[petsc-users] huge sparse structured block matrix

[Matthew Knepley]

On Thu, Oct 3, 2013 at 8:04 AM, mary sweat <mary.sweat78 at yahoo.it> wrote:

> Hi all
> I am very new to petsc and to c programming. I need to build a huge sparse
> matrix with a block structure.
> The problem is that my matrx may be huge (200000*200000) so i Need a way
> to define it through the kronecker product or memorizing just the
> overdiagonal, diagonal and subdiagonal block.
> Is it possible in petsc? any suggestions?
> thanks a million in advance
>

This is the 2D Laplacian with a 5-point FD stencil. There are many PETSc
examples which
form and solve this. For example, here is an example:

  1,640,961 unknowns (on the fine level)

  8,199,681 nonzeros

  ./ex5 -da_grid_x 21 -da_grid_y 21 -da_refine 6 -ksp_rtol 1.0e-9 -pc_type
mg -pc_mg_levels 4 -snes_monitor -snes_view

This takes 375s on my underpowered Mac Air laptop.

  Thanks,

     Matt

-- 
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
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