Honor ran_seed in deterministic runs#452
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Re-lands #452 on `main`. That pull request was squash-merged into its stacked base `fix/ci-slow-test-gates` (#454), so `main` never received the fix. This branch cherry-picks the squash commit `d8506f9` onto current `main` (`3cfba79`); it applied without conflicts. Deterministic runs ignored `ran_seed` and always produced the default stream, so distinct seeds could not generate independent particle sets. `params.f90` now forwards the configured seed, `test_deterministic_seed.f90` checks that distinct seeds change the stream while the default seed reproduces the previous one, and the orbit-output example input records the seed it uses. ## Verification ### Test fails on main `src/params.f90` reverted to `origin/main`, test kept: ``` $ fo test test_deterministic_seed test_deterministic_seed FAIL 0.11s Summary: 0 passed, 1 failed, 0 skipped ( 0.11s) ``` ### Test passes after fix ``` $ fo test test_deterministic_seed test_deterministic_seed PASS 0.12s Summary: 1 passed, 0 failed, 0 skipped ( 0.12s) ``` `fo build` and `fo lint` pass on the branch (no new warnings; 0 unused imports).
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Fixes #464
Risk tier
Correctness contract
Intended behavior change
ran_seedcontrols the Fortran random stream whendeterministic=.true.. Equal seeds reproduce the stream; different seeds change it.Behavior that must not change
Orbit equations, integrators, field evaluation, loss criteria, parallel dispatch, and deterministic replay for an explicitly fixed seed are unchanged.
Coordinate / unit conventions
No coordinate, unit, boundary, or symmetry convention changes.
Numerical invariants
Only sampled initial conditions may change. The historical NetCDF fixture now explicitly requests seed 42. The chartmap pipeline keeps its existing calculations, assertions, and plots.
Tests added
fopipelineGolden-record impact
Failure modes considered
Same-seed non-reproducibility, ignored distinct seeds, invalid orbit fixture sample, and plot-enabled chartmap runtime exceeding its former 60 s timeout.
Manual validation
The NetCDF fixture passes with its historical seed 42. The plot-enabled chartmap pipeline passes in 59.71 s with a 120 s timeout.
Verification
Test fails on main
Test passes after fix