EDM4hep Discussion

Tuesday 23 May 2023, 09:00 → 10:00 Europe/Zurich

Zoom

Live Notes

EDM4hep Live Notes
==================

Date: May 23, 2023
Indico: https://indico.cern.ch/event/1288446/

Connected: Graeme, Brieuc, Weidong, Tao, Juraj, Sanghyun, Juan, Swathi, Andre, Benedikt, Thomas, Leonhard, Frank, Gerri

Apologies:

## Introduction and General Points

### Upcoming workshops / conferences
https://github.com/orgs/key4hep/projects/4/views/1

   
## Progress and discussion

 

### Frame integration into FW
- https://github.com/key4hep/k4FWCore/issues/94
- Handling of non podio Collections in `DataHandle`. Are these used somewhere? Specifically single integral type or floating point values:
   - https://github.com/key4hep/k4FWCore/blob/master/k4FWCore/include/k4FWCore/DataHandle.h#L82
- https://github.com/key4hep/k4FWCore/pull/100

#### Collection meta data discussion
* See presentation
* Why not add `getParameter` to Collection interface?
   * Interface would not reflect reality (if collection meta data are fixed for lifetime of a file)
   * Boils down to the lifetime of "collection metadata"
* What level are the parameters at? Is it event level?
   * Each Frame has its own parameters, so the Frame lifetime defines the lifetime of the parameters.
* User friendliness of dedicated Frame approach?
   * Can we come up with similar ways to use the `collMD` object in Gaudi and podio?
   * Can we avoid having to explicitly instantiate that in user land?
   * Add a `getCollectionParameters` to Reader/Writer to make this explicit?
       * Would be able to hide details (e.g. category name) 
   

## Podio
* https://github.com/AIDASoft/podio/pulls
* https://github.com/AIDASoft/podio/issues
* https://github.com/orgs/AIDASoft/projects/1/views/1

### Fix reading of multiple files with ROOTFrameReader
* https://github.com/AIDASoft/podio/pull/417
* Merge before tag

### Make branch names for relations more legible for ROOT based I/O 
* https://github.com/AIDASoft/podio/pull/405 
* Is `<collection-name>_<relation-name>` too prone for collisions with e.g. user data?
* Add an underscore to the front as well

### Hashing of collection names for collectionID
* https://github.com/AIDASoft/podio/pull/412
* Using MurmurHash2 in 64 bit -> very low collision probability
   * Increase of `ObjectID` from 64 bit to 96 bit
   * Potential alignment issue in memory
   * File sizes increases as well
* Collision probabilities:
* **Keep 32 bits** and add graceful error message to the termination that occurs on collision

## EDM4hep
* https://github.com/key4hep/EDM4hep/pulls
* https://github.com/key4hep/EDM4hep/issues

## AoB

## Next meeting:
* June 06, 2023 09:00 CET

09:00 → 09:05 Introduction

Speakers: Andre Sailer (CERN), Frank-Dieter Gaede (Deutsches Elektronen-Synchrotron (DE)), Thomas Madlener (Deutsches Elektronen-Synchrotron (DESY))

EDM4hep Github

Podio Github

09:10 → 09:30 Collection metadata with the Frame

Speaker: Thomas Madlener (Deutsches Elektronen-Synchrotron (DESY))

frame_collection_metadata.pdf

09:55 → 09:56 Discussion

Speaker: Dr All