Project Meeting 2023.08.22

Agenda

• Numeric Data Type Update
• Admin
  • Response to Miller Editorial - Final
  • Partners Only Meeting 8/24: Phase 9 Procurement
  • ActivitySim Drive

Action Items / Key Decisions

Meeting Notes

Numeric Data Type Update

• Overview of Approach
  • There are different types of options for numeric values: integer type (8, 16, 32, or 64) with signed (range of -128 to 127) or unsigned (range of 0 to 255).
  • For most variables, we'd be safe to use unsigned int8. However, when we do numeric operations on unsigned int8, a negative could be produced, which could default to 255. For these reasons, it was recommended to move forward without using unsigned integers.
  • For signed integers, there is numeric overflow with lower byte integer specifications. For example, there are operations that calculate a chaperone weight. Each individual variable is int8; when the weight is calculated, there’s an overflow with the calculations. The process currently does not smartly upflow the number of integer bytes that are needed. A potential solution would be to resolve these cases by manually upcast the variables as int64.
• Implications
  • Developers would need to manually upcast in the code and users need to keep this in mind when creating formulas in UECs and preprocessors.
  • There will be savings in memory but have cost in that needs to be very intentional in code/UECs.
  • Concern that it wouldn’t be obvious on the user end if this process is going to mess up calculations.
  • Some risk on the developer side; but larger risk on the user side, it’s complicated and not clear when someone messes it up.
• Next Steps
  • Sijia to put together a memory profile to see memory savings with the downcasting, to see if it’s worth the effort
  • Need to make a decision on whether to downcast numerics, but need a little more analysis from Sijia to make that decision
  • There is an issue under the sharrow implementation (skim values are not being returned correctly on time period categoricals). Sijia and Jeff to work through implementing a solution.

Admin

• The response to Eric Miller editorial has been finalized
  • If interested as a signatory, one representative person from each agency is requested
• Focus of partners only meeting will be to focus on how to do Phase 9 procurement
• ActivitySim Google Drive
  • Joe has created and is moving things around
  • Please ignore any notifications about resharing, annoying emails, etc.