Definition rowval_gen m U :=
<<\matrix_ik
mxvec (\matrix_(i < m, k < d) (row i (val_gen U) *m A ^+ k)) 0 ik>>%MS.

Lemma submx_rowval_gen m1 m2 (U : 'M_(m1, n)) (V : 'M_(m2, nA)) :
(U <= rowval_gen V)%MS = (in_gen U <= V)%MS.