Does matrix rank makes sense modulo composite $n$?

Georgi Guninski <[email protected]> Sat, 18 Jul 2026 09:13:40 +0300

Newsgroups	gmane.comp.mathematics.pari.devel
Message-ID	<CAGUWgD8LD+6YTcrfgwJcZTFdLs6C5tdLeXSA2AdN=ACH5=47eg@mail.gmail.com>

Both pari and sage fail to compute the rank of matrix modulo composite $n$:
? M=Mod(1,4)*[2,2;2,2]
? matrank(M)
  ***   at top-level: matrank(M)
  ***                 ^----------
  *** matrank: impossible inverse in Fl_inv: Mod(2, 4).

Does matrix rank makes sense modulo composite $n$?