Do you mean the user has to reorder both rows and columns (unknowns)? Or the renumbering of columns are done by PETSc? 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 > >
