[SPH] migrate compute omega from shamrock pre-history to modern age

[tdavidcl]

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[gemini-code-assist]

Summary of Changes

Hello @tdavidcl, 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 significantly modernizes the compute_omega function within the SPH (Smoothed Particle Hydrodynamics) module. The primary goal is to transition the computation to a more efficient and scalable distributed kernel call mechanism. This refactoring streamlines the code, improves how data is handled through structured field references, and prepares the SPH computations for better performance in a distributed computing environment.

Highlights

• Modernized compute_omega Function: The compute_omega function has been entirely refactored to utilize a modern distributed kernel call mechanism, moving away from an older, patch-data-centric approach.
• Distributed Kernel Integration: The computation now leverages sham::distributed_data_kernel_call for parallel execution across distributed data, enhancing scalability and performance.
• Improved Data Management: Introduction of FieldRefs and DDPatchDataFieldRef provides a more structured and efficient way to handle field data references within the solver graph.
• Inlined Computation Logic: The core omega calculation logic, previously abstracted, is now directly embedded within a lambda function passed to the distributed kernel, making the computation more self-contained and explicit.

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[gemini-code-assist]

Code Review

This pull request refactors the compute_omega function to use the modern distributed_data_kernel_call infrastructure, which is a good step forward. The implementation correctly sets up the distributed call.

However, I've found a critical issue in the new kernel logic where it seems to be using an incorrect density value for the omega correction factor calculation. Specifically, it uses a theoretical density rho_ha instead of the summed SPH density rho_sum, and the latter is calculated but left unused. This will likely lead to incorrect physical results. My review includes a suggestion to fix this.

Please address this critical point to ensure the correctness of the simulation.

[gemini-code-assist]

The calculation of omega_a appears to be using rho_ha (a theoretical density) instead of rho_sum (the actual SPH density summation). The variable rho_sum is calculated in the neighbor loop but is currently unused, which strongly suggests it should be used here. Using rho_sum is consistent with the standard SPH formulation for the variable smoothing length correction factor.

Additionally, a check should be added to prevent division by zero when rho_sum is zero (e.g., for isolated particles), in which case omega_a should be 1.

Suggested change

	using namespace shamrock::sph;
	Tscal rho_ha = rho_h(part_mass, h_a, Kernel::hfactd);
	Tscal omega_a = 1 + (h_a / (3 * rho_ha)) * part_omega_sum;
	omega[id_a] = omega_a;
	Tscal omega_a = 1.0;
	if (rho_sum > 0.0) {
	omega_a = 1.0 + (h_a / (3.0 * rho_sum)) * part_omega_sum;
	}
	omega[id_a] = omega_a;

[github-actions]

Workflow report

workflow report corresponding to commit 94080df
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
black....................................................................Passed
ruff check...............................................................Passed
Check doxygen headers....................................................Passed
Check license headers....................................................Passed
Check #pragma once.......................................................Passed
Check SYCL #include......................................................Passed
No ssh in git submodules remote..........................................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 : 0
New warnings : 0
Warnings count : 7955 → 7955 (0.0%)

Detailed changes :