Hello, I ran the following KdV program, but the error between the numerical solution and the exact solution is not quite right. The program is as follows

DGKDV(n=1)07.27.edp (1.4 KB)

1dkdv mathematical model is as follows

The fully discrete format is as follows

first this code is wrong, remember freefem++ solve directly just linear system no no linear

so you have to use a algorithm to solve your no linear problem.

Sorry, I uploaded the wrong code. The following code corresponds to the above numerical format, but the error and convergence between the numerical solution and the exact solution have always been wrong.

KDV(n=1)07.27.edp (1.8 KB)