For your purposes you should just use superlu or superlu_dist directly in your code not through PETSc.
Barry There is nothing to be gained by doing it through PETSc. This is not relevant for your use case but I have noted that the unneeded use of MatGetOrdering() should be eliminated https://bitbucket.org/petsc/petsc/issues/211/matgetordering-should-not-be-called-for > On Mar 13, 2018, at 7:04 AM, Natacha BEREUX <natacha.ber...@gmail.com> wrote: > > Hi Barry > Thanks for your answer, > I followed your suggestion (matrix type = MPIAIJ and superlu_dist on a single > processor) but I still get the same problem. > > > Rectangular matrices seem to be forbidden in MatGetOrdering(), whatever > package is used for the LU decomposition > > Here is the output : > ./ex12f -f data/constraints.bin -pc_factor_mat_solver_package superlu_dist > -pc_type lu > > 9 33 9 33 1. 0.3E+02 0.3E+02 0. 0.7E+04 1. 0. > PETSC ERROR: --------------------- Error Message > -------------------------------------------------------------- > PETSC ERROR: Invalid argument > PETSC ERROR: Must be square matrix, rows 33 columns 9 > > > Should I call directly a factorization routine ? Instead of trying to build > a preconditionner ? > > > Best regards, > Natacha > > > On Mon, Mar 12, 2018 at 3:46 PM, Smith, Barry F. <bsm...@mcs.anl.gov> wrote: > > Create the matrix on one process but make it a MPIAIJ matrix (not SeqAIJ > or AIJ) then you should be able to do the factorization with SuperLU_Dist > > Please let us know how it goes, > > Barry > > > > On Mar 12, 2018, at 4:35 AM, Natacha BEREUX <natacha.ber...@gmail.com> > > wrote: > > > > Dear Petsc user's > > > > I am trying to use SuperLU_dist to compute LU decomposition of a non-square > > matrix. > > > > My purpose is to build a basis of the nullspace of a matrix C . This matrix > > stores constraints (i.e. linear relationships between degrees of freedom): > > it is thus rectangular (size 9 x 33) and not square > > I need to get the L U factors of C^T which is a tall skinny matrix. > > It is possible when using directly SuperLu or SuperLU_dist > > But when I use Petsc interface to SuperLU I get the following error : > > > > PETSC ERROR: Invalid argument > > PETSC ERROR: Must be square matrix, rows 9 columns 33 > > PETSC ERROR: See http://www.mcs.anl.gov/petsc/documentation/faq.html for > > trouble shooting. > > PETSC ERROR: Petsc Release Version 3.8.3, Dec, 09, 2017 > > PETSC ERROR: #1 MatGetOrdering() line 243 in > > /home/H03755/Librairies/petsc-3.8.3/src/mat/order/sorder.c > > PETSC ERROR: #2 PCSetUp_LU() line 84 in > > /home/H03755/Librairies/petsc-3.8.3/src/ksp/pc/impls/factor/lu/lu.c > > PETSC ERROR: #3 PCSetUp() line 924 in > > /home/H03755/Librairies/petsc-3.8.3/src/ksp/pc/interface/precon.c > > PETSC ERROR: #4 KSPSetUp() line 381 in > > /home/H03755/Librairies/petsc-3.8.3/src/ksp/ksp/interface/itfunc.c > > PETSC ERROR: #5 KSPSolve() line 612 in > > /home/H03755/Librairies/petsc-3.8.3/src/ksp/ksp/interface/itfunc.c > > PETSC ERROR: #6 User provided function() line 0 in User file > > > > The use of non-square matrices is forbidden. > > > > Is there a way to specify that I want to use a rectangular matrix ? How can > > I proceed to call SuperLU through PETSc with a rectangular matrix ? > > > > Thanks a lot for your help > > Best regards, > > > > Natacha > >