Many thanks, Dave! Best, Pham
On Sun, Oct 25, 2015 at 12:46 AM, Barry Smith <bsm...@mcs.anl.gov> wrote: > > > On Oct 24, 2015, at 1:43 AM, Sang pham van <pvsang...@gmail.com> wrote: > > > > Thank you, Dave, > > > > Can I just call My_DMCreateMatrix_DA_3d_MPIAIJ(DM da, Mat J, void* > my_context) when I need to create my matrix, and forget about > DMDASetGetMatrix()? > > You can do that if that is all you need. In some contexts when something > else in PETSc needs to create a specific matrix (like with geometric > multigrid) then that code calls DMCreateMatrix() which would then use your > creation routine. > > So, in summary you can start by just calling your own routine and > convert it to use DMSetGetMatrix() later if you need to. > > Barry > > > > > Thank you. > > > > Pham > > > > On Sat, Oct 24, 2015 at 1:33 PM, Dave May <dave.mayhe...@gmail.com> > wrote: > > If you need to access a user defined context from within your > CreateMatrix function, you can attach it to the DM via PetscObjectCompose > > > > > http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscObjectCompose.html > > > > If your context is not a petsc object, you can use > PetscContainerCreate(), > > > > > http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/Sys/PetscContainerCreate.html#PetscContainerCreate > > > > You would then set your user context pointer inside the container and > then use PetscObjectCompose() to attach the container to the DM > > > > Thanks, > > Dave > > > > > > On 24 October 2015 at 06:04, Sang pham van <pvsang...@gmail.com> wrote: > > Hi Barry, > > > > The routine DMCreateMatrix_DA_3d_MPIAIJ has 2 input arguments (DM da, > Mat J), the function pointer in DMDASetGetMatrix() only accept function > with that two arguments. > > As you suggested, I am writing a routine (based on > DMCreateMatrix_DA_3d_MPIAIJ()) to preallocate the matrix in the way I wish, > to do that I think It needs to have one more input argument: > My_DMCreateMatrix_DA_3d_MPIAIJ(DM da, Mat J, void* my_context). But > DMDASetGetMatrix() will not accept pointer of this function. Please give a > suggestion to overcome this. > > > > Thank you. > > > > Pham > > > > > > On Fri, Sep 4, 2015 at 1:24 AM, Barry Smith <bsm...@mcs.anl.gov> wrote: > > > > Look at DMCreateMatrix_DA_2d_MPIAIJ (or the 3d version if working > in 3d) You need to copy this routine and add whatever additional > preallocation information you need. Then call DMDASetGetMatrix() so that > the DM will use your routine to create the matrix for you. > > > > Barry > > > > > > > > > > > On Sep 3, 2015, at 11:28 AM, Sang pham van <pvsang...@gmail.com> > wrote: > > > > > > Hi, > > > > > > I am using DMCreateMatrix to create matrix from a existed DM object > and defined stencil. > > > In my code, boundary nodes need to involve many inner nodes, thus > matrix rows corresponding to boundary nodes are almost dense. How can I > tell petsc that those rows need to be preallocated with more entries? I > don't want to use MatMPIAIJSetPreallocation() since advantages of DM might > be lost. > > > > > > Many thanks. > > > > > > Sam. > > > > > > > > > > > > > > > >
