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[Johan Hake <question129481@xxxxxxxxxxxxxxxxxxxxx>]

Question #129481 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/129481

    Status: Open => Answered

Johan Hake proposed the following answer:
On Thursday October 14 2010 12:20:55 Andy R Terrel wrote:
> New question #129481 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/129481
> 
> I need to write out some assembled matrices in Matrix Market format,
> hopefully from the Python interface.  Easily for small matrices I can do:
> 
> from dolfin import *
> from scipy.io import mmio
> from scipy.sparse import csr_matrix
> ...
>        A = Matrix()
>         b = Vector()
> 
>         assemble_system(a, L, bcs=bc0, A_tensor=A, b_tensor=b)
> 
>         mmio.mmwrite("A.mtx", csr_matrix(A.array()))
>         mmio.mmwrite("b.mtx", csr_matrix(b.array()))
> 
> But once A gets large calling "A.array()" takes forever.  Is there a way in
> python that I can just query the sparsity structure of A?
> 
> Any other ideas on how to do this quickly?

Shift backend to MTL4 or uBLAS and then:

   rows, cols, values = A.data()

Johan

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