The error is at line 1023 of "plog.c". --------------- An unhandled exception of type 'System.NullReferenceException' occurred in Unknown Module.
Additional information: Object reference not set to an instance of an object. ---------------- The matrix I am trying to initialize is the stiffness matrix K of finite element methods. Later the dynamical system is solved as (I + Dt*K) U(t+1) = U(t) + Dt.F(t) by calling KSPSolve. Any idea how to set the number of local rows? I am running the code on PC now, but want to keep MatCreateMPIAIJ in it. Xiaoxu ----- Original Message ----- From: "Barry Smith" <bsmith at mcs.anl.gov> To: <petsc-users at mcs.anl.gov> Sent: Tuesday, October 03, 2006 8:32 AM Subject: Re: MatCreateMPIAIJ > > > On Mon, 2 Oct 2006, Xiaoxu Wang wrote: > >> Hi, >> >> I am a beginner on PETSC. This is my question about >> MatCreateMPIAIJ. I >> have a sparse matrix and only know the total number of nonzeros each >> row. The >> number of local rows and the number of local columns has been set to >> PETSC_DECIDE. Therefore I don't know the size of each portion and it >> is hard >> to tell d_nnz and o_nnz. I use the total number of nunzeros as d_nnz >> and get >> an allocation error. > > > It would be helpful to know the exact error message: > >> How to deal with this problem? Should I explicitly >> specify the number of local rows and the number of local columns and >> calculate >> d_nnz and o_nnz? Or let PETSC decide the number of local rows and the >> number >> of local columns, and then use another function to get these values? >> Any >> other better solution? > > > You should specifically set the number of local rows and columns and > then > compute the values of d_nnz and o_nnz. How you determine d_nnz and > o_nnz is > problem dependent and depends on what type of discretization you are > using: > finite differences, elements etc. > > > Barry > >> >> Thanks a lot, >> Xiaoxu >> >> > >
