Dear Wen,
You are right that from a purely mathematical view, there is a bias estimating the error as it is done in elastostatic example. However, most of the time, the two errors are of the same order. For the moment, there is only one way to compute the error by accounting of the value of the exact solution in each Gauss point. This way is to use a mesh_fem_global_function defined in getfem_mesh_fem_global_function.h. It defines a mesh_fem structure having a certain number of degrees of freedom globally defined on the mesh and represented by some global functions which will be interpolated on each Gauss point. It is used for instance in crack.cc and in particular allows to estimate the error with the exact solution. I also plane to accept user defined function directly in generic assembly but it is still a work in progress. Yves. ----- Original Message ----- From: "Wen Jiang" <[email protected]> To: [email protected] Sent: Friday, November 1, 2013 4:34:26 PM Subject: [Getfem-users] elastostatic example error evaluation Hi, I am testing the elastostatic example in the test folder. I have a question about the error evaluation (L2 and H1). The way how the error is evaluated in the code is firstly to get the error only at the node and then to interpolate the node error and assemble. I do not think this is the general way that the error should be evaluated since the exact solution cannot be interpolated by the shape function for general cases. In the code, the l2 and h1 errors are just machine error when only 1by1 element is used. And this is because the error at the node is zero and the error interpolated within element is identical zero. Thus, I am wondering whether getfem++ provide any other method to calculate the errors in a better way, meaning that the exact solution is evaluated at each gaussian point instead of interpolating by the node value. Also I would like to know that whether the energy norm for elasticity problem has been implemented yet. Thanks in advance. Regards, Wen _______________________________________________ Getfem-users mailing list [email protected] https://mail.gna.org/listinfo/getfem-users _______________________________________________ Getfem-users mailing list [email protected] https://mail.gna.org/listinfo/getfem-users
