Apply GPU optimizations to TLSPH

[efaulhaber]

Based on trixi-framework/PointNeighbors.jl#154. Tests will pass once PointNeighbors 0.6.6 is released.

[Copilot]

Pull request overview

This PR refactors Total Lagrangian SPH (TLSPH) neighbor interactions to better match GPU-friendly execution patterns (per-particle threading, reduced memory traffic, fewer repeated loads), following the newer PointNeighbors neighbor-iteration approach.

Changes:

• Refactor TLSPH deformation gradient and RHS assembly to use per-particle @threaded loops with foreach_neighbor, accumulating into Refs to reduce global writes.
• Optimize penalty force and viscosity kernels for GPU performance (preload deformation gradients, use div_fast, and use smoothing_kernel_unsafe after cutoff filtering).
• Add a SIMD-based fast path for extracting 2×2 matrices (extract_smatrix) and wire in the SIMD dependency; update tests’ mock systems accordingly.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test/systems/tlsph_system.jl	Updates TLSPH test mock system to a concrete struct (GPU-friendly) and adjusts numeric literals.
test/schemes/structure/total_lagrangian_sph/rhs.jl	Updates RHS tests’ mock system layout and adds deformation_gradient stub required by new RHS path.
src/schemes/structure/total_lagrangian_sph/viscosity.jl	Threads deformation gradient through viscosity path and applies div_fast in hot divisions.
src/schemes/structure/total_lagrangian_sph/system.jl	Reworks deformation gradient assembly into per-particle neighbor loops with reduced memory writes.
src/schemes/structure/total_lagrangian_sph/rhs.jl	Reworks RHS assembly similarly; passes deformation gradients into penalty/viscosity for fewer loads.
src/schemes/structure/total_lagrangian_sph/penalty_force.jl	Converts penalty force to an in-place accumulator API and switches to unsafe kernel + fast divisions.
src/schemes/boundary/wall_boundary/system.jl	Adds smoothing_kernel_unsafe specialization for wall boundary systems.
src/general/neighborhood_search.jl	Adds foreach_neighbor wrapper around PointNeighbors neighbor iteration.
src/general/abstract_system.jl	Adds extract_smatrix Val-specialization and a SIMD 2D fast path.
src/TrixiParticles.jl	Imports SIMD module for use in extract_smatrix.
Project.toml	Adds SIMD dependency + compat; minor reordering of weakdeps/extensions entries.

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[codecov]

Codecov Report

❌ Patch coverage is 74.71264% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 67.26%. Comparing base (379db88) to head (d5766f0).

Files with missing lines	Patch %	Lines
...es/structure/total_lagrangian_sph/penalty_force.jl	14.28%	12 Missing ⚠️
...chemes/structure/total_lagrangian_sph/viscosity.jl	16.66%	5 Missing ⚠️
src/schemes/boundary/wall_boundary/system.jl	0.00%	3 Missing ⚠️
src/general/abstract_system.jl	84.61%	2 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (379db88) and HEAD (d5766f0). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (379db88)	HEAD (d5766f0)
total	1	0

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1139       +/-   ##
===========================================
- Coverage   89.06%   67.26%   -21.81%     
===========================================
  Files         128      128               
  Lines        9868     9857       -11     
===========================================
- Hits         8789     6630     -2159     
- Misses       1079     3227     +2148     

Flag	Coverage Δ
total	?
unit	67.26% <74.71%> (+0.08%)	⬆️

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[efaulhaber]

/run-gpu-tests

[efaulhaber]

/run-gpu-tests

[Copilot]

Pull request overview

Copilot reviewed 14 out of 15 changed files in this pull request and generated 3 comments.

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[efaulhaber]

/run-gpu-tests