Draft: Add multithreading to CbmTaskUnpack

This MR adds simple multithreading to CbmTaskUnpack. It is meant as a starting point in this direction and to allow us to gain relevant experience.

A significant performance improvement is achieved by using std::sort with the std::execution::par_unseq parameter when time-sorting all digis in the end.

In addition, the components are processed in parallel, yielding another improvement. Here, the performance gains appear to be limited by the process of adding all digis to a common vector.

Further parallelization inside the components (i.e., on microslice level) is not yet attempted in this MR.

On the mFLES login node, the Unpack tasks runs at about 300 MB/s for our benchmark file.

bin/cbmreco_fairrun -i ~/tmp/1588_node8_1_0000.tsa -c ../reco/tasks/CbmRecoConfigExample.yaml

assigned to @v.friese

changed the description

added 3 commits

• 51551b4e - 1 commit from branch computing:master
• 04c6f00f - Add simple OpenMP multithreading to CbmTaskUnpack
• 94c666e3 - Make OpenMP optional in reco/tasks

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Dear @f.uhlig, @v.friese, I might need some advice.

The CI builds currently fail on two systems, centos7-linux-x86_64-gcc8-fairsoft_apr21p2-fairroot_v18.6.7 and debian10-linux-x86_64-gcc8-fairsoft_apr21p2-fairroot_v18.6.7: The #include <execution> header is not found. However, the file is compiled with -std=gnu++17 and the standard library coming with GCC 8 should include this header, as far as I understand. On debian11-linux-x86_64-gcc10-fairsoft_apr21p2-fairroot_v18.6.7, the build seems to run fine.

Do you have an idea?

added 3 commits

• 1e9a6e4b - 1 commit from branch computing:master
• cdd69123 - Add simple OpenMP multithreading to CbmTaskUnpack
• 58dd5e0f - Make OpenMP optional in reco/tasks

Compare with previous version

marked this merge request as draft

Update: Although part of C++17, the parallel execution functionality is obviously not available on all compilers and platforms. I think we need to check for this in the build system and make the usage of <execution> optional.

I temporarily set this MR back to draft state.

added 95 commits

• 58dd5e0f...0f57474d - 92 commits from branch computing:master
• 04c6f00f - Add simple OpenMP multithreading to CbmTaskUnpack
• 94c666e3 - Make OpenMP optional in reco/tasks
• eba74707 - Merge branch 'master' into openmp_cbmreco

Compare with previous version

mentioned in merge request !828 (merged)

Superseded by !828 (merged)

Can be closed now.

closed