John you are right, the matrix is not DENSE, it's banded ;) i just typed the class of matrix i declared in my assembly function!
2009/3/19 Roy Stogner <[email protected]>: > > On Thu, 19 Mar 2009, Vasilis Vavourakis 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... > > There's a reason why the Matlab "inv" help page begins: "In practice, > it is seldom necessary to form the explicit inverse of a matrix" - and > that's talking with dense matrices in mind! For large sparse matrices > inversion is usually much, much less efficient than iterative solves. > >> to be more specific, i want to implement the "arc-length" procedure >> for non-linear structural problems. > > Check out John Peterson's dissertation. He did arc-length > continuation for some nonlinear fluid mechanics problems, and he > contributed the physics-indpendent components of his code back to > libMesh. You basically augment the nonlinear system with a single > scalar arc-length variable and solve an expanded problem with a weird > (but still sparse!) operator structure. Roy, you are right too, the simplest way to implement the arc-length procedure is to augment the system with one "constraint" equation... the problem is that it's not that clear to me (i'm not that a libmesh expert) to add another "one" degree-of-freedom in the system! however i'll try to have a look at John dissertation :) although Crisfield's book seems to be very clarifying to that issue. many thanks again for the prompt replies > --- > Roy > ------------------------------------------------------------------------------ Apps built with the Adobe(R) Flex(R) framework and Flex Builder(TM) are powering Web 2.0 with engaging, cross-platform capabilities. Quickly and easily build your RIAs with Flex Builder, the Eclipse(TM)based development software that enables intelligent coding and step-through debugging. Download the free 60 day trial. http://p.sf.net/sfu/www-adobe-com _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
