When implementing algorithmic “pick/keep/max” logic, make the selected set deterministic and the ordering explicit—then compute sort/max keys using robust parsing. Apply: - Filter at the source: if a category (e.g., val shard) must never be in a selection, exclude it during construction rather than appending then removing. - Avoid redundant de-dup/sort: if the list you start with (e.g., `range(n)`) is already unique and ordered, don’t add `set()` or extra `sorted()` just to satisfy uniqueness. - Use reliable key extraction for maxima: prefer `Path`/`stem`/`name` and direct `stat().st_mtime` for sort keys; keep parsing aligned with how files are named/saved. Example (ids construction and checkpoint step selection): ```python # Deterministic, minimal ordering ids_to_download = list(range(num)) if VAL_SHARD_INDEX not in ids_to_download: ids_to_download.append(VAL_SHARD_INDEX) ids_to_download.sort() # only if you must re-establish order # Robust parsing + max selection checkpoint_files = list(checkpoint_dir.glob('model_*.pt')) last_step = int(max(f.stem.split('_')[-1] for f in checkpoint_files)) ```