tracel-ai/burn · error

Failed to create cache file

Error message

Failed to create cache file

What it means

I/O guard in the LPIPS weights downloader: creating the cache file to store downloaded LPIPS backbone weights failed, so the download path panics rather than run the metric without its pretrained weights.

Source

Thrown at crates/burn-train/src/metric/vision/lpips/weights.rs:62

/// Get the cache directory for LPIPS weights.
fn get_cache_dir() -> PathBuf {
    let cache_dir = dirs::cache_dir()
        .expect("Could not get cache directory")
        .join("burn-dataset")
        .join("lpips");

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

    cache_dir
}

/// Download file if not cached and return the cache path.
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 weights into an LPIPS module.
///
/// This loads both:
/// 1. ImageNet pretrained backbone weights (VGG16/AlexNet/SqueezeNet)
/// 2. LPIPS trained linear layer weights
///
/// Weights are cached in the user's cache directory to avoid re-downloading.
///
/// # Arguments
///
/// * `lpips` - The LPIPS module to load weights into.
/// * `net` - The network type (determines which weights to download).
///
/// # Returns

View on GitHub (pinned to d16f7ba2ed)

Solutions

1. Verify disk space and permissions in the lpips cache directory
2. Ensure the cache path points to a writable location
3. Pre-download and place the weights file at the cache path

When it happens

Trigger: Thrown at crates/burn-train/src/metric/vision/lpips/weights.rs:62 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/aefb618fcd3f3298. Report an issue: GitHub.