Garth N. Wells wrote: > On Aug 23 2007, Jake Ostien wrote: > >> Hi, >> >> I am trying to compute some reaction forces, currently I am trying to >> assemble the stiffness matrix and compute the matrix vector product >> with the converged solution vector to get a vector of forces. Here >> is what I am trying. >> >> <u is the converged solution> >> Matrix A; >> assemble(A, *a, mesh); >> Vector f; >> A.mat().mult(u.vector().vec(), f.vec()); >> >> First an issue. I am getting a seg fault coming in >> DiscreteFunction::interpolate as part of the assemble step. I >> haven't figured out why yet, but I'm looking. >> >> Next, a few questions. >> Is there an easier (or cleaner) way to accomplish this? >> > > Yes, you should be able to assemble a linear form which will contain > the reaction forces. For elasticity, plasticity, etc > > L = -grad(v)*sigma*dx - v*f*dx (f is the body force) > > Assemble this into a vector, and the vector will contain the reaction > forces. Yes, thanks, this works great. (Sorry for the duplicate Garth, I forgot to copy the mailing list). Jake > > Garth > >> I have a mixed formulation. Is is possible to only assemble the >> stiffness matrix for a SubSystem? >> Thanks, >> Jake >> >> _______________________________________________ >> DOLFIN-dev mailing list >> [email protected] >> http://www.fenics.org/mailman/listinfo/dolfin-dev >> > >
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