Inclusion of the carbon footprint of cached processes

[Llannelongue]

This is to discuss how to present the carbon footprint of cached processes.

Simple example: 3 processes [P1] [P2] [P3]

• First run of the pipeline, all three are run
• Second run of the pipeline, cached [P1] is used, [P2] and [P3] are run

When presenting the carbon footprint of run (2), we can either:

• Take the carbon footprint of [P1] for run (1) and add the carbon footprints of [P2] and [P3] from run (2).
• Or only add the carbon footprints of [P2] and [P3] and ignore the impact of [P1].

Option 1 gives a better estimate of the total carbon footprint of the pipeline if we were to run it again from start to finish on new data let's say. But option 2 gives a more accurate estimate of the true carbon footprint of running step (2). And if adding run (1) + run (2), option 2 should be used (otherwise the footprint of [P1] would get double counted even though it was only run once).

It seems to depend a lot on what users want to do with this information, so perhaps best to give both information in the report so that users can decide what to do?

[skrakau]

Yes, I also think both would be useful in the future