[Scheduler] omp parallelize LB

[tdavidcl]

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[github-actions]

Thanks @tdavidcl for opening this PR!

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Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on improving the performance of the load balancing logic by parallelizing key sections of the code using OpenMP. It also reduces logging verbosity by adding a log level check before printing debug messages. The changes primarily affect LoadBalanceStrategy.hpp and HilbertLoadBalance.cpp.

Highlights

• Parallelization: The load balancing logic in LoadBalanceStrategy.hpp and HilbertLoadBalance.cpp was parallelized using OpenMP to improve performance.
• Patch Packing: The apply_node_patch_packing function in HilbertLoadBalance.cpp was modified to use OpenMP for parallel execution, replacing the previous SYCL implementation.
• Logging: Added a check for log level before printing debug messages in HilbertLoadBalance.cpp and LoadBalanceStrategy.hpp to reduce verbosity.

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Code Review

This pull request aims to improve performance by parallelizing load balancing logic using OpenMP. The changes are generally well-implemented, converting sequential loops to parallel ones and optimizing related code structures. However, a critical data race was identified in one of the newly parallelized loops in HilbertLoadBalance.cpp, which could lead to non-deterministic behavior. The review includes a specific comment with a suggested fix for this issue.

[github-actions]

Workflow report

workflow report corresponding to commit a4110ed
Commiter email is timothee.davidcleris@proton.me
GitHub page artifact URL GitHub page artifact link (can expire)

Pre-commit check report

Pre-commit check: ✅

trim trailing whitespace.................................................Passed
fix end of files.........................................................Passed
check for merge conflicts................................................Passed
check that executables have shebangs.....................................Passed
check that scripts with shebangs are executable..........................Passed
check for added large files..............................................Passed
check for case conflicts.................................................Passed
check for broken symlinks................................................Passed
check yaml...............................................................Passed
detect private key.......................................................Passed
No-tabs checker..........................................................Passed
Tabs remover.............................................................Passed
Validate GitHub Workflows................................................Passed
clang-format.............................................................Passed
ruff check...............................................................Passed
ruff format..............................................................Passed
Check doxygen headers....................................................Passed
Check license headers....................................................Passed
Check #pragma once.......................................................Passed
Check SYCL #include......................................................Passed
No ssh in git submodules remote..........................................Passed
No UTF-8 in files (except for authors)...................................Passed

Test pipeline can run.

Clang-tidy diff report

No relevant changes found.
Well done!

You should now go back to your normal life and enjoy a hopefully sunny day while waiting for the review.

Doxygen diff with main

Removed warnings : 7
New warnings : 7
Warnings count : 8366 → 8366 (0.0%)

Detailed changes :

- src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:194: warning: Compound shamrock::scheduler::details::LBMetric is not documented.
- src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:195: warning: Member min (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
- src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:196: warning: Member max (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
- src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:197: warning: Member mean (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
- src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:198: warning: Member stddev (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
+ src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:204: warning: Compound shamrock::scheduler::details::LBMetric is not documented.
+ src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:205: warning: Member min (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
+ src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:206: warning: Member max (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
+ src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:207: warning: Member mean (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
+ src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:208: warning: Member stddev (variable) of struct shamrock::scheduler::details::LBMetric is not documented.
- src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:253: warning: The following parameter of shamrock::scheduler::load_balance(std::vector< TileWithLoad< Torder, Tweight > > &&lb_vector, i32 world_size=shamcomm::world_size()) is not documented:
+ src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:263: warning: The following parameter of shamrock::scheduler::load_balance(std::vector< TileWithLoad< Torder, Tweight > > &&lb_vector, i32 world_size=shamcomm::world_size()) is not documented:
- src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:44: warning: Member LoadBalancedTile(TileWithLoad< Torder, Tweight > in, u64 inindex) (function) of struct shamrock::scheduler::details::LoadBalancedTile is not documented.
+ src/shamrock/include/shamrock/scheduler/loadbalance/LoadBalanceStrategy.hpp:46: warning: Member LoadBalancedTile(TileWithLoad< Torder, Tweight > in, u64 inindex) (function) of struct shamrock::scheduler::details::LoadBalancedTile is not documented.