed={args.seed}, LPIPS ({args.lpips_net})"
)
if is_video:
lines.append(f"Video: {args.num_frames} frames")
lines.append("")
lines.append("### Summary")
lines.append("")
lines.append("| Config | Avg Time | Speedup | Memory (GiB) | Mem Reduction | Mean LPIPS |")
lines.append("|--------|----------|---------|--------------|---------------|------------|")
lines.append(f"| BF16 baseline | {bl_avg_time:.2f}s | 1.00x | {bl_mem:.2f} | — | (ref) |")
for r in all_results:
lines.append(
f"| {r['config']} | {r['avg_time']:.2f}s | {r['speedup']:.2f}x "
f"| {r['memory_gib']:.2f} | {r['mem_reduction_pct']:.0f}% "
f"| {r['mean_lpips']:.4f} |"
)
lines.append("")
lines.append("> LPIPS < 0.01 = imperceptible, > 0.1 = clearly noticeable.")
lines.append("")
# Per-prompt table
if len(prompts) > 1:
lines.append("### Per-Prompt LPIPS")
lines.append("")
header = "| Prompt |"
sep = "|--------|"
for r in all_results:
header += f" {r['config']} |"
sep += "--------|"
lines.append(header)
lines.append(sep)
for i, prompt in enumerate(prompts):
short = prompt[:50] + "..." if len(prompt) > 50 else prompt
row = f"| {short} |"
for r in all_results:
row += f" {r['per_prompt'][i]['lpips']:.4f} |"
lines.append(row)
lines.append("")
md = "\n".join(lines)
print(md)
# Save markdown
results_path = output_dir / "results.md"
results_path.write_text(md, encoding="utf-8")
print(f"\nResults saved to {results_path}")
print(f"Baseline outputs in {bl_dir}")
for r in all_results:
qt_dir = output_dir / r["config"].replace(" ", "_")
print(f"Quantized outputs in {qt_dir}")
def parse_args():
parser = argparse.ArgumentParser(
description="Benchmark quantization quality loss for diffusion models.",
formatter_class=argparse.RawDescriptionHelpFormatter,
)
parser.add_argument("--model", required=True, help="Model name or local path.")
parser.add_argument(
"--task",
default="t2i",
choices=["t2i", "t2v"],
help="Task type: t2i (text-to-image) or t2v (text-to-video).",
)
parser.add_argument(
"--quantization",
nargs="+",
required=True,
help="One or more quantization methods to benchmark (e.g. fp8 int8 bitsandbytes).",
)
parser.add_argument(
"--prompts",
nargs="+",
default=["a cup of coffee on the table"],
help="One or more prompts to generate.",
)
parser.add_argument("--seed", type=int, default=42)
parser.add_argument("--height", type=int, default=1024)
parser.add_argument("--width", type=int, default=1024)
parser.add_argument("--num-inference-steps", type=int, default=50)
parser.add_argument("--num-frames", type=int, default=81, help="Number of video frames (t2v only).")
parser.add_argument("--fps", type=int, default=24, help="Video FPS for saving (t2v only).")
parser.add_argument("--guidance-scale", type=float, default=4.0, help="CFG scale (used for video).")
parser.add_argument("--output-dir", type=str, default="./quant_bench_output", help="Directory to save outputs.")
parser.add_argument(
"--lpips-net",
type=str,
default="alex",
choices=["alex", "vgg", "squeeze"],
help="LPIPS backbone network.",
)
parser.add_argument("--ulysses-degree", type=int, default=1)
parser.add_argument("--ring-degree", type=int, default=1)
parser.add_argument("--tensor-parallel-size", type=int, default=1)
parser.add_argument("--enforce-eager", action="store_true")
return parser.parse_args()
if __name__ == "__main__":
args = parse_args()
run_benchmark(args)