rohitg00/ai-engineering-from-scratch · error · ValueError

No trainable parameters. Did you freeze the head as well?

Error message

No trainable parameters. Did you freeze the head as well?

What it means

Error "No trainable parameters. Did you freeze the head as well?" thrown in rohitg00/ai-engineering-from-scratch.

Source

Thrown at phases/19-capstone-projects/38-classifier-finetuning/code/main.py:396

@dataclass
class TrainReport:
    losses: List[float]
    final_loss: float
    trainable: int


def train_classifier(
    model: Classifier,
    train_loader: DataLoader,
    epochs: int,
    lr: float,
    seed: int,
) -> TrainReport:
    torch.manual_seed(seed)
    params = [p for p in model.parameters() if p.requires_grad]
    if not params:
        raise ValueError("No trainable parameters. Did you freeze the head as well?")
    opt = torch.optim.Adam(params, lr=lr)
    losses: List[float] = []
    model.train()
    for _ in range(epochs):
        epoch_loss = 0.0
        n_batches = 0
        for ids, mask, y in train_loader:
            logits = model(ids, mask)
            loss = F.cross_entropy(logits, y)
            opt.zero_grad()
            loss.backward()
            opt.step()
            epoch_loss += float(loss.item())
            n_batches += 1
        losses.append(epoch_loss / max(n_batches, 1))
    return TrainReport(losses=losses, final_loss=losses[-1], trainable=trainable_params(model))

View on GitHub (pinned to 39ea8a1c6d)

When it happens

Trigger: Thrown at phases/19-capstone-projects/38-classifier-finetuning/code/main.py:396 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of rohitg00/ai-engineering-from-scratch@39ea8a1c6d (2026-08-26). Data as JSON: /api/errors/caa58e0b00067ad9. Report an issue: GitHub.