4.7 KiB
Smagorinsky baseline/candidate helper diagnostic
This validation-only diagnostic compares exact d79 production headers with a temporary candidate. It does not modify production source. The candidate changes only the D2Q9 and D3Q19 closed-form factors from 18 to 18 sqrt(2), plus comments defining |S| = sqrt(2 S:S) and self-consistent effective tau. The small reviewed patch and expected header hashes are in tests/validation/les/data; no copied headers, solver trees, raw results, or binary fixtures are versioned.
Prepare and verify on the CPU
From the repository root, choose a new output directory:
python tests/validation/les/prepare.py --output-dir output/les-host/candidate
python tests/validation/les/test_candidate.py --candidate-dir output/les-host/candidate --output output/les-host/host_results.json
Preparation checks both actual production header hashes against d79, copies only descriptors.cuh and turbulence_smag.cuh into output-local baseline/patched include trees, applies the reviewed patch only to the latter, and verifies all four resulting hashes. It refuses an existing candidate directory. The host test verifies candidate hashes again and refuses an existing evidence file. The Git branch HEAD may include validation commits; header content, rather than HEAD identity, is the pin.
The independent host oracle constructs second-order Hermite populations and solves the independently derived quadratic by bisection:
tau * (tau - tau0) = 9 Cs^2 ||Pi_neq|| / (sqrt(2) rho)
There are 736 parameter cases, covering D2Q9/D3Q19; Cs=0,.08,.16,.24; tau0=.6,.8,1.2; rho=.7,1,1.3; equilibrium, isotropic stress, pure shear, and trace-free diagonal extension; all coordinate planes and both signs; density-scaled Pi and separate fixed-Pi/nonunit-rho probes. The test checks quadratic residuals, closed/default-three/converged-200 iterations, bit-identical unchanged iterative output, and an additional explicit cap-active manufactured probe. Existing g++ and Python stdlib are sufficient; no installation is attempted. Compilation products are temporary. Previously reviewed host maxima were omega error 1.394302e-7 and quadratic residual 1.201202e-7; this is not CUDA fast-math evidence.
Authorized GPU diagnostic
Use the existing working PyCUDA/NumPy environment and an explicitly selected device, through the same serialized GPU launch owner as the other campaigns:
CUDA_VISIBLE_DEVICES="$VERIFIED_IDLE_GPU" python tests/validation/les/run_gpu.py --run-gpu --device 0 --output-dir output/les-gpu
Device 0 is the logical device after CUDA visibility filtering. The output directory must not exist. The runner materializes and verifies the isolated include trees under output/les-gpu/candidate, then runs baseline and patched processes sequentially. Each process compiles one SourceModule at a time synchronously and synchronizes each probe. There are no background jobs, worker pools, or parallel compiler calls. No machine contact, device selection, reservation, or environment setup is performed by the runner.
Each version has exactly 48 scalar GPU cases, 96 total: D2Q9/D3Q19, Cs=.16/0, equilibrium/shear/isotropic/cap-active manufactured stress, and closed/default-three/converged-200 branches. This is the frozen GPU matrix, not the expanded 736-case host matrix. Outputs baseline.json and patched.json contain raw scalar omega values and device name. Completion means only the diagnostic executed; an independent comparison against the declared host oracle is still required. A failed run leaves partial evidence for inspection and must not be overwritten.
Interpretation and limits
Full-stress versus deviatoric-stress selection, iterative viscosity cap, iteration count/relaxation, omega guards, collision dispatch, and AMR guards remain unchanged. Closed and iterative paths intentionally remain different for isotropic or cap-active stresses. No settings or Cs defaults change. High stress is a helper diagnostic, not an admissible flow-state claim.
The corrected scalar formula is justified only under the stated stress-strain estimate. MRT full-trace stress does not generally share one shear relaxation rate, so its bulk coupling remains uncertified. Force-corrected non-equilibrium stress and Guo-force interaction also remain uncertified. These manufactured tests are unforced and do not cover full TRT/MRT collision, streaming modes, shifted storage, walls/Jets, flow solutions, or 3D turbulence. Existing guard statements are preserved, not newly comprehensively tested; the main matrix is guard-inactive. No AMR LES support is added or enabled.
Production integration and removal of this temporary candidate fixture are separate decisions after GPU and applicable flow evidence. CPU success alone does not approve a production change.