EDM4hep Discussion

Tuesday 15 Jun 2021, 09:00 → 10:01 Europe/Zurich

Zoom

Live Notes

    * Accepted
    
* ACAT
    * https://indico.cern.ch/event/855454/
    * submission deadline postponed: Aug 29
    
* FCC week
    * https://indico.cern.ch/event/995850
    * (Short) software session on Wed 30th, 11h
        * Key4hep - Frank
        * FCCSW migration - Valentin
        * FCCAnalyses - Clement
 
 * PyHEP (virtual) workshop 2021
     * https://indico.cern.ch/event/1019958/

## Progress and Discussion

## Podio

### Make a tag(?)
* last tag is 00-13 (Dec 3, 2020)
* Currently need `podio@master` in key4hep-stack

###  Support for multiple input sources in parallel
* https://github.com/AIDASoft/podio/issues/190
* Please read and maybe comment
* Presentation by Benedikt at next meeting

### Benchmarking

* Discuss how to integrate with validation in Key4hep

### Issues/PRs

* Fixed width integer types
    * https://github.com/key4hep/EDM4hep/issues/112
    * https://github.com/AIDASoft/podio/pull/186 for podio support, merged
    * Move to fixed width types in edm4hep?
        * Makes sense and "doesn't hurt us".
    * Doubles/floats? Are they are guaranteed to be fixed size?
        * standard defines only minimum width
        * `<cstdint>` available for floats?
            * boost has fixed width float types
            * In `std` only means to check if they are IEEE 754 compliant and width
            
* Disentangle storage and collection interface and reference collections
    * https://github.com/AIDASoft/podio/pull/197
    * Essentially ready for review, few small-ish TODO items left

#### Constness in python
* Currently solved by `Const` classes
* Also useful for `auto` type deduction, where `const auto` can be necessary otherwise to get something fully correct
* LCIO solved with flag in collections
* Do we need python writing?
    * probably yes, for writing ntuple like data

#### Heap-use-after-free

* https://github.com/AIDASoft/podio/issues/174
* Not a problem in frameworks, but if collections used outside of them
* Deep inside the memory management of podio, so not easy to fix
* Happens more often with clang than with gcc, but could be compiler options.
    * Flagged by address-sanitizer
* Maybe requires deep changes. Change for reference counting of object classes.

#### c++ concepts
* BH: add compile time checks for class behaviours: e.g., movable

#### issue w/ ROOT and (vectors of) non-copyable collections
* happens in ROOT 6.22 
* PM: there is a patch available in LCG repository
    * ROOT team is working on a general solution
* Still relevant for us? 

#### What are the different branches in the root file?
* https://github.com/AIDASoft/podio/issues/169
* Encode more information in the _relation_ branch names?
* Related to use in RDataFrame/RNTupe, directly looking at root file content
* Are branch names an implementation detail?
* backward compatibility "Impossible" (?)

#### Schema Evolution
- https://github.com/AIDASoft/podio/issues/86
- Discussion: https://indico.cern.ch/event/1030566/

#### Multi-Threading

#### "event class" in podio

* Currently being perceived

### PRs
* https://github.com/AIDASoft/podio/pulls

### Meta Data

#### Usage of "metadata" for user defined data
* need to check if current implementation addresses all use cases
* need test use-cases

### EventStore

### Features

* Subset collections?

#### framework ROOTWriter
* Could be refactored to use more standalone things via Gaudi Tools and Services
* Could potentially more easily write `std::vector`s or other "generic" types
    * Ideally put "generic" data types also in standalone podio
    * How to best allow for "extensions" to an EDM? 
    
## LCIOConverters
* https://github.com/key4hep/k4LCIOReader

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

### cellID decoding functionality in EDM4hep is missing
* https://github.com/key4hep/EDM4hep/issues/115
* pull request to fix it coming

### User defined collections as proper datatypes
* https://github.com/key4hep/EDM4hep/pull/114
* Type is `UserFloat` and not `float` -> APIs have to take `UserFloat`
    * A bit "suprising" that it is not possible to simply store a `float`
    * Needs proper documentation
* Something similar in FCC-edm with clash on macOS due to `Float.h` header file
* Benedikt: Be more strict? E.g. only allow to store user data if there is also metadata in the file.
    * For one parameter branch name could serve as "metadata"
    * Would make it more explicit, but also remove a bit of flexibility
    * Use utility class to enforce this

### MCParticle Endpoint
* https://github.com/key4hep/EDM4hep/issues/113
* Keep podio simple by not allowing getters/setters to access multiple internal states. Use utility functions for this use case, if needed.

### EDM4hep tools
https://github.com/key4hep/EDM4hep-utils

### Issues

## AOB

### Next meeting:

* June 29, 2021

 

09:00 → 09:05 Introduction

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

EDM4hep Github

Podio Github

10:00 → 10:01 Discussion

Speaker: Dr All