Parallelization in PUMA

• Implements implicit time integration schemes on distributed memory computers.
• Each compute node reads its own portion of the grid file at startup.
• Cells are divided among the active compute nodes at runtime based on cell ID (shown in figure) and only faces associated with local cells are read.
• Faces on the interface surface between adjacent computational domains are duplicated in both domains. Fluxes through these faces are computed in both domains.
• Solution variables are communicated between domains at every timestep which ensures that the computed solution is independent of the number of compute nodes.
• Communication of the solution across domains is all that is required for first-order spatial accuracy, since Q_L and Q_R are simply cell averages to the first order.
• If the left and right states are computed to higher-order, then Q_L and Q_R are shared explicitly with all adjacent domains. The fluxes through each face are then computed in each domain to obtain the residual for each local cell.