## [Libmesh-users] Accumulated solution

 [Libmesh-users] Accumulated solution From: Roy Stogner - 2006-03-27 15:01:45 ```On Sun, 26 Mar 2006, li pan wrote: > maybe it's a little stupid. But I have to say it. In > the Netwon iteration code of ex13, I can't find > something like Xn+1 = Xn + deltaX. Oh! I completely misunderstood what you meant by "accumulated solution". This isn't a stupid question at all, because different codes do it in different ways. In example 13, I believe what's going on is that the solution vector itself, *stokes_system.solution, is being used to hold Xn+1. I think I've just about convinced John that for more tricky nonlinear problems it's better for the system solution to hold the difference between deltaX at the last Newton step and deltaX at the current Newton step, though; the equations usually come out simpler, and it ends up being easier to program quasiNewton schemes and convergence tests. John, Ben, am I right about ex13? We probably ought to add comments to the nonlinear loop explaining as much. --- Roy Stogner ```

 [Libmesh-users] Accumulated solution From: Roy Stogner - 2006-03-27 15:01:45 ```On Sun, 26 Mar 2006, li pan wrote: > maybe it's a little stupid. But I have to say it. In > the Netwon iteration code of ex13, I can't find > something like Xn+1 = Xn + deltaX. Oh! I completely misunderstood what you meant by "accumulated solution". This isn't a stupid question at all, because different codes do it in different ways. In example 13, I believe what's going on is that the solution vector itself, *stokes_system.solution, is being used to hold Xn+1. I think I've just about convinced John that for more tricky nonlinear problems it's better for the system solution to hold the difference between deltaX at the last Newton step and deltaX at the current Newton step, though; the equations usually come out simpler, and it ends up being easier to program quasiNewton schemes and convergence tests. John, Ben, am I right about ex13? We probably ought to add comments to the nonlinear loop explaining as much. --- Roy Stogner ```