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hao-ai-lab-FastVideo/fastvideo/tests/train/methods/test_wan_causal_tfsft.py

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# SPDX-License-Identifier: Apache-2.0
"""Per-method GPU smoke test: ``WanCausalModel`` + ``TeacherForcingSFTMethod``.
Mirrors ``test_wan_causal_dfsft.py``. Teacher forcing concatenates a clean
context copy of every frame inside the causal transformer (``clean_x``) and
denoises the current block while attending to *clean* history. This test
exercises the ``clean_x`` path end-to-end: forward, finite loss, and nonzero
gradients reaching the first transformer block.
"""
from __future__ import annotations
import os
os.environ.setdefault("MASTER_ADDR", "localhost")
os.environ.setdefault("MASTER_PORT", "29518")
from pathlib import Path
import pytest
import torch
from fastvideo.train.methods.fine_tuning.tfsft import (
TeacherForcingSFTMethod, )
from fastvideo.train.models.wan import WanCausalModel
from fastvideo.train.utils.config import load_run_config
_FIXTURE = str(Path(__file__).resolve().parent.parent / "fixtures" / "wan_causal_t2v_tfsft_min.yaml")
def _build_synthetic_batch(
device: torch.device,
dtype: torch.dtype,
) -> dict[str, torch.Tensor]:
batch_size = 1
return {
"text_embedding": torch.randn(batch_size, 16, 4096, device=device, dtype=dtype),
"text_attention_mask": torch.ones(batch_size, 16, device=device),
"vae_latent": torch.randn(batch_size, 16, 6, 8, 8, device=device, dtype=dtype),
}
@pytest.mark.usefixtures("distributed_setup")
def test_wan_causal_tfsft_single_train_step(monkeypatch: pytest.MonkeyPatch) -> None:
if not torch.cuda.is_available():
pytest.skip("requires CUDA")
cfg = load_run_config(_FIXTURE)
device = torch.device("cuda:0")
dtype = torch.bfloat16
monkeypatch.setattr(
"fastvideo.train.utils.dataloader."
"build_parquet_t2v_train_dataloader",
lambda *args, **kwargs: None,
)
model = WanCausalModel(
init_from=cfg.models["student"]["init_from"],
training_config=cfg.training,
trainable=True,
)
model.transformer = model.transformer.to(device=device, dtype=dtype)
method = TeacherForcingSFTMethod(
cfg=cfg,
role_models={"student": model},
)
method.on_train_start()
batch = _build_synthetic_batch(device, dtype)
loss_map, outputs, _metrics = method.single_train_step(batch, iteration=0)
loss = loss_map["total_loss"]
assert torch.is_tensor(loss), "total_loss must be a torch.Tensor"
assert torch.isfinite(loss).item(), (f"total_loss is not finite: {loss.item()}")
method.backward(loss_map, outputs, grad_accum_rounds=1)
blocks = getattr(model.transformer, "blocks", None)
assert blocks is not None and len(blocks) > 0, ("CausalWanTransformer is expected to expose ``.blocks``")
layer0 = blocks[0]
trainable = [p for p in layer0.parameters() if p.requires_grad]
assert len(trainable) > 0, "layer 0 has no trainable parameters"
for i, p in enumerate(trainable):
assert p.grad is not None, f"layer 0 param[{i}] has None grad"
assert torch.isfinite(p.grad).all().item(), (f"layer 0 param[{i}] grad contains NaN/Inf")
any_nonzero = any(p.grad.detach().float().norm().item() > 0.0 for p in trainable)
assert any_nonzero, ("all layer-0 grads are exactly zero; backward did not "
"reach the first transformer block")
# Teacher forcing must build its own (concatenated) attention mask and
# must not have constructed the diffusion-forcing mask.
assert model.transformer.teacher_forcing_block_mask is not None, ("teacher-forcing mask was not constructed")
assert model.transformer.block_mask is None, ("diffusion-forcing mask should not be built on the TF path")