Model checkpoint resolution and caching for eval metrics.

Single public function — :func:ensure_checkpoint — that hands a metric a local path to its weights, downloading on miss. Three source kinds:

an existing local path → returned as-is;
an HTTP(S) URL → downloaded to get_cache_dir() / name via huggingface_hub.http_get (resume + retries built in);
an HF repo id ("org/repo") → :func:huggingface_hub.hf_hub_download if filename is given, else :func:huggingface_hub.snapshot_download. name is ignored in HF mode — HF manages its own cache key under ~/.cache/huggingface/hub.

All download paths are filelock-safe (cooperative across threads, processes, and SLURM ranks) via :func:fastvideo.utils.get_lock.

`fastvideo.eval.models.get_lock`

get_lock(model_name_or_path: str)

`fastvideo.eval.models.get_cache_dir`

get_cache_dir() -> Path

Eval cache root.

Layout::

get_cache_dir() / models /   ← URL-fetched checkpoints (LAION head,
                               AMT, GRiT, …)
get_cache_dir() / torch  /   ← redirected ``TORCH_HOME`` (DINO etc.)
get_cache_dir() / clip   /   ← passed as ``download_root`` to
                               ``clip.load(...)`` callsites
~/.cache/huggingface/hub /   ← left at HF's default; widely shared
                               with other ML projects

Override priority: FASTVIDEO_EVAL_CACHE > ${FASTVIDEO_CACHE_ROOT}/eval.

Metric authors writing new code: when wrapping a third-party loader that has its own cache convention (CLIP's download_root, pyiqa's cache_dir, etc.), pass str(get_cache_dir() / "<library>") so users get a single FASTVIDEO_EVAL_CACHE knob to redirect them all.

Source

def get_cache_dir() -> Path:
    """Eval cache root.

    Layout::

        get_cache_dir() / models /   ← URL-fetched checkpoints (LAION head,
                                       AMT, GRiT, …)
        get_cache_dir() / torch  /   ← redirected ``TORCH_HOME`` (DINO etc.)
        get_cache_dir() / clip   /   ← passed as ``download_root`` to
                                       ``clip.load(...)`` callsites
        ~/.cache/huggingface/hub /   ← left at HF's default; widely shared
                                       with other ML projects

    Override priority: ``FASTVIDEO_EVAL_CACHE`` > ``${FASTVIDEO_CACHE_ROOT}/eval``.

    Metric authors writing new code: when wrapping a third-party loader
    that has its own cache convention (CLIP's ``download_root``, pyiqa's
    ``cache_dir``, etc.), pass ``str(get_cache_dir() / "<library>")`` so
    users get a single ``FASTVIDEO_EVAL_CACHE`` knob to redirect them all.
    """
    return Path(envs.FASTVIDEO_EVAL_CACHE.get())

`fastvideo.eval.models.ensure_checkpoint`

ensure_checkpoint(name: str, source: str, filename: str | None = None) -> str

Resolve a model checkpoint path, downloading on miss.

See module docstring for the full source contract. name is used only as the local cache filename for URL sources; ignored otherwise.

Source

def ensure_checkpoint(
    name: str,
    source: str,
    filename: str | None = None,
) -> str:
    """Resolve a model checkpoint path, downloading on miss.

    See module docstring for the full source contract. *name* is used
    only as the local cache filename for URL sources; ignored otherwise.
    """
    if os.path.exists(source):
        return source

    if source.startswith(("http://", "https://")):
        return _ensure_url(name, source)

    if "/" in source:
        return _ensure_hf(source, filename)

    raise ValueError(f"Cannot resolve checkpoint: source {source!r} is neither a "
                     "path, URL, nor HF repo id")