Function subfield_ntt_batch 

pub fn subfield_ntt_batch<S, F>(mat: RowMajorMatrix<S>) -> RowMajorMatrix<F>
where
    S: ButterflyField,
    F: ButterflyField + From<S>,

Evaluate each column of a subfield message on the subspace of the wider level.

Widening the message first pays the wide element size at every layer. The widest layers do not need it: their twiddles map the subfield into itself.

The layers left over run the tower transform, not whichever backend is fastest wide.

Panics

Panics if the height is not a power of two. Panics if the domain dimension exceeds the bit width of the wider level.