Generalize the temperature scalar type for forward-mode AD - #35
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Finch's field type was fixed to double. This threads a Scalar template parameter (defaulting to double) through Grid, Boundary, Solver, Layer and SolidificationData, so the temperature field can carry a user-supplied arithmetic type. With double the generated code and temperature fields are unchanged; verified bit-identical temperature output and identical solidification records on the single_line case. The differentiated material and source inputs move into a MaterialProperties struct so a caller can supply values of the field scalar type rather than plain doubles read from the input deck. Quantities that only select a branch (solidus, liquidus) and all mesh geometry stay double. Finch_Scalar.hpp adds exp/fmin/fmax dispatch: arithmetic types forward to Kokkos as before, anything else resolves by ADL into the scalar type's own namespace. Finch therefore carries no dependency on any AD library. The optional finch_sensitivity application demonstrates the result with cpp_oti_lib, obtaining d(QoI)/dp for six material and source parameters from a single solve and validating each against central finite differences. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PNkQTS2g7P6dNDybhWRkwz
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@Rombur The PR is open and ready for review. |
streeve
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Rombur
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Co-authored-by: Bruno Turcksin <bruno.turcksin@gmail.com>
Co-authored-by: Bruno Turcksin <bruno.turcksin@gmail.com>
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Rombur
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Aug 10, 2026
Rombur
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Aug 10, 2026
Replace the ad hoc spike run directories with an example under examples/single_line_sensitivity, laid out like the existing single_line example. run_example.sh performs the reference double solve and then four sensitivity configurations: the default finite difference step, a refined step, latent heat removed, and four MPI ranks. The four rank stage now reuses inputs.json Drop the spike specific .gitignore entries, which belong in a local exclude file rather than in the repository.
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Summary
Grid,Boundary,Layer, andSolidificationData, while retainingdoubleas the default.material/source properties plus ADL-based math and value customization
points. Finch core remains independent of any AD library.
finch_sensitivityapplication usingcpp_oti_libtocompute first-order sensitivities for six material and source parameters in
one solve and compare them with central finite differences.
Compatibility
doublewithout source changes.storage remain
double.cpp_oti_libis found; thestandard Finch build has no new dependency.
Validation
clang-format14.0.6 check passed for every changed C++ file.-Wall -Wextra -pedantic -Werror, bothwith and without
cpp_oti_libavailable.single_linetemperature outputs are bit-for-bit identical to upstreammain; solidification records are identical (their parallel emission orderis nondeterministic).
matched the ordinary
doublesolve, and all six derivatives were validatedagainst central finite differences using
FINCH_FD_STEP=1e-8.