Re: [petsc-users] Question about preconditioner

On Thu, Feb 16, 2023 at 2:43 AM user_gong Kim wrote: > > > Hello, > > > > There are some questions about some preconditioners. > > The questions are from problem Au=b. The global matrix A has zero value > diagonal terms. > > 1. Which preconditioner is preferred for matrix A which has zero >

[petsc-users] Question for Petsc

Hello， I want to use Petsc to implement high performance computing, and I mainly want to apply DDM methods to parallel computing. I have implemented some of the DDM methods (such as ASM, Bjacobi, etc.), but I don't understand the PCBDDC method. The official example

Re: [petsc-users] Question about preconditioner

> On 16 Feb 2023, at 8:43 AM, user_gong Kim wrote: > >  > > > Hello, > > > > There are some questions about some preconditioners. > > The questions are from problem Au=b. The global matrix A has zero value > diagonal terms. > > 1. Which preconditioner is preferred for matrix A

Re: [petsc-users] Question for Petsc

On Thu, Feb 16, 2023 at 9:14 AM ziming xiong wrote: > Hello， > I want to use Petsc to implement high performance computing, and I mainly > want to apply DDM methods to parallel computing. I have implemented some of > the DDM methods (such as ASM, Bjacobi, etc.), but I don't understand the >

Re: [petsc-users] dmplex overlap questions

On Feb 16, 2023, at 10:54 AM, Lawrence Mitchell wrote: Hi Blaise, On Thu, 16 Feb 2023 at 15:17, Blaise Bourdin wrote: Hi, I am trying to implement a non-local finite elements reconstruction operator in parallel. Given a dmplex distributed with an overlap, is there a

Re: [petsc-users] Question for Petsc

For bddc, you can also take a look at https://gitlab.com/petsc/petsc/-/blob/main/src/ksp/ksp/tutorials/ex71.c On Thu, Feb 16, 2023, 19:41 Matthew Knepley wrote: > On Thu, Feb 16, 2023 at 9:14 AM ziming xiong > wrote: > >> Hello， >> I want to use Petsc to implement high performance computing,

Re: [petsc-users] Question about preconditioner

If your matrix has the form ( A B ) ( C 0 ) then often PCFIELDSPLIT can be a useful preconditioner with the option -pc_fieldsplit_detect_saddle_point > On Feb 16, 2023, at 2:42 AM, user_gong Kim wrote: > > > Hello, > > > There are some questions about some

Re: [petsc-users] dmplex overlap questions

On Thu, Feb 16, 2023 at 10:54 AM Lawrence Mitchell wrote: > Hi Blaise, > > On Thu, 16 Feb 2023 at 15:17, Blaise Bourdin wrote: > > > > Hi, > > > > I am trying to implement a non-local finite elements reconstruction > operator in parallel. > > > > Given a dmplex distributed with an overlap, is

Re: [petsc-users] dmplex overlap questions

On Thu, 16 Feb 2023 at 16:43, Matthew Knepley wrote: > > On Thu, Feb 16, 2023 at 10:54 AM Lawrence Mitchell wrote: >> >> Hi Blaise, >> >> On Thu, 16 Feb 2023 at 15:17, Blaise Bourdin wrote: >> > >> > Hi, >> > >> > I am trying to implement a non-local finite elements reconstruction >> >

[petsc-users] dmplex overlap questions

Hi, I am trying to implement a non-local finite elements reconstruction operator in parallel. Given a dmplex distributed with an overlap, is there a way to figure out which cells are in the overlap and which are not? Alternatively, suppose that I distribute the same DM with and without an

Re: [petsc-users] dmplex overlap questions

Hi Blaise, On Thu, 16 Feb 2023 at 15:17, Blaise Bourdin wrote: > > Hi, > > I am trying to implement a non-local finite elements reconstruction operator > in parallel. > > Given a dmplex distributed with an overlap, is there a way to figure out > which cells are in the overlap and which are

Re: [petsc-users] dmplex overlap questions

On Thu, Feb 16, 2023 at 1:09 PM Lawrence Mitchell wrote: > On Thu, 16 Feb 2023 at 16:43, Matthew Knepley wrote: > > > > On Thu, Feb 16, 2023 at 10:54 AM Lawrence Mitchell wrote: > >> > >> Hi Blaise, > >> > >> On Thu, 16 Feb 2023 at 15:17, Blaise Bourdin > wrote: > >> > > >> > Hi, > >> > > >>

Re: [petsc-users] PetscViewer with 64bit

Jed, It does not work for me even with the reproducer case with the small 2D square mesh. Can you run the case that I sent and open the created "sol.vtu" file with paraview? Thanks, > Thanks, Dave. > > Mike, can you test that this branch works with your large problems? I > tested that .vtu

Re: [petsc-users] PetscViewer with 64bit

Thanks, Dave. Mike, can you test that this branch works with your large problems? I tested that .vtu works in parallel for small problems, where works = loads correctly in Paraview and VisIt. https://gitlab.com/petsc/petsc/-/merge_requests/6081 Dave May writes: > On Tue 14. Feb 2023 at

Re: [petsc-users] PetscViewer with 64bit

Okay, this works now. I'm pretty sure I tested this long ago with connectivity using Int64 and found that didn't work. That may have been ancient history, but I'm hesitant to revamp to match PetscInt. If doing that, it would require changing the signature of DMPlexGetVTKConnectivity to use

[petsc-users] Question about rank of matrix

Hello, I have a question about rank of matrix. At the problem Au = b, In my case, sometimes global matrix A is not full rank. In this case, the global matrix A is more likely to be singular, and if it becomes singular, the problem cannot be solved even in the case of the direct solver. I haven't

Re: [petsc-users] Question about rank of matrix

On Fri, Feb 17, 2023, 10:43 user_gong Kim wrote: > Hello, > > I have a question about rank of matrix. > At the problem > Au = b, > > In my case, sometimes global matrix A is not full rank. > In this case, the global matrix A is more likely to be singular, and if it > becomes singular, the