### Bug in createAIJ function ?

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-1

Hi,

I have a problem with setValuesCSR with a big model. The filling of the matrix is very very long whereas with numpy it is instantaneous. Therefore, i use the createAIJ function in order to filling my matrix. However i have a problem with this function. When i test these lines:

The first solution gives a bad result while the second gives good results. I would like to use the first solution so that I can use the basic functions of fenics (solve, ...). Could you help me ?

Thank you !

Best regards,

Arnaud

I have a problem with setValuesCSR with a big model. The filling of the matrix is very very long whereas with numpy it is instantaneous. Therefore, i use the createAIJ function in order to filling my matrix. However i have a problem with this function. When i test these lines:

```
A1=PETScMatrix()
A1.mat().createAIJ(size=(size_mat+size_groups, size_mat+size_groups), nnz=size_mat+size_groups*2 ,csr=(row_i,AValues[1],AValues[2]))
print A1.mat().getValuesCSR()
A1=PETScMatrix().mat().createAIJ(size=(size_mat+size_groups, size_mat+size_groups), nnz=size_mat+size_groups*2 ,csr=(row_i,AValues[1],AValues[2]))
print A1.getValuesCSR()
Results:
(array([0], dtype=int32), array([], dtype=int32), array([], dtype=float64))
(array([ 0, 9, 18, ..., 578061, 578061, 578061], dtype=int32), array([ 0, 264, 351, ..., 27828, 27829, 27830], dtype=int32), array([ 8.65384615, -1.92307692, -6.73076923, ..., -2.55443313,
-2.72414887, 13.38645699]))
```

The first solution gives a bad result while the second gives good results. I would like to use the first solution so that I can use the basic functions of fenics (solve, ...). Could you help me ?

Thank you !

Best regards,

Arnaud

Community: FEniCS Project

### 2 Answers

2

The first case is not supposed to work. You're using the petsc4py API wrong. It does not modify (already initialized!) matrix in place - rather it creates new.

For your use case. Create petsc4py matrix and then initialize DOLFIN PETScMatrix using existing the existing petsc4py object.

For your use case. Create petsc4py matrix and then initialize DOLFIN PETScMatrix using existing the existing petsc4py object.

1

thank you for your help! It works

```
A2=PETScMatrix().mat().createAIJ(size=(size_mat+size_groups, size_mat+size_groups),nnz=size_mat+size_groups*2 ,csr=(row_i,AValues[1],AValues[2]))
A1=PETScMatrix(A2)
print A1.mat().getValuesCSR()
```

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