1. An Advanced Simulation & Computing (ASC) Academic Strategic Alliances Program (ASAP) Center at The University of Chicago The Center for Astrophysical Thermonuclear Flashes IO Architecture Notes

2. The ASC/Alliances Center for Astrophysical Thermonuclear Flashes The University of Chicago IO Scalar Quantities  Information that is needed for the simulation that is neither grid data, nor defined as a runtime parameter (ie. simulation time)  Each unit writes what, if any, scalar values they own through sendOutputScalars, which is called by IO.  Output scalars are read back during IO_init in Driver_initFlash

3. The ASC/Alliances Center for Astrophysical Thermonuclear Flashes The University of Chicago Integral Quantities  Quantities are integrated by volume over the grid.  Cartesian geometries are supported by default as well as 2D Cylindrical.  Frequently overridden to provide additional functionality  Does not utilize any of the IO unit’s output machinery, you are responsible for your own MPI communication if you override the file.  Recommended that you use Flash_mpi.h and FLASH_REAL for MPI calls.

4. The ASC/Alliances Center for Astrophysical Thermonuclear Flashes The University of Chicago IO Caveats and Gotchas  IO has a few exceptions to our general architecture rules  Can directly access the Grid unit’s data  Not all of IO is included by default  IOMain and IOParticles are separate subunits!  Restarts do interact with the environment  Runtime parameters from the Config files and flash.par trump values stored in a checkpoint  Values for Runtime Parameters in checkpoints are stored as a previous value  Initialization Order  IO_init must be called before any scalar quantities are used  This includes sim_time!  Logfiles are their own unit. They are not a part of the IO unit  Diagnostic IO: watch who is writing to what file

5. The ASC/Alliances Center for Astrophysical Thermonuclear Flashes The University of Chicago IO and Grid Variables  The reading and writing of Grid variables are handled differently depending on type.  Unknowns are both written and read by default  Only variables to be plotted, at this time  Face-centered data will be checkpointed if declared  Fluxes are not checkpointed at all  Scratch variables may be checkpointed for diagnostic purposes, but are never read back in