From: Roy Stogner <roystgnr@ic...>  20090319 16:19:33

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 "arclength" procedure > for nonlinear structural problems. Check out John Peterson's dissertation. He did arclength continuation for some nonlinear fluid mechanics problems, and he contributed the physicsindpendent components of his code back to libMesh. You basically augment the nonlinear system with a single scalar arclength variable and solve an expanded problem with a weird (but still sparse!) operator structure.  Roy 