Open Questions

Systematics Handling

Currently every systematics-aware tool implements the ISystematicsTool interface. While that technically works, it does come with limitations, ranging from thread-safe concurrent tool usage to efficient implementations. A lot of these also apply to use in EventLoop/Athena.

Integration with CP Algorithms

There is a lot of similarity in design between the columnar accessors and the systematics data handles used in the CP Algorithms. It feels like it ought to be possible to consolidate here.

Data dependencies for AthenaMT

In principle the columnar accessors give very precise data dependency information, more than one would usually get from Athena tools (i.e. per decoration, not per container). However, it is not currently connected at all, and the container names are typically not configured in xAOD mode.

Configuration

There is a lot of non-trivial configuration code in the CP Algorithms that should ideally be shared or reused for the columnar tools.

Histogram Handling

We demonstrated that we can write far faster histogram implementations than TH1, but there is no concrete plan for how to use them for columnar tools. In the simplest case we'd just provide a drop-in replacement for TH1, but the more columnar we can make it, the faster the implementation will be.