First of all thank you everybody for the fast replies. Barry, I think the solution 1 is a good suggestion but I confess I’m a bit scared of going deep into the modification of the ODE integrator. I’m now using TSCN, the classical Crank-Nicolson 2nd order full implicit time integration. Maybe I can try to implement your solution together with BEULER, as suggested by Hong. By the way the solution changes rapidly, but not so fast to justify that small timestep value. The space variation instead are really fast and this is the reason why I need so many grid points.
Jed, I hope you could solve soon the problem with the FAS scheme. Thank you again Francesco
