Dear Prof. Pierre Jolivet,
Your know, after solving a PDE for u, we can use dx(u) to get the derivative of u.
However, In the case parallel, it seems we cannot directly do so, because I found the results were different between using one processor and two processors.
Do we have to gather (centralise) u to one processor, compute the derivative, and then distribute the results across different processors? or there is a simple trick?
Best,
Yongxing.