pub fn program_third_contracted<const K: usize, P: RowProgram<K> + ?Sized>(
prog: &P,
row: usize,
dir: &[f64; K],
) -> Result<[[f64; K]; K], String>Expand description
Derive the row_third_contracted(dir) channel Σ_c ℓ_{abc} dir_c from a
RowProgram at the one-seed scalar crate::jet_scalar::OneSeed, WITHOUT
materialising the dense t3.