Fleshed out instructions about DD4hep geometry information

[HenryDayHall]

Currently I get the error

CellIDSvc            INFO Taking the encoding string as specified in dd4hep constant: GlobalTrackerReadoutID
CellIDSvc            INFO LCTrackerCellID::_encoding will be set to system:5,side:-2,layer:6,module:11,sensor:8
AlgorithmManager    ERROR Algorithm of type TrackingCellIDEncodingSvc is unknown (No factory available).
AlgorithmManager    ERROR Unknown error -1342251347

I think it might be because TrackingCellIDEncodingSvc was added here on September 13th. Then on September the 28th, this commit seems to move it to a different namespace?

[tmadlener]

Thanks for opening this PR and clarifying things a bit.

Quick question about the error you observe. Is it possible that the TrackingCellIDEncodingSvc is also still on the algList?

[HenryDayHall]

@tmadlener yes you are right, that was the only problem.

[tmadlener]

I basically just have a few proposals to try and clarify this even further, resp. bring it in line with our usual jargon. I am not entirely sure if all of them are immediately clear to newcomers, but you would be in an ideal position to judge that ;)

Edit: I think the doctest CI workflows are still broken due to another issue, so you don't have to worry about those.

[HenryDayHall]

Current CI issues look like I need to add jupytext to the container. Probably it's not related to these changes. If you like I can take a punt at that in a new MR?

[tmadlener]

We keep track of that here: key4hep/key4hep-spack#547 (a fix is under way but still needs a PR to be merged in spack)

[tmadlener]

Question for @andresailer since we are here already. Do I understand correctly that the CellID service needs to come after the geometry service? Or is the order irrelevant and things will also work if I do

svcList.append(cellIDSvc)
svcList.append(geoservice)

[andresailer]

Question for @andresailer since we are here already. Do I understand correctly that the CellID service needs to come after the geometry service? Or is the order irrelevant and things will also work if I do

svcList.append(cellIDSvc)
svcList.append(geoservice)

Just append to svcList after the service is defined, and the question becomes moot.

[andresailer]

I think it might be because TrackingCellIDEncodingSvc was added here on September 13th. Then on September the 28th, this commit seems to move it to a different namespace?

To clarify this commit never made it to the mainline branch, the PR it belongs to was closed and not merged.

PS: I deleted the move-cellid branch now from this repository.

[tmadlener]

Just append to svcList after the service is defined, and the question becomes moot.

but that might not stop people from defining them in the wrong(?) order. So if the order is important we should maybe clarify that the geometry service has to come first (or at least before the cell ID svc).

[andresailer]

Given

cellIDSvc.GeoSvcName = geoservice.name()

It should stop them from defining them in the wrong order.

[tmadlener]

Excellent point (and good enough for me). If only people would read before they start asking questions ... ;)