Renumbering row will make an unknown not associate with its row (equation), 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
