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[cutejeff <question127219@xxxxxxxxxxxxxxxxxxxxx>]

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.

 

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