#include "petscconvest.h" PetscErrorCode PetscConvEstGetConvRate(PetscConvEst ce, PetscReal *alpha)Not collective
Note: The convergence rate alpha is defined by
|| u_h - u_exact || < C h^alphawhere u_h is the discrete solution, and h is a measure of the discretization size.
We solve a series of problems on refined meshes, calculate an error based upon the exact solution in the DS, and then fit the result to our model above using linear regression.