The calculation advances in time for all zones until the solution has converged to the user's satisfaction. Typical problem sizes range from small calculations involving about one million points to simulations of an entire aircraft requiring tens of millions of points. On the CRAY C90, the standard solution approach is to sequentially process each 3D zone through one timestep. Once all zones have been advanced to the new time, the process repeats and all zones are advanced to the next time level.
Typical solutions require thousands of timesteps to reach convergence.
Typical microtasking parallel efficiency for the code is about 11 of 16 CPUs when the C90 is in dedicated mode. For example, the code has also been converted to solve the flow field in a more coarsely parallel fashion using MPI, the Message Passing Interface. The MPI approach is theoretically more efficient than the standard C90 code in that it attempts to parcel the zones to different processors in such a way that many zones are being processed simultaneously at each timestep. One drawback to the MPI approach is that it is subject to the latencies and added overhead imposed by MPI's message passing library. This library of messaging subroutines is used to communicate boundary values and other data between the zones as the solution progresses.