why mod(re.float()).item() + U_groundtruth(re) ?

[929140226]

I dont understand why add U_groundtruth(re) in draw_graph(mod,m) and many other functions, does it means that you get the truth solution at mod==0?

[ZeyuJia]

Actually we calculate the solution -u instead of u in my implementation (you can check the PDE's variational form by yourself). I am sorry I didn't make it clear before.