On 4 September 2010 15:32, Dominique <question123...@answers.launchpad.net> wrote: > Question #123984 on DOLFIN changed: > https://answers.launchpad.net/dolfin/+question/123984 > > Status: Answered => Open > > Dominique is still having a problem: > Johan, > > Thanks for the pointer. I had looked at the hyperelasticity demo. I > should have called my post "Second derivatives of a weak form". In the > hyperelasticity demo, the weak form is L(v,u)=0 and that is only > differentiated once. What I'd like to do is differentiate the result > once more. If I try > > d2u = TrialFunction(V)
Test- and TrialFunction are just helper functions for pretty syntax. They will both return an instance of the class ufl.Argument, the TestFunction with count = -2, TrialFunction with count = -1, when you take the derivative w.r.t. yet another TrialFunction in your form I suspect you end up with something TrialFunction*TrialFunction which is not a linear in each basis function argument. So I think you need to use Argument(element, 0), or something to get your rank 3 tensor. Kristian > da = derivative(a, u, d2u) > print assemble(da, mesh=mesh) > > in the hyperelasticity demo, I get the same error as in my initial > message. > > In my test example above, a(v,u)=0 is a weak form. Differentiating it > once is OK, but what is the trick to compute second derivatives? > > If I'm missing your point, I'm sorry but could you please explain what > is wrong in my example? I'm expecting to obtain a tensor of order 3, or > a collection of matrices. I may not be going about it in the right way. > > Thanks! > Dominique > > -- > You received this question notification because you are a member of > DOLFIN Team, which is an answer contact for DOLFIN. > > _______________________________________________ > Mailing list: https://launchpad.net/~dolfin > Post to : dolfin@lists.launchpad.net > Unsubscribe : https://launchpad.net/~dolfin > More help : https://help.launchpad.net/ListHelp > _______________________________________________ Mailing list: https://launchpad.net/~dolfin Post to : dolfin@lists.launchpad.net Unsubscribe : https://launchpad.net/~dolfin More help : https://help.launchpad.net/ListHelp
