[MOAB-dev] Periodically flushing tags to disk?

[Tim Tautges]

I spent a lot of time thinking about that, and came to the following conclusions:

a) there were enough examples of file formats which duplicate the mesh for each time slice (actually, these look more 
like dumping a new file for each time) that taking that approach was not unique to MOAB; furthermore, there is 
tool-level support in paraview for reading time data as a series of individual files, including mesh in each file, such 
that a trivial amount of effort is required to implement a time-varying reader given a single-time reader.

b) in the in-memory database itself, it is unlikely that a code would choose to write a new tag for every timestep; 
rather, it would choose to have n different tags, for saving n timesteps worth of data, and cycle between them.

For those reasons, I eventually decided it wasn't a high enough priority to develop both individual-timestep/tag writing 
as well as time-dependent tags in MOAB.  I understood/stand that there would be a significant execution time advantage 
for doing that, but there always seemed to be bigger fish to fry (like getting an honest to goodness simulation code 
written based on MOAB).  Gerd, if you've gotten there now, maybe it is time to consider writing that kind of writer (and 
reader, since you'll also have to post-process the results of course).

- tim

On 07/02/2015 09:36 AM, Gerd Heber wrote:
> Happy 4th of July everybody!
>
> We are currently running a simulation, which creates new tags at runtime
> and only at the end writes the entire MOAB to disk (via DMMoabOutput).
> This method is wasteful and dangerous because we might run out of memory
> and, in case of premature termination, end up with nothing (on disk).
> We were wondering if there was a way to flush tags to disk periodically
> and limit our memory footprint? Ideally, this would not require writing
> the mesh again. We are also not wedded to the PETSc MOAB interface.
> If there is an MOAB-native way, that would be fine as well.
>
> Thanks, G.
>

-- 
Timothy J. Tautges
Manager, Directed Meshing, CD-adapco
Phone: (631) 629-3139 (internal: x29130)
Mobile/Gvoice: (608) 354-1459
timothy.tautges at cd-adapco.com