Hi, I am trying to run 3D simulations in parallel with 1D homogeneous in the span-wise direction. For a certain number of Fourier Modes the simulation runs smoothly, but increasing them beyond some critical value causes an error to pop up, and this error is not related to memory shortage. The cluster in which simulation is being run has the capacity of running 192 processors with 2GB Ram/core in parallel environment. Just to give you an idea, in my case with homogeneous modes 64 things are perfect and increasing them causes simulation to crash giving errors like: Fatal : Level 0 assertion violation Exceeded maximum number of iterations srun: error: s02r2b71: tasks 0-47: Exited with exit code 1 CG iterations made = 5001 using tolerance of 1e-09 (error = -nan, rhs_mag = 1) I would appreciate if someone could suggest something. Best Regards