> On 17 Feb 2023, at 8:56 AM, Stefano Zampini <[email protected]> wrote: > > > On Fri, Feb 17, 2023, 10:43 user_gong Kim <[email protected] > <mailto:[email protected]>> wrote: >> Hello, >> >> I have a question about rank of matrix. >> At the problem >> Au = b, >> >> In my case, sometimes global matrix A is not full rank. >> In this case, the global matrix A is more likely to be singular, and if it >> becomes singular, the problem cannot be solved even in the case of the >> direct solver. >> I haven't solved the problem with an iterative solver yet, but I would like >> to ask someone who has experienced this kind of problem. >> >> 1. If it is not full rank, is there a numerical technique to solve it by >> catching rows and columns with empty ranks in advance? >> >> 2.If anyone has solved it in a different way than the above numerical >> analysis method, please tell me your experience. >> >> Thanks, >> Hyung Kim > > > My experience with this is usually associated to reading a book and find the > solution I'm looking for.
On top of that, some exact factorization packages can solve singular systems, unlike what you are stating. E.g., MUMPS, together with the option -mat_mumps_icntl_24, see https://mumps-solver.org/doc/userguide_5.5.1.pdf Thanks, Pierre
