[petsc-users] Get global column indices thay belong to another process?

Assuming you preallocate/assemble a MPIAIJ matrix “by hand” using a ISLocalToGlobalMapping object obtained from DMDA: what’s the easiest way to get global column indices that do not belong to a process? Say, if you have a finite-difference stencil and the stencil exceeds the portion owned by

Re: [petsc-users] About DMDA (and extracting its ordering)

Hi Matthew, I’ve just attached on that page https://bitbucket.org/petsc/petsc/issues/262 the same source code written in C that runs just fine from what I can see. Which means there’s either a bug in ISLocalToGlobalMappingGetIndicesF90 or something missing in the documentation. Best, Thibaut

Re: [petsc-users] About DMDA (and extracting its ordering)

Hi Matthew, Yes I need F90 and the syntax in the file / yours PetscInt, pointer :: id_ltog(:) Is the exact same as PetscInt, dimension(:), pointer :: id_ltog They’re both modern fortran ”correct” Anyways I tried both and I still get the same error message. Thibaut On 24 Feb 2019, at 23:38,

Re: [petsc-users] About DMDA (and extracting its ordering)

Is that for the id_ltog argument? I tried declaring it as IS, and you can’t declare an deferred-shape array as target. Same message. XXX(:) is syntactic sugar for dimension(:) :: XXX I’m really confused because this

Re: [petsc-users] About DMDA (and extracting its ordering)

Hi Matthew, With the following data declaration and routines calls: DM :: da ISLocalToGlobalMapping :: ltog PetscInt, DIMENSION(:), POINTER :: id_ltog CALL DMDACreate2D(PETSC_COMM_WORLD,DM_BOUNDARY_NONE,DM_BOUNDARY_NONE,DMDA_STENCIL_STAR,(nx+1),(ny+1), &

Re: [petsc-users] About DMDA (and extracting its ordering)

Hi Matthew, I think I need the whole G2L not just the sizes. Build my own matrix, create a “fake” DMDA, extract the G2L mapping and apply it to my preallocation/assembly routines (where I would basically replace my natural ordering with the DMDA ordering from the G2L mapping) (cf the mail I

Re: [petsc-users] On unknown ordering

Hi Barry, > Le 15 nov. 2018 à 18:16, Smith, Barry F. a écrit : > > > >> On Nov 15, 2018, at 4:48 AM, Appel, Thibaut via petsc-users >> wrote: >> >> Good morning, >> >> I would like to ask about the importance of the initial choice of

[petsc-users] On unknown ordering

Good morning, I would like to ask about the importance of the initial choice of ordering the unknowns when feeding a matrix to PETSc. I have a regular grid, using high-order finite differences and I simply divide rows of the matrix with PetscSplitOwnership using vertex major, natural

Re: [petsc-users] DIVERGED_NANORING with PC GAMG

maximum iterations=1, initial guess is zero >> tolerances: relative=1e-05, absolute=1e-50, divergence=1. >> left preconditioning >> using DEFAULT norm type for convergence test >> PC Object: (fieldsplit_2_) 1 MPI processes >> type not yet set >&

Re: [petsc-users] DIVERGED_NANORING with PC GAMG

e: > On Oct 31, 2018, at 5:39 PM, Appel, Thibaut via petsc-users > mailto:petsc-users@mcs.anl.gov>> wrote: > > Well yes naturally for the residual but adding -ksp_true_residual just gives > > 0 KSP unpreconditioned resid norm 3.583290589961e+00 true resid norm > 3.5

Re: [petsc-users] DIVERGED_NANORING with PC GAMG

t you meant? If you could let me know what should be corrected. Thanks for your support, Thibaut On 31/10/2018 16:43, Mark Adams wrote: On Tue, Oct 30, 2018 at 5:23 PM Appel, Thibaut via petsc-users wrote: Dear users, Following a suggestion from Matthew Knepley I’ve been trying to a

[petsc-users] DIVERGED_NANORING with PC GAMG

Dear users, Following a suggestion from Matthew Knepley I’ve been trying to apply fieldsplit/gamg for my set of PDEs but I’m still encountering issues despite various tests. pc_gamg simply won’t start. Note that direct solvers always yield the correct, physical result. Removing the fieldsplit