From: Dafang Wang <dafang.wang@jh...>  20131215 05:57:47

Hi, My question concerns repeated solving a nonlinear system for multiple times. I am trying to fit some input parameters for an inherently unstable nonlinear implicit system. Fewer than 5 parameters need fitting, so it is a small parameterfitting problem. To fulfill this goal, I am solving the nonlinear system repeatedly as follows: NonlinearImplicitSystem system; Initialize the input parameters to the object "system"; Repeat Update the input parameters to "system"; (The update does NOT depend on the system's current solution.) system.solve(); Until system.solution() meets the defined goal Here is my problem: because the system is by nature unstable, system.solve() sometimes did not converge; then in the next round of solve, I obtained a very odd solution even though system.solve() converged well. My question is whether a failed nonlinear solve will leave some bad intermediate values in the NonlinearSystem object and thereby influence its next solve? For example, I think that the system.solution will be used as the initial guess in the next solve; then will a partial solution be bad enough to crash the system? In my problem, the input parameters were updated independently from system.solution. Also my update change was small, thus unlikely responsible for the failure of the next solve. The remaining uncertainty is the NonlinearSystem's partial solution or its internal state variables. Any comments will be greatly appreciated. Best, Dafang  Dafang Wang, Ph.D. Postdoctoral Fellow Institute of Computational Medicine Hackerman Hall, Room 218 Johns Hopkins University, Baltimore, 21218 http://lagniappe.icm.jhu.edu/~dwang/ 