It is currently Thu Dec 14, 2017 9:49 am


All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 1 post ] 
Author Message
 Post subject: Positive-indefinite rank deficient matrix
PostPosted: Tue Jul 05, 2016 9:04 am 

Joined: Tue Jul 05, 2016 8:46 am
Posts: 1
Real Name: Computational Scientist, UT Ausin, ICES
Began Programming in MUMPS: 03 Jul 2016
Hi all,

I am solving a matrix problem that corresponds to doubly periodic boundary
condition in a FEM representation. It leads to a positive-indefinite rank deficient matrix,
the null space dimension is one, and it's a vector of some constant C, I think. As far as I am thinking, the system can be written Ax=B, but since the boundaries, there is a null vector y, such that A(x+y) = B, for some Ay=0. I would like to solve the system under the global constraint that y (or, the effect of y on the solution x) vanishes. I am not sure how to make this happen in MUMPS. I think in petsc something like KSPSetNullSpace() might work...?

Right now I set:

MatMumpsSetIcntl (F, 7, 2);

MatMumpsSetIcntl (F, 24, 1);

MatMumpsSetCntl (F, 1, 0.1);

MatMumpsSetCntl (F,4, 1.E-6);

But the solution I get back is still off by a constant. Is there a way of determining a unique solution?

Thanks,
Craig


Top
Offline Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 1 post ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Theme created StylerBB.net