Constant MIN_TRAINED_DICT_SIZE 

pub const MIN_TRAINED_DICT_SIZE: usize = finalize::DICT_SIZE_MIN /* 256usize */;

Available on crate feature dict-builder only.

Smallest dict_size a dictionary is trained or finalized into (upstream zstd ZDICT_DICTSIZE_MIN).

Use it to reject an impossible dict_size before spending the corpus. A size at or above it can still be too small once the entropy tables the samples produce are built, which only training can tell.