tracel-ai/burn · error

Failed to write weights

Error message

Failed to write weights

What it means

I/O guard in the FID metric's weight downloader: writing the downloaded Inception weights bytes into the newly created cache file failed (e.g., disk full or file removed mid-write), so the download path panics.

Source

Thrown at crates/burn-train/src/metric/vision/fid/weights.rs:28

fn get_cache_dir() -> PathBuf {
    let cache_dir = dirs::cache_dir()
        .expect("Could not get cache directory")
        .join("burn-dataset")
        .join("fid");

    if !cache_dir.exists() {
        create_dir_all(&cache_dir).expect("Failed to create cache directory");
    }

    cache_dir
}

fn download_if_needed(url: &str, cache_path: &PathBuf, message: &str) {
    if !cache_path.exists() {
        let bytes = download_file_as_bytes(url, message);
        let mut file = File::create(cache_path).expect("Failed to create cache file");
        file.write_all(&bytes).expect("Failed to write weights");
    }
}

/// Download and load pretrained pytorch-fid InceptionV3 weights.
///
/// Weights are cached in `~/.cache/burn-dataset/fid/`.
pub fn load_pretrained_weights(mut fid: Fid) -> Fid {
    let cache_dir = get_cache_dir();
    let cache_path = cache_dir.join("pt-inception-2015-12-05-6726825d.pth");

    download_if_needed(
        INCEPTION_WEIGHTS_URL,
        &cache_path,
        "Downloading InceptionV3 weights for FID...",
    );

    // PyTorch keys use "Conv2d_1a_3x3.*" etc, our model nests them under "extractor.*"
    let mut store = PytorchStore::from_file(&cache_path)

View on GitHub (pinned to d16f7ba2ed)

Solutions

1. Verify sufficient disk space for the weights file
2. Check the cache directory was not deleted concurrently
3. Retry the download after resolving the filesystem issue

When it happens

Trigger: Thrown at crates/burn-train/src/metric/vision/fid/weights.rs:28 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of tracel-ai/burn@d16f7ba2ed (2026-09-05). Data as JSON: /api/errors/3e71e2f050d975db. Report an issue: GitHub.