#include "petscksp.h" #include "petscmat.h" PetscErrorCode KSPConvergedRateView(KSP ksp, PetscViewer viewer)Collective on ksp
| ksp | - iterative context obtained from KSPCreate() | |
| viewer | - the viewer to display the reason |
| -ksp_converged_rate | - print reason for convergence or divergence and the convergence rate (or 0.0 for divergence) |
Suppose that the residual is reduced linearly, $r_k = c^k r_0$, which means $log r_k = log r_0 + k log c$. After linear regression, the slope is $\log c$. The coefficient of determination is given by $1 - \frac{\sum_i (y_i - f(x_i))^2}{\sum_i (y_i - \bar y)}$, see also https://en.wikipedia.org/wiki/Coefficient_of_determination