[petsc-users] matrix memory preallocation

[Sun, Hui]

Dear Petsc users,

I have a DM object by claiming
DMDACreate3d(PETSC_COMM_WORLD,DMDA_BOUNDARY_NONE,DMDA_BOUNDARY_NONE,DMDA_BOUNDARY_NONE,DMDA_STENCIL_BOX,32,32,32,PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE,3,5,0,0,0,&da);

There is a problem with it, because it uses DMDA_STENCIL_BOX, and the stencil width is 5, quite big.

However, in fact, I don't need such big stencils everywhere, I only need it at a sparse number of locations. I'm wondering how to allocate memory only in those sparse number of locations?

Thank you very much!

Best,
Hui
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