parmatch: [mark_partial] now works on "simplified" matrices
parmatch: [mark_partial] now works on "simplified" matrices

We avoid doing some redundant work in the process.

gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml,gerdstolpmann/ocaml