1. Feedback on a first use of the ALFA and O2 software
Barthélémy von Haller

2. Use case Make an existing program publish histograms
Have another program get the histograms
My program uses ROOT6, CMake, C++11 and boost ; it runs on SLC6.
ROOT 6 histogram
Same env as alfa/o2
Should have minimal impact on my programs.
Those programs ultimately will run in o2 facility, today not.

3. Reminder from TDR : O2 stakeholders & SW design
«  ALFA is the result of a common effort of the ALICE and FAIR experiments to provide the underlying communication layer as well as the common parts for a multi-process system. »
 ALFA for the communication

4. Expected steps and usage
Installation
Download a new yum repo file
Yum install alfa
Installs all the necessary dependencies
[Setup environment] (if not installed in standard OS locations)
Execute a bash command or add a line to bashrc
Environment points to the installed software
Documentation
Quick start
Explains the most basic use cases in the simplest possible way
I can copy-paste from it to start using ALFA
General introduction to the library
Classes documentation
Use
CMake
Add find_package(Alfa CONFIG COMPONENTS Base Devices REQUIRED) to my CMakeLists.txt
Add ${ALFA_INCLUDE_DIR} to include_directories
Add ${ALFA_LIBRARIES} to target_link_libraries for my program
My class(es)
#include <…>
… Use stuff from the quick start documentation and build on it
No FindAlfa !

5. Actual steps Installation
There is no ALFA, one has to install FairRoot  Install many dependencies
Some unexpected : Geant, Pythia, GSL
Some already there : ROOT, ZeroMQ, CMake, boost
Everything is downloaded and compiled
Alfaconfig.sh had incompatible options and silent failures
After compilation : 24GB (source+build) + 5.5GB (Install)
Took me 1 day just to finish all compilations successfully

6. Actual steps Setup Documentation Export SIMPATH and FAIRROOTPATH
 Incomplete environment to start using ALFA
Documentation
« Getting started » page from FairRoot is not really fit for O2. It mentions the flp2epn tutorial7 though.
Lack of documentation. Example : no class diagram to get an idea of design. Example : FairMQChannel(string type, string method, string address) -> What are the possible values for type ?
What is a Device ? A Channel ?

7. Actual steps Use CMake My class(es) Compilation Execution
FindFairRoot.cmake -> use FairRootConfig.cmake
At least provide FAIRROOT_LIBRARIES, avoid using link_directories
My class(es)
Inherit from FairMQDevice and uses FairMQChannel by copying parts of AliceO2::flp2epn, but it is already a complex example.
Compilation
Fails because LD_LIBRARY_PATH not properly set
Fails because I have my own ROOT6 somewhere
Fails because my FindROOT.cmake is different from the one in FairRoot
Execution
Crash because … not sure actually. Tried a few things and decided to wait for reinforcement.

8. Recommendations Modularize as previously designed
Split code, create ALFA repo, rename accordingly
Define clear support lines, e.g. mailing lists, for each SW component
Provide packages and repositories
At least compatible with CERN production OS (SLC6, CC7)
[Compatible with other supported OS (Unbuntu, Mac ?)
Aim at the easiest and least impactful usage
See slide numbered 3
Apply specific recommendations
See slides numbered 4-6
AliceO2 specific
Follow the coding conventions
Repository organization
Cf DDS
What ?
When ?
Who ?