Thanks for your reply. For GMRES, I create a ghost vector and give it to KSPSolve. For Slepc, it only takes the shell matrix for EPSSetOperators. Suppose the shell matrix of the eigensolver defines MatMult(Mat m ,Vec x, Vec y), how does it know Vec x is a ghost vector and how many ghost cells there are?
Thanks, Feng ________________________________ From: Matthew Knepley <[email protected]> Sent: 21 September 2022 11:58 To: feng wang <[email protected]> Cc: [email protected] <[email protected]> Subject: Re: [petsc-users] Slepc, shell matrix, parallel, halo exchange On Wed, Sep 21, 2022 at 7:41 AM feng wang <[email protected]<mailto:[email protected]>> wrote: Hello, I am using Slepc with a shell matrix. The sequential version seems working and now I am trying to make it run in parallel. The partition of the domain is done, I am not sure how to do the halo exchange in the shell matrix in Slepc. I have a parallel version of matrix-free GMRES in my code with Petsc. I was using VecCreateGhostBlock to create vector with ghost cells, and then used VecGhostUpdateBegin/End for the halo exchange in the shell matrix, would this be the same for Slepc? That will be enough for the MatMult(). You would also have to use a SLEPc EPS that only needed MatMult(). Thanks, Matt Thanks, Feng -- 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 https://www.cse.buffalo.edu/~knepley/<http://www.cse.buffalo.edu/~knepley/>
