Question: Where is the cache of the downloaded data set?

[kojix2]

Cache directory

The default cache directory depends on the operating system.

OS	ENV	default path
Linux	XDG_CACHE_HOME	~/.cache
macOS		~/Library/Caches
Windows	LOCALAPPDATA	~/AppData/Local

See cache-path.rb.

The path of each dataset is obtained by calling the private method Datasets::Dataset#cache_dir_path

Datasets::MNIST.new.send("cache_dir_path")
# => #<Pathname:/home/kojix2/.cache/red-datasets/mnist-train>

These are internal APIs and are subject to change in the future.