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[Anders Logg <question127219@xxxxxxxxxxxxxxxxxxxxx>]

Question #127219 on DOLFIN changed:
https://answers.launchpad.net/dolfin/+question/127219

    Status: Open => Answered

Anders Logg proposed the following answer:
On Tue, Sep 28, 2010 at 09:12:47PM -0000, cutejeff wrote:
> New question #127219 on DOLFIN:
> https://answers.launchpad.net/dolfin/+question/127219
>
> I have been doing the mesh refinement convergence study.  The simulations worked very well for meshes Rectangle(0,0,5,5,50,50) and Rectangle(0,0,5,5,50,100). But if I use a finer mesh Rectangle(0,0,5,5,100,100), it caused the "out of memory" error.
>
>  I have 10G memory on my computer and I looked at the hardinfo, I still have about 5-6g memory left when Fenics was running. So I guess there are some limitations on memory allocation in Fenics. Is there a way to allocate more memory for Fenics?
>
> What should I do in my case? Because I have a high order equation(4th), and it's kind of complicated, I split it into 4 mixed equations. Therefore, it requires V*V*V*V function spaces and makes the linear system size (161604 x 161604) much bigger than a single equation.
>
> I am considering to make less mixed equations. But I don't know how to do it. Isn't mixed-equations the only way for high order PDE?
> For example in 1D case, du/dt+ d/dx(u+u''')=0, what all I know to do this is that, split it into 3 equations
> du/dt+dT=0
> T=u+dK/dx
> K=u''
>
> Then I can make weak form for equation3, and it works. But I have to have 3 mixed equations. Is this the only way to do it? I couldn't find any examples in demos.
>
> Any suggestions would help a lot. Thank you.

Do you have a 64bit operating system? Otherwise, I expect you will not
be able to allocate more than 4GB with any single program.

--
Anders

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