Help: Serial code to parallel but even slower

Zonexo

Hi,

I've a serial 2D CFD code. As my grid size requirement increases, the simulation takes longer. Also, memory requirement becomes a problem. Grid size 've reached 1200x1200. Going higher is not possible due to memory problem.

Currently, I'm using the PETSc solver which is a parallel MPI solver, to solve the momentum and poisson eqn.

I tried to convert my code to a parallel one but after restructuring and enabling the parallel mode of the solver, I found that it is much slower, although the answer is correct.

I wonder what I should do to check what's wrong. Btw, is a grid size of 1200x1200 suitable for parallel run of 4 processors? I read that if grid is too small, it may be inefficient.

Thank you.