hpcaitech/Open-Sora · error · ValueError

Unknown GAN loss '{self.disc_loss_type}'.

Error message

Unknown GAN loss '{self.disc_loss_type}'.

What it means

The discriminator GAN loss wrapper in vae/losses.py selects its loss function by string: 'hinge', 'vanilla', or 'wgan-gp'. Any other disc_loss_type string falls through to the else and raises ValueError at construction time.

Source

Thrown at opensora/models/vae/losses.py:208


class DiscriminatorLoss(nn.Module):
    def __init__(self, disc_start=2001, disc_factor=1.0, disc_loss_type="hinge"):
        super().__init__()

        assert disc_loss_type in ["hinge", "vanilla", "wgan-gp"]
        self.disc_factor = disc_factor
        self.disc_start = disc_start
        self.disc_loss_type = disc_loss_type

        if self.disc_loss_type == "hinge":
            self.loss_fn = hinge_d_loss
        elif self.disc_loss_type == "vanilla":
            self.loss_fn = vanilla_d_loss
        elif self.disc_loss_type == "wgan-gp":
            self.loss_fn = wgan_gp_loss
        else:
            raise ValueError(f"Unknown GAN loss '{self.disc_loss_type}'.")

    def forward(
        self,
        real_logits,
        fake_logits,
        global_step,
    ):
        if self.disc_factor is not None and self.disc_factor > 0.0:
            disc_factor = adopt_weight(self.disc_factor, global_step, threshold=self.disc_start)
            disc_loss = self.loss_fn(real_logits, fake_logits)
            weighted_discriminator_loss = disc_factor * disc_loss
        else:
            weighted_discriminator_loss = 0

        return weighted_discriminator_loss

View on GitHub (pinned to 7ad6a96a13)

Solutions

  1. Use one of: 'hinge', 'vanilla', or 'wgan-gp' (lowercase, exact)
  2. Check the YAML/config string for typos and casing
  3. If you need another loss, implement it as a function and assign self.loss_fn directly in a subclass

Example fix

# before
loss = DiscLoss(disc_loss_type="logistic")
# after
loss = DiscLoss(disc_loss_type="hinge")
Defensive patterns

Strategy: validation

Validate before calling

assert disc_loss_type in {"hinge", "vanilla", "wgan-gp"}, f"unknown disc_loss_type {disc_loss_type!r}"

Type guard

def is_valid_disc_loss(s: str) -> bool:
    return s in {"hinge", "vanilla", "wgan-gp"}

Prevention

When it happens

Trigger: Constructing the discriminator loss (class wrapping this __init__) with disc_loss_type not in {'hinge','vanilla','wgan-gp'} — e.g. 'wgan', 'logistic', 'ls', or a typo like 'Hinge' (case-sensitive).

Common situations: Copying loss names from other GAN codebases (stylegan 'logistic', 'r1'); case mismatches; config edits while tuning VAE-GAN training.

Related errors

AI-assisted analysis of hpcaitech/Open-Sora@7ad6a96a13 (2026-08-28). Data as JSON: /api/errors/773a73185497d049. Report an issue: GitHub.