FullMatrix direct solver

[Joss G.]

Good afternoon, 

I have a basic question. I can see that for sparse matrix the function SparseDirectUMFPACK.vmult() solves Ax=b. I am trying now to solve  a system with full matrix. I can see that the function FullMatrix.vmult() does not apply the inverse as in the sparse analogy. What is the best way in Deal.ii to solve Ax=b with fullmatrix using a direct solver approach?

Thank you

[Bruno Turcksin]

Hello,

You can use the invert function to get the inverse of the matrix and then you can use vmult with the new matrix.

Best,

Bruno

[Joss G.]

Good afternoon,

Thank you for your answer.

When using the function invert, I get sometimes the following running error:

An error occurred in line <1849> of file </zhome/32/9/115503/dealii-candi/tmp/unpack/deal.II-v9.3.1/include/deal.II/lac/full_matrix.templates.h> in function

    void dealii::FullMatrix<number>::gauss_jordan() [with number = double]

The violated condition was: 

    info == 0

Additional information: 

    (none)

I am not sure what is happening, as the matrix is invertible. Sometimes after compiling few times and run, it works.

Could you please help me understand what the problem could be?

Thank you

Regards, 

[Bruno Turcksin]

Hello,

Could you print the value of info (you can use gdb to do that). That
would help us understand what's the problem.

Best,

Bruno

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