From: John Peterson <peterson@cf...>  20090319 16:16:51

On Thu, Mar 19, 2009 at 11:07 AM, Vasilis Vavourakis <vasvav@...> wrote: > i don't know if this might sound a silly question BUT i want to > perform the inversion of a "DenseMatrix" of a system... > > to be more specific, i want to implement the "arclength" procedure > for nonlinear structural problems. > for this topic see: Crisfield M.A.  NonLinear Finite Element > Analysis of Solids and Structures Vol. 1 (see pages: 266286) > one of the solutions proposed in the book is to invert the "tangent > stiffness matrix" (the Jacobian matrix in other words) Yes, this is a standard technique but the Jacobian is not dense if you are using a standard finite element discretization. Usually it is "bordered" which means there is one dense row and column augmenting the original system.  John 