Small Model Optimizations

[jasondegraw]

It would be helpful to have an object similar to the PerformancePrecisionTradeoffs object that would be the collection location for options/settings that provide speed improvements for "small" models. "Small" in this context means very few zones, simpler systems, etc. Admittedly, I'm misusing "optimizations" here, but the idea would be to have options for

• outputs,
• shading,

and other things that can help speed up smaller models. Adding these into the existing PerformancePrecisionTradeoffs object would be OK too, but the name is a bit worse there (the idea isn't to trade precision for performance, just to do things that are better for performance of small models).

[amirroth]

I assume that for small models, input/initialization and output account for a larger fraction of simulation time vis-a-vis the core time-marching piece. And so performance optimizations that target small models, as opposed to ones that target all models or large models, would focus on those pieces. Now, there are certainly things that we can do to improve input processing/initialization and outputs, but I'm not sure that many of those things can be cast as "tradeoffs" because I don't really see them as having a precision dimension.

That said, things to help with input processing:

• Continue transition from IDD to epJSON and possibly optimize epJSON access idioms and methods.
• There are a number of possible optimizations in EPW file processing (have already opened up an issue for this, but there is a more significant follow-on possibility which is to cache the interpolated weather data structure in binary form and and just memory-map that in).
• Optimized processing of other input files (sounds like this is a done deal for Schedule files).
• Cross-simulation caching, e.g., CTF calculations, shading.

Things to help with initialization:

• Continue moving constant data from const std::string to constexpr std::string_view and ArrayXD<T> const to constexpr std::array<T>.
• Factor/split up some large structures and only allocate/initialize portions corresponding to features that are actually used during the simulation.
• Do not allocate or initialize reporting variables that are not used during the particular simulation.

Things to help with output:

• Reduce number of default reports.
• Write output (especially time-series) in binary form and parse out later if needed.