Hey David, On Tue, Mar 29, 2016 at 10:43 PM, David Knezevic <[email protected] > wrote:
> I'm using FEMSystem for a problem, and I'm getting solid quadratic > convergence with the Newton solver. However, when I turn on the finite > difference jacobian check using "verify_analytic_jacobians = 1.e-6" it > reports an error: > "Relative error 0.133922 detected in analytic jacobian on element 0!" > There are circumstances where I get this behavior, that is quadratic convergence and the Jacobian is (partially) wrong. The one that pops to mind is my Rayleigh-damping implementation, where I haven't yet implemented parts of the Jacobian. (Just to satisfy any curiosity, for material nonlinearities, C(i,j,k,l) has non-zero derivatives w.r.t. strain, so I haven't yet gone to the trouble to implement them, but I have the Jacobian for all the other parts.) > I expected the code to pass this test, given that I'm getting good > convergence behavior. So before I do too much more bug-hunting, I just > wanted to check if there's a chance that I might be getting a "false > positive" with the finite difference jacobian check? > I have yet to find a case where I got a false positive. I find it helpful to get to a very small problem and compare the elements to zone in on the terms that differ. HTH, Paul ------------------------------------------------------------------------------ Transform Data into Opportunity. Accelerate data analysis in your applications with Intel Data Analytics Acceleration Library. Click to learn more. http://pubads.g.doubleclick.net/gampad/clk?id=278785471&iu=/4140 _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
