Loading and setting up skims takes longer with sharrow turned on

[Syonv]

This issue is partly a duplicate of issue #688, but I was not able to find a reasonable way to address it.

When running the MWCOG model (which uses ActivitySim v1.3.4), skims normally load in around 5 mins without sharrow activated (from a skims.omx file), however, when running with sharrow, this load time jumps up to around 14 mins. In issue #688, Joe talks about a solution he found which seems to work for the SANDAG setup. However, for the MWCOG model, the detailed solution is not viable, as the full model utilizes a speed feedback loop, where ActivitySim is run 4 times (5 times when sharrow needs to compile). For each of these 4 iterations, the skims are updated and cannot be reused for the next iteration. Thus, caching the skims as a zarr store is not beneficial. Furthermore, I've found that the skims cannot simply be provided as a skims.zarr and must be present in both omx and zarr formats, where providing a dummy (empty) skims.omx does not work.

I also tried the solution found here, by compressing the skims.omx file using "Blosc2:zstd" compression, but I was not successful in reducing the load time.

Why does the load time increase and is there a way to address this with the current ActivitySim version? Also, in the future, would there be a way to provide the skims strictly as a zarr store, without requiring skims.omx to be there?