Dear Nektar++ -Community, please can you tell me the default operator evaluation in Nektar++? In the papers "From h to p efficiently" there are mentioned three kind of types: 1. global matrix approach 2. local matrix approach 3. sum-factorization I want to choose the best hp/ configuration for my 3D simulation and this -of course- depends on the operator evaluation strategy. I think actually Nektar++ uses the global matrix approach by default, but I'm not sure by 100%. My second question depends on the error message: "Fatal : Level 0 assertion violation NaN found during time integration." While using this configuration: ======================================================================= EquationType: EulerCFE Session Name: 3Dmeshcube_h10 Spatial Dim.: 3 Max SEM Exp. Order: 3 Num. Processes: 24 Expansion Dim.: 3 Riemann Solver: HLLC Advection Type: Projection Type: Discontinuous Galerkin Diffusion Type: Advection: explicit AdvectionType: WeakDG Diffusion: explicit Time Step: 0.01 No. of Steps: 10000 Checkpoints (steps): 1000 Integration Type: RungeKutta2_ImprovedEuler Problem Type: General ======================================================================= Initial Conditions: - Field rho: rhoInf + (0.01 * exp(-0.077*(x^2 + y^2 + z^2))) - Field rhou: rhoInf * uInf - Field rhov: rhoInf * vInf - Field rhow: rhoInf * wInf - Field E: (pInf / (Gamma - 1)) + ((rhoInf/2) * uInf^2) + ((0.01/(Gamma-1))*exp(-0.077*(x^2 + y^2 + z^2))) +( (0.01/2) * uInf^2 * exp(-0.077*(x^2 + y^2 + z^2))) I already changed my time-step and the refinement of my mesh and i think this error message is because of oscillation of my solution. So maybe my mesh is not fine enough or i must increase p. But i want to use a fix h to p constellation to test the efficiency. Can anybody help me with this problem? I already tried to use the spectral hp dealiasing, the smooth advection and artificial viscosity, but it doesn't worked or helped... Thanks for any answer. Best regards Fabian