On Wed, Jun 10, 2020 at 9:08 AM Eda Oktay <eda.ok...@metu.edu.tr> wrote:
> Dear Matt, > > Matthew Knepley <knep...@gmail.com>, 10 Haz 2020 Çar, 16:03 tarihinde > şunu yazdı: > > > > On Wed, Jun 10, 2020 at 8:56 AM Eda Oktay <eda.ok...@metu.edu.tr> wrote: > >> > >> Hi all, > >> > >> I am trying to get all the rows of a parallel matrix as individual > >> vectors. For instance, if I have 72*4 matrix, I want to get 72 > >> different vectors having size 4. > >> > >> As far as I understood, MatGetRow is only for local rows, so > >> MatGetOwnershipRange is used, however, when I tried this one, I > >> couldn't get the whole and desired row vectors. > >> > >> In MatGetRow explanation, it is written that I should use > >> MatCreateSubMatrices first, then use MatGetRow. But I couldn't > >> understand to which extent I should create submatrices. I just need to > >> have all 72 rows as 72 different vectors each having 4 elements. > > > > > > 1) For sparse matrices, the storage is always divided by row, so that > values can only be retrieved for local rows with MatGetRow() > > > > 2) Is this matrix sparse? It sounds like it is dense. > > Matrix is dense. > > > > > 3) Are you asking to get all matrix values on all processes? If so, I > think the easiest thing to do is first wrap a Vec around the > > values, then use VecScatterToAll(), then wrap each one in a MatDense > again. > > Yes, I want all row vectors on all processes. In a dense matrix, > should I still wrap a Vec around the values? I know I should use > scatter but I couldn't even wrap a Vec around them. > I would do MatGetSize(&N); MatGetLocalSize(&m); https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatDenseGetArray.html <create vector of local size m*N> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecPlaceArray.html https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecScatterCreateToAll.html <do scatter> https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Vec/VecResetArray.html#VecResetArray https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Mat/MatCreateDense.html <use it> <destroy matrix> <destroy vector from CreateToAll> Thanks, Matt > Thanks so much! > > Eda > > > > > Thanks, > > > > Matt > > > >> > >> Thanks! > >> > >> Eda > > > > > > > > -- > > 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/ > -- 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/>
