# Coarse grid correction

#### Content

In general we would apply coarse grid corrections until a norm of the residual is below a given threshold (which depends on an error estimator). In this exercise we apply just a fixed number of iterations to see how the residual decreases.

## Exercise

Apply three iterations of the coarse grid correction:

• Plot the residual of the initial guess and

• the residual after each iteration.

• Plot the final approximate solution

Use a test case with exact solution $$u(x) = \sin{2 \pi e^{2x}}$$.