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hao-ai-lab-FastVideo/examples/inference/basic/basic_fasth3.py
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# SPDX-License-Identifier: Apache-2.0
"""Few-step video+audio generation with the DMD2-distilled MiniMax H3 preview.
FastVideo/FastVideo-Minimax-FastH3-Preview-v0.1 is a 4-step distillation of
MiniMaxAI/MiniMax-H3 (data-free DMD2): it walks a 4-step grid on the release
sampler's shift-12 schedule instead of the base model's 50 steps, generating
synchronized video and audio in one pipeline call.
The student was trained with block-sparse video attention (VSA, 64-token
tiles) and its checkpoint carries the trained sparse-gate parameters
(``attn.to_gate_compress``), so this script always runs the VSA-H3 attention
backend. At the default ``--vsa-sparsity 0.0`` the attention math is exactly
dense (every tile is selected); raise the sparsity for additional speedup.
"""
from __future__ import annotations
import argparse
import os
from pathlib import Path
from fastvideo import VideoGenerator
from fastvideo.api import (
CompileConfig,
EngineConfig,
GenerationRequest,
GeneratorConfig,
OffloadConfig,
OutputConfig,
ParallelismConfig,
PipelineSelection,
SamplingConfig,
)
def parse_args() -> argparse.Namespace:
parser = argparse.ArgumentParser(description=__doc__)
parser.add_argument("--model-path", default="FastVideo/FastVideo-Minimax-FastH3-Preview-v0.1")
# The HF repo is private while the MiniMax H3 Community License review
# completes; until it flips public, pass --model-path with a local
# snapshot of the release instead (e.g. the team export at
# /mnt/lustre/vlm-wlsaidhi/fastvideo/exports/FastVideo-Minimax-FastH3-Preview-v0.1).
parser.add_argument("--prompt", required=True)
parser.add_argument("--output", default="outputs/fasth3")
parser.add_argument("--height", type=int, default=768)
parser.add_argument("--width", type=int, default=1344)
parser.add_argument("--num-frames", type=int, default=124)
# num_inference_steps counts sigma-GRID POINTS, matching the base model's
# convention ("50 steps" = a 50-point grid = 49 transformer forwards). The
# student's distilled 4-step grid is 4 FORWARDS, i.e. a 5-point grid
# (t = 1000, 750, 500, 250 -> 0 on the shift-12 schedule) — so the correct
# default here is 5. Other grids are off-distribution.
parser.add_argument("--steps",
type=int,
default=5,
help="num_inference_steps = sigma-grid points; N points run N-1 denoising "
"forwards. 5 (default) is the distilled 4-forward grid")
parser.add_argument("--seed", type=int, default=0)
parser.add_argument("--num-gpus", type=int, default=4)
parser.add_argument("--vsa-sparsity",
type=float,
default=0.0,
help="Run-level VSA sparsity in [0, 1). 0.0 (default) selects every tile, which is "
"exactly dense attention; the student was trained at 0.9")
# 64 is the trained contract: the student was TRAINED with 64-token
# (4,4,4) tiles, and its to_gate_compress gates were learned against
# pooling at that granularity — keep 64 unless you are ablating.
parser.add_argument("--vsa-tile-size",
type=int,
choices=(64, 256),
default=64,
help="VSA-H3 tile size in tokens; 64 (default) is what the student was trained "
"with and runs the native Triton block-sparse path, 256 is the FA4-CuTe-capable "
"geometry for ablations")
parser.add_argument("--vsa-kernel",
choices=("triton", "sm100a"),
default="triton",
help="Block-sparse kernel for the tile-64 attention forward: triton (default, "
"portable fwd+bwd) or sm100a — the opt-in Blackwell CUDA forward "
"(fastvideo_kernel.block_sparse_attn_sm100a). sm100a needs an sm_100 GPU and a "
"fastvideo-kernel build that carries the extension; if a precondition fails at "
"run time the attention layer logs one warning and falls back to Triton. Only "
"meaningful with --vsa-tile-size 64")
parser.add_argument("--torch-compile", action="store_true", help="torch.compile the DiT transformer path")
parser.add_argument("--compile-mode",
default=None,
help='torch.compile mode, e.g. "reduce-overhead" for CUDA graphs')
parser.add_argument("--inference-torch-compile",
action="store_true",
help="regional fullgraph torch.compile of each DiT block after load. NOTE: this "
"script always runs the VSA-H3 backend, which is not fullgraph-traceable — the "
"loader logs one warning and keeps the transformer eager. The flag is exposed "
"here to exercise exactly that guard")
parser.add_argument("--repeats",
type=int,
default=1,
help="generate N times; with --torch-compile the first run pays "
"compilation, so steady-state is the last repeat")
return parser.parse_args()
def main() -> None:
args = parse_args()
output_dir = Path(args.output)
output_dir.mkdir(parents=True, exist_ok=True)
if args.vsa_kernel == "sm100a":
# The attention backend reads FASTVIDEO_VSA_SM100A per forward; set it
# before the pipeline boots so spawned GPU workers inherit it. The
# kernel is forward-only and inference runs under no-grad, so every
# denoising forward qualifies for the CUDA route.
os.environ["FASTVIDEO_VSA_SM100A"] = "1"
# Boot-time run configuration, folded into FastVideoArgs (the same route
# examples/inference/basic/basic_minimax_h3_t2v.py uses for sparsity):
# - attention_backend: the checkpoint carries trained to_gate_compress
# gates, which only exist under the VSA-H3 backend — a dense-backend
# load would reject them as unexpected weights. Layers that do not
# support VSA-H3 (e.g. the token refiner) fall back to flash attention.
# - VSA_tile_size: forwarded even at sparsity 0.0 because the gate-compress
# branch pools per tile, and the gates were trained at 64 tokens/tile.
experimental: dict[str, object] = {
"attention_backend": "VIDEO_SPARSE_ATTN_H3",
"VSA_tile_size": args.vsa_tile_size,
}
if args.vsa_sparsity > 0.0:
experimental["VSA_sparsity"] = args.vsa_sparsity
if args.inference_torch_compile:
experimental["inference_torch_compile"] = True
generator = VideoGenerator.from_config(
GeneratorConfig(
model_path=args.model_path,
pipeline=PipelineSelection(experimental=experimental),
engine=EngineConfig(
num_gpus=args.num_gpus,
use_fsdp_inference=args.num_gpus > 1,
parallelism=ParallelismConfig(tp_size=1, sp_size=args.num_gpus),
offload=OffloadConfig(
dit=False,
dit_layerwise=False,
text_encoder=True,
vae=True,
pin_cpu_memory=False,
),
compile=CompileConfig(
enabled=args.torch_compile,
mode=args.compile_mode,
),
),
))
try:
request = GenerationRequest(
prompt=args.prompt,
negative_prompt="",
sampling=SamplingConfig(
height=args.height,
width=args.width,
num_frames=args.num_frames,
fps=24,
num_inference_steps=args.steps,
# the base model is guidance-distilled; the student inherits it
guidance_scale=1.0,
batch_cfg=False,
seed=args.seed,
),
output=OutputConfig(
output_path=str(output_dir / "fasth3.mp4"),
save_video=True,
return_frames=False,
),
)
result = generator.generate(request)
print(f"Output written to: {result.video_path}")
if result.generation_time is not None:
# machine-readable: benchmark harnesses parse this line to separate
# generation from model-load time (last occurrence = steady state)
print(f"Generation time: {result.generation_time:.2f}s")
for _ in range(args.repeats - 1):
result = generator.generate(request)
if result.generation_time is not None:
print(f"Generation time: {result.generation_time:.2f}s")
finally:
generator.shutdown()
if __name__ == "__main__":
main()