Extend data structure for TallyData

[kldunn]

DAGMC tallies currently store their data as three std::vector objects:

• tally_data: total sum of scores
• error_data: total sum of squares of scores
• temp_tally_data: sum of scores for one history

The size of each of these vectors is the number of tally points multiplied by the number of energy bins. This limits the maximum size of the tallies that can be defined. It may be worth looking into an alternative, more multidimensional data structure. This data structure could also allow for future expansion - such as adding time or angle binning, or allowing for more than one tally multiplier per tally.

[makeclean]

@kldunn, quick question why would reshaping this data reduce memory usage? Or am I missing something?

[kldunn]

It wouldn't reduce memory usage. However, it would give you more flexibility with how many multipliers and tally points can be added to a single tally definition. The way it is set up right now, each of these vectors will have a size of tally points * number of energy bins. If you start to add in more than one multiplier with many energy bins per tally these vectors could potentially reach the maximum size of a vector for really large meshes. At this point it is probably not needed, but may be needed in the future.

[makeclean]

Got ya, I wasn't clear what the benefit would be, thanks!