Build alpaka code in GPU-only mode [14.0.x]

[fwyzard]

Build alpaka device code for the CUDA and ROCm back-ends in "GPU only" mode. In this mode, functions marked as ALPAKA_FN_ACC are marked as __device__ functions, and are compiled only for the corresponding GPU device back-ends.

Currently, functions marked as ALPAKA_FN_ACC are marked as __host__ __device__ functions, and may be compiled for both device and host back-ends. The latter leads to linker errors in kernels that use device symbols like threadIdx, blockIdx, etc. that are compiled for the ROCm back-end.

No impact on the HLT performance, as expected.
CMSSW_14_0_4:

Running 4 times over all events with 8 jobs, each with 32 threads, 24 streams and 1 GPUs
   525.9 ±   0.6 ev/s (11800 events, 99.8% overlap)
   522.7 ±   0.5 ev/s (11800 events, 99.9% overlap)
   534.2 ±   0.8 ev/s (11800 events, 99.8% overlap)
   541.6 ±   0.6 ev/s (11800 events, 99.9% overlap)
 --------------------
   531.1 ±   8.5 ev/s

CMSSW_14_0_4 with cms-sw/cmssw#44650 and #9125:

Running 4 times over all events with 8 jobs, each with 32 threads, 24 streams and 1 GPUs
   536.3 ±   0.6 ev/s (11800 events, 99.8% overlap)
   531.2 ±   0.5 ev/s (11800 events, 99.7% overlap)
   558.7 ±   0.4 ev/s (11800 events, 99.5% overlap)
   520.9 ±   0.8 ev/s (11800 events, 99.8% overlap)
 --------------------
   536.8 ±  16.0 ev/s

Backport #9121 to CMSSW 14.0.x for data taking.

[fwyzard]

backport #9121

[cmsbuild]

A new Pull Request was created by @fwyzard for branch IB/CMSSW_14_0_X/master.

@aandvalenzuela, @smuzaffar, @cmsbuild, @iarspider can you please review it and eventually sign? Thanks.
@sextonkennedy, @rappoccio, @antoniovilela you are the release manager for this.
cms-bot commands are listed here

• Backported from Build alpaka code in GPU-only mode #9121

[cmsbuild]

cms-bot internal usage

[fwyzard]

enable gpu

[fwyzard]

please test with cms-sw/cmssw#44650

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-70672a/38660/summary.html
COMMIT: efea939
CMSSW: CMSSW_14_0_X_2024-04-07-0000/el8_amd64_gcc12
Additional Tests: GPU
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmsdist/9125/38660/install.sh to create a dev area with all the needed externals and cmssw changes.

Comparison Summary

Summary:

• You potentially added 36 lines to the logs
• Reco comparison results: 63 differences found in the comparisons
• DQMHistoTests: Total files compared: 49
• DQMHistoTests: Total histograms compared: 3346242
• DQMHistoTests: Total failures: 1355
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3344865
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 48 files compared)
• Checked 205 log files, 166 edm output root files, 49 DQM output files
• TriggerResults: no differences found

GPU Comparison Summary

Summary:

• You potentially added 8 lines to the logs
• Reco comparison results: 35 differences found in the comparisons
• DQMHistoTests: Total files compared: 3
• DQMHistoTests: Total histograms compared: 39740
• DQMHistoTests: Total failures: 1408
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 38332
• DQMHistoTests: Total skipped: 0
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 2 files compared)
• Checked 8 log files, 10 edm output root files, 3 DQM output files
• TriggerResults: no differences found

[smuzaffar]

+externals

@cms-sw/orp-l2 , feel free to include it for next 14.0.X IB/release

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IB/CMSSW_14_0_X/master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @rappoccio, @sextonkennedy, @antoniovilela (and backports should be raised in the release meeting by the corresponding L2)
Notice This PR was tested with additional Pull Request(s), please also merge them if necessary: cms-sw/cmssw#44650

[fwyzard]

@cms-sw/orp-l2 , feel free to include it for next 14.0.X IB/release

However, cms-sw/cmssw#44650 needs to be merged before (or at the same time as) this PR.

[antoniovilela]

Will merge it with cms-sw/cmssw#44650, after passing an IB in master.

[antoniovilela]

+1