[Diffusion] Non-Intrusive Sequence Parallelism (SP) Model Support Abstraction for vLLM-Omni Framework (#779)

Signed-off-by: mxuax <mxuax@connect.ust.hk>
Signed-off-by: XU Mingshi <91017482+mxuax@users.noreply.github.com>
This commit is contained in:
XU Mingshi authored and GitHub committed 2026-01-21 14:43:09 +08:00
1 parent 334d306d9a
commit 25b08b3371
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@@ -9,6 +9,7 @@ correctly with diffusion models. It uses minimal settings to keep test time
short for CI.
"""
import gc
import os
import sys
import time
@@ -21,7 +22,7 @@ import torch.distributed as dist
from PIL import Image
# ruff: noqa: E402
REPO_ROOT = Path(__file__).resolve().parents[2]
REPO_ROOT = Path(__file__).resolve().parents[3]
if str(REPO_ROOT) not in sys.path:
sys.path.insert(0, str(REPO_ROOT))
@@ -30,7 +31,6 @@ from vllm_omni.diffusion.data import DiffusionParallelConfig
from vllm_omni.diffusion.distributed.parallel_state import device_count
from vllm_omni.diffusion.envs import get_device_name
# Use random weights model for testing
models = ["riverclouds/qwen_image_random"]
PROMPT = "a photo of a cat sitting on a laptop keyboard"
@@ -51,44 +51,145 @@ def _diff_metrics(a: Image.Image, b: Image.Image) -> tuple[float, float]:
return abs_diff.mean().item(), abs_diff.max().item()
def _get_images(output):
"""Extract images from output, handling both dict and SimpleNamespace types.
def _cleanup_distributed():
"""Clean up distributed environment and GPU resources."""
if dist.is_initialized():
dist.destroy_process_group()
The output structure varies depending on serialization path:
- Direct memory: SimpleNamespace with .images attribute
- SHM serialization: dict with "images" key (dataclass converted via asdict)
- Wrapped output: SimpleNamespace(output=...) which needs unwrapping
"""
# Check if output has direct images attribute (diffusion mode)
if hasattr(output, "images") and output.images:
return output.images
for key in ["MASTER_ADDR", "MASTER_PORT", "RANK", "WORLD_SIZE", "LOCAL_RANK"]:
os.environ.pop(key, None)
# Check request_output for pipeline mode
if output.request_output is None:
return None
gc.collect()
if isinstance(output.request_output, list) and len(output.request_output) == 0:
return None
if torch.cuda.is_available():
torch.cuda.empty_cache()
torch.cuda.synchronize()
item = output.request_output[0]
time.sleep(5)
# Handle wrapped SimpleNamespace (e.g. from omni_stage.py)
# Some items are wrapped as SimpleNamespace(request_id=..., output=...)
while hasattr(item, "output") and not hasattr(item, "images"):
item = item.output
if item is None:
return None
# Handle both dict (from SHM serialization) and object (direct) types
if isinstance(item, dict):
return item.get("images")
return getattr(item, "images", None)
def _run_baseline(model_name: str, dtype: torch.dtype, attn_backend: str, height: int, width: int, seed: int):
"""Run baseline inference (no SP)."""
baseline_parallel_config = DiffusionParallelConfig(ulysses_degree=1, ring_degree=1)
baseline = Omni(
model=model_name,
parallel_config=baseline_parallel_config,
dtype=dtype,
attention_backend=attn_backend,
)
try:
outputs = baseline.generate(
PROMPT,
height=height,
width=width,
num_inference_steps=4,
guidance_scale=0.0,
generator=torch.Generator(get_device_name()).manual_seed(seed),
num_outputs_per_prompt=1,
)
return outputs[0].request_output[0].images
finally:
baseline.close()
_cleanup_distributed()
def _run_sp(
model_name: str,
dtype: torch.dtype,
attn_backend: str,
height: int,
width: int,
seed: int,
ulysses_degree: int,
ring_degree: int,
):
"""Run SP inference."""
sp_parallel_config = DiffusionParallelConfig(ulysses_degree=ulysses_degree, ring_degree=ring_degree)
sp = Omni(
model=model_name,
parallel_config=sp_parallel_config,
dtype=dtype,
attention_backend=attn_backend,
)
try:
outputs = sp.generate(
PROMPT,
height=height,
width=width,
num_inference_steps=4,
guidance_scale=0.0,
generator=torch.Generator(get_device_name()).manual_seed(seed),
num_outputs_per_prompt=1,
)
return outputs[0].request_output[0].images
finally:
sp.close()
_cleanup_distributed()
@pytest.mark.parametrize("model_name", models)
@pytest.mark.parametrize("dtype", [torch.bfloat16])
@pytest.mark.parametrize("attn_backend", ["sdpa"])
def test_baseline_only(model_name: str, dtype: torch.dtype, attn_backend: str):
"""Test baseline inference only (no SP)."""
height = 256
width = 256
seed = 42
images = _run_baseline(model_name, dtype, attn_backend, height, width, seed)
assert images is not None
assert len(images) == 1
assert images[0].width == width
assert images[0].height == height
@pytest.mark.parametrize("model_name", models)
@pytest.mark.parametrize("dtype", [torch.bfloat16])
@pytest.mark.parametrize("attn_backend", ["sdpa"])
def test_sp_ulysses2_only(model_name: str, dtype: torch.dtype, attn_backend: str):
"""Test SP inference only (ulysses=2)."""
if device_count() < 2:
pytest.skip(f"Test requires 2 GPUs but only {device_count()} available")
height = 256
width = 256
seed = 42
images = _run_sp(model_name, dtype, attn_backend, height, width, seed, ulysses_degree=2, ring_degree=1)
assert images is not None
assert len(images) == 1
assert images[0].width == width
assert images[0].height == height
@pytest.mark.parametrize("model_name", models)
@pytest.mark.parametrize("dtype", [torch.bfloat16])
@pytest.mark.parametrize("attn_backend", ["sdpa"])
def test_sp_ring2_only(model_name: str, dtype: torch.dtype, attn_backend: str):
"""Test SP inference only (ring=2)."""
if device_count() < 2:
pytest.skip(f"Test requires 2 GPUs but only {device_count()} available")
height = 256
width = 256
seed = 42
images = _run_sp(model_name, dtype, attn_backend, height, width, seed, ulysses_degree=1, ring_degree=2)
assert images is not None
assert len(images) == 1
assert images[0].width == width
assert images[0].height == height
@pytest.mark.parametrize("model_name", models)
@pytest.mark.parametrize("ulysses_degree", [1, 2])
@pytest.mark.parametrize("ring_degree", [1, 2])
@pytest.mark.parametrize("dtype", [torch.bfloat16]) # Only test bfloat16 to reduce CI time
@pytest.mark.parametrize("dtype", [torch.bfloat16])
@pytest.mark.parametrize("attn_backend", ["sdpa"])
def test_sequence_parallel(
model_name: str,
@@ -100,214 +201,60 @@ def test_sequence_parallel(
"""Compare baseline (ulysses_degree=1) vs SP (ulysses_degree>1) outputs."""
if ulysses_degree <= 1 and ring_degree <= 1:
pytest.skip(
"This test compares ulysses_degree * ring_degree = 1 vs ulysses_degree * ring_degree > 1; provide ulysses_degree or ring_degree>1."
"This test compares ulysses_degree * ring_degree = 1 vs ulysses_degree * ring_degree > 1; "
"provide ulysses_degree or ring_degree>1."
)
# Skip if not enough GPUs available for SP run
if device_count() < ulysses_degree * ring_degree:
pytest.skip(f"Test requires {ulysses_degree * ring_degree} GPUs but only {device_count()} available")
sp_size = ulysses_degree * ring_degree
if device_count() < sp_size:
pytest.skip(f"Test requires {sp_size} GPUs but only {device_count()} available")
# Use minimal settings for fast testing
height = 256
width = 256
num_inference_steps = 4 # Minimal steps for fast test
seed = 42
# Step 1: Baseline (no Ulysses sequence parallel)
baseline_parallel_config = DiffusionParallelConfig(ulysses_degree=1, ring_degree=1)
baseline = Omni(
model=model_name,
parallel_config=baseline_parallel_config,
dtype=dtype,
attention_backend=attn_backend,
)
try:
outputs = baseline.generate(
PROMPT,
height=height,
width=width,
num_inference_steps=num_inference_steps,
guidance_scale=0.0,
generator=torch.Generator(get_device_name()).manual_seed(seed),
num_outputs_per_prompt=1,
)
baseline_images = outputs[0].request_output[0].images
finally:
baseline.close()
if dist.is_initialized():
dist.destroy_process_group()
for key in ["MASTER_ADDR", "MASTER_PORT", "RANK", "WORLD_SIZE", "LOCAL_RANK"]:
os.environ.pop(key, None)
time.sleep(2) # Wait for resources to release
baseline_images = _run_baseline(model_name, dtype, attn_backend, height, width, seed)
assert baseline_images is not None and len(baseline_images) == 1
assert baseline_images is not None
assert len(baseline_images) == 1
assert baseline_images[0].width == width
assert baseline_images[0].height == height
sp_images = _run_sp(model_name, dtype, attn_backend, height, width, seed, ulysses_degree, ring_degree)
assert sp_images is not None and len(sp_images) == 1
# Step 2: SP (Ulysses-SP + Ring-SP)
sp_parallel_config = DiffusionParallelConfig(ulysses_degree=ulysses_degree, ring_degree=ring_degree)
sp = Omni(
model=model_name,
parallel_config=sp_parallel_config,
dtype=dtype,
attention_backend=attn_backend,
)
try:
outputs = sp.generate(
PROMPT,
height=height,
width=width,
num_inference_steps=num_inference_steps,
guidance_scale=0.0,
generator=torch.Generator(get_device_name()).manual_seed(seed),
num_outputs_per_prompt=1,
)
sp_images = outputs[0].request_output[0].images
finally:
sp.close()
if dist.is_initialized():
dist.destroy_process_group()
for key in ["MASTER_ADDR", "MASTER_PORT", "RANK", "WORLD_SIZE", "LOCAL_RANK"]:
os.environ.pop(key, None)
time.sleep(2)
assert sp_images is not None
assert len(sp_images) == 1
assert sp_images[0].width == width
assert sp_images[0].height == height
# Step 3: Compare outputs
mean_abs_diff, max_abs_diff = _diff_metrics(baseline_images[0], sp_images[0])
# FP16/BF16 may differ slightly due to different computation order under parallelism.
if dtype in (torch.float16, torch.bfloat16):
mean_threshold = 2e-2
max_threshold = 2e-1
else:
mean_threshold = 1e-2
max_threshold = 1e-1
print(
"Image diff stats (baseline ulysses_degree*ring_degree=1 vs SP): "
f"mean_abs_diff={mean_abs_diff:.6e}, max_abs_diff={max_abs_diff:.6e}; "
f"thresholds: mean<={mean_threshold:.6e}, max<={max_threshold:.6e}; "
f"ulysses_degree={ulysses_degree}, ring_degree={ring_degree}, dtype={dtype}"
)
mean_threshold = 2e-2
max_threshold = 2e-1
assert mean_abs_diff <= mean_threshold and max_abs_diff <= max_threshold, (
f"Image diff exceeded threshold: mean_abs_diff={mean_abs_diff:.6e}, max_abs_diff={max_abs_diff:.6e} "
f"(thresholds: mean<={mean_threshold:.6e}, max<={max_threshold:.6e}); "
f"ulysses_degree={ulysses_degree}, ring_degree={ring_degree}, dtype={dtype}"
f"Image diff exceeded threshold: mean={mean_abs_diff:.6e}, max={max_abs_diff:.6e}"
)
@pytest.mark.parametrize("model_name", models)
@pytest.mark.parametrize("dtype", [torch.bfloat16])
@pytest.mark.parametrize("attn_backend", ["sdpa"])
def test_sequence_parallel_ulysses_sp_only(
model_name: str,
dtype: torch.dtype,
attn_backend: str,
):
"""Test sequence parallel with ulysses_degree=4, ring_degree=1, and the image size (332x332) where the sequence length is NOT divisible by sp_size."""
def test_sequence_parallel_ulysses4(model_name: str, dtype: torch.dtype, attn_backend: str):
"""Test SP with ulysses_degree=4."""
ulysses_degree = 4
ring_degree = 1
# Skip if not enough GPUs available for SP run
if device_count() < ulysses_degree * ring_degree:
pytest.skip(f"Test requires {ulysses_degree * ring_degree} GPUs but only {device_count()} available")
# (272/8) * (272/8) = 17 * 17 = 289 Not divisible by sp_size=4
height = 272
width = 272
num_inference_steps = 4 # Minimal steps for fast test
seed = 42
# Step 1: Baseline (no Ulysses sequence parallel)
baseline_parallel_config = DiffusionParallelConfig(ulysses_degree=1, ring_degree=1)
baseline = Omni(
model=model_name,
parallel_config=baseline_parallel_config,
dtype=dtype,
attention_backend=attn_backend,
)
try:
outputs = baseline.generate(
PROMPT,
height=height,
width=width,
num_inference_steps=num_inference_steps,
guidance_scale=0.0,
generator=torch.Generator(get_device_name()).manual_seed(seed),
num_outputs_per_prompt=1,
)
baseline_images = outputs[0].request_output[0].images
finally:
baseline.close()
if dist.is_initialized():
dist.destroy_process_group()
for key in ["MASTER_ADDR", "MASTER_PORT", "RANK", "WORLD_SIZE", "LOCAL_RANK"]:
os.environ.pop(key, None)
time.sleep(2) # Wait for resources to release
baseline_images = _run_baseline(model_name, dtype, attn_backend, height, width, seed)
assert baseline_images is not None and len(baseline_images) == 1
assert baseline_images is not None
assert len(baseline_images) == 1
assert baseline_images[0].width == width
assert baseline_images[0].height == height
sp_images = _run_sp(model_name, dtype, attn_backend, height, width, seed, ulysses_degree, ring_degree)
assert sp_images is not None and len(sp_images) == 1
# Step 2: SP (Ulysses-SP + Ring-SP)
sp_parallel_config = DiffusionParallelConfig(ulysses_degree=ulysses_degree, ring_degree=ring_degree)
sp = Omni(
model=model_name,
parallel_config=sp_parallel_config,
dtype=dtype,
attention_backend=attn_backend,
)
try:
outputs = sp.generate(
PROMPT,
height=height,
width=width,
num_inference_steps=num_inference_steps,
guidance_scale=0.0,
generator=torch.Generator(get_device_name()).manual_seed(seed),
num_outputs_per_prompt=1,
)
sp_images = outputs[0].request_output[0].images
finally:
sp.close()
if dist.is_initialized():
dist.destroy_process_group()
for key in ["MASTER_ADDR", "MASTER_PORT", "RANK", "WORLD_SIZE", "LOCAL_RANK"]:
os.environ.pop(key, None)
time.sleep(2)
assert sp_images is not None
assert len(sp_images) == 1
assert sp_images[0].width == width
assert sp_images[0].height == height
# Step 3: Compare outputs
mean_abs_diff, max_abs_diff = _diff_metrics(baseline_images[0], sp_images[0])
# FP16/BF16 may differ slightly due to different computation order under parallelism.
if dtype in (torch.float16, torch.bfloat16):
mean_threshold = 2e-2
max_threshold = 2e-1
else:
mean_threshold = 1e-2
max_threshold = 1e-1
print(
"Image diff stats (baseline ulysses_degree*ring_degree=1 vs SP): "
f"mean_abs_diff={mean_abs_diff:.6e}, max_abs_diff={max_abs_diff:.6e}; "
f"thresholds: mean<={mean_threshold:.6e}, max<={max_threshold:.6e}; "
f"ulysses_degree={ulysses_degree}, ring_degree={ring_degree}, dtype={dtype}"
)
mean_threshold = 2e-2
max_threshold = 2e-1
assert mean_abs_diff <= mean_threshold and max_abs_diff <= max_threshold, (
f"Image diff exceeded threshold: mean_abs_diff={mean_abs_diff:.6e}, max_abs_diff={max_abs_diff:.6e} "
f"(thresholds: mean<={mean_threshold:.6e}, max<={max_threshold:.6e}); "
f"ulysses_degree={ulysses_degree}, ring_degree={ring_degree}, dtype={dtype}"
f"Image diff exceeded threshold: mean={mean_abs_diff:.6e}, max={max_abs_diff:.6e}"
)