# integrating Poisson Equation solution over its domain

Asked by
Payman Tohidifar
on 2013-02-13

Dear all,

I was wondering if I can compute integral of the solution for Poisson equation over an arbitrary domain. Dolfin is able to compute derivatives at each point by defining a vector function space but I don't know how to compute integral of solution function over the domain. I would be thankful if you help me out.

## Question information

- Language:
- English Edit question

- Status:
- Solved

- For:
- DOLFIN Edit question

- Assignee:
- No assignee Edit question

- Solved by:
- Marie Rognes

- Solved:
- 2013-02-13

- Last query:
- 2013-02-13

- Last reply:
- 2013-02-13

Christian Waluga (chris-1) said : | #1 |

Try assemble(uh*dx), where uh is your solution. Is that what you want?

Marie Rognes (meg-simula) said : | #2 |

If u is your solution, try

M = assemble(u*dx)

M is then the value of the integral of the solution over the mesh.

Payman Tohidifar (payman-che) said : | #3 |

Thank you very much guys. It worked pretty well.

Payman Tohidifar (payman-che) said : | #4 |

Thanks Marie Rognes, that solved my question.

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