Yes On Jul 31, 2014, at 11:04 AM, Qin Lu <[email protected]> wrote:
> Barry, > > If I understand you correctly, I should number all unknowns owned by a > process contiguously before I construct the matrix, right? > > Thanks, > Qin > > From: Barry Smith <[email protected]> > To: Qin Lu <[email protected]> > Cc: Matthew Knepley <[email protected]>; petsc-users > <[email protected]> > Sent: Thursday, July 31, 2014 10:46 AM > Subject: Re: [petsc-users] Partition of parallel AIJ sparce matrix > > > On Jul 31, 2014, at 9:35 AM, Qin Lu <[email protected]> wrote: > > > Do you mean the user has to reorder both rows and columns (unknowns)? Or > > the renumbering of columns are done by PETSc? > > NO, never reorder the matrix. The degrees of freedom should be reordered to > be contiquous before any matrix is ever created. Then the matrix and > everything else is always computed with regard to this new ordering. > > Barry > > > > > > Matthew's early response said that only rows need to renumbered by the user > > so that they are contiguous for each process. In my case, the order of > > unknowns have been determined before parallel partitioning, is this (just > > renumbering rows) Ok? > > > > Thanks, > > Qin > > > > From: Barry Smith <[email protected]> > > To: Qin Lu <[email protected]> > > Cc: Matthew Knepley <[email protected]>; petsc-users > > <[email protected]> > > Sent: Wednesday, July 30, 2014 7:37 PM > > Subject: Re: [petsc-users] Partition of parallel AIJ sparce matrix > > > > > > On Jul 30, 2014, at 3:59 PM, Qin Lu <[email protected]> wrote: > > > > > Renumbering row will make an unknown not associate with its row > > > (equation), > > > > It is a symmetric reordering. In matrix terms both the rows and columns > > are reordered the same way. In terms of spaces both the domain and range > > spaces are reordered the same way. > > > > Barry > > > > > > > will this affect the solver performance? For example, will the infill > > > pattern change in ILU factorization? > > > > > > Thanks, > > > Qin > > > > > > From: Matthew Knepley <[email protected]> > > > To: Qin Lu <[email protected]> > > > Cc: Barry Smith <[email protected]>; petsc-users > > > <[email protected]> > > > Sent: Wednesday, July 30, 2014 3:50 PM > > > Subject: Re: [petsc-users] Partition of parallel AIJ sparce matrix > > > > > > On Wed, Jul 30, 2014 at 3:30 PM, Qin Lu <[email protected]> wrote: > > > In the context of domain decompostion, if the unknowns are ordered (to > > > reduce the number of infills, for instance) in the way that each > > > subdomain may not own consecutive unknown index, does this mean the > > > partition of the domain will be different from the partition of the > > > matrix? > > > > > > For example, if subdomain 1 (assigned to process 1) owns unknowns 1 and 3 > > > (associated with equation 1 and 3), subdomain 2 (assigned to process 2) > > > owns unknowns 2 and 4 (associated with equation 2 and 4) , how can I make > > > each process own consecutive rows? > > > > > > You renumber the rows once they are partitioned. > > > > > > Matt > > > > > > > > > > > > Thanks, > > > Qin > > > > > > From: Barry Smith <[email protected]> > > > To: Qin Lu <[email protected]> > > > Cc: petsc-users <[email protected]> > > > Sent: Wednesday, July 30, 2014 2:49 PM > > > Subject: Re: [petsc-users] Partition of parallel AIJ sparce matrix > > > > > > > > > On Jul 30, 2014, at 11:08 AM, Qin Lu <[email protected]> wrote: > > > > > > > Hello, > > > > > > > > Does a process have to own consecutive rows of the matrix? For example, > > > > suppose the global AIJ is 4x4, partitioned by 2 processes. Does process > > > > 1 have to own rows 1 and 2, process 2 own rows 3 and 4? > > > > > > Yes > > > > > > > Or process1 may own rows 1 and 3, and process 2 own row 2 and 4? > > > > > > However, the numbering of degrees of freedom is arbitrary. Just renumber > > > you degrees of freedom so the first set is on process 0, the next on > > > process 1 etc. > > > > > > Barry > > > > > > > > > > > > > > Thanks a lot for your help! > > > > > > > > Regards, > > > > Qin > > > > > > > > > > > > > > > > > > > > > -- > > > What most experimenters take for granted before they begin their > > > experiments is infinitely more interesting than any results to which > > > their experiments lead. > > > -- Norbert Wiener > > > > > > > > > > > >
