Imported from wenbinyugroup/gebt (AGENTS.md). Install upstream with npx skills add wenbinyugroup/gebt. Copyright stays with the author.

AGENTS.md

What This Is

GEBT — a Fortran solver for Geometrically Exact Beam Theory (v4.8). Mixed-formulation intrinsic beam theory compatible with VABS cross-sectional properties.

Language and Build

• Source language: Fortran — fixed-form .f (legacy libraries) and free-form .f90 (application code). pyproject.toml is for Sphinx doc tooling only, not the main application.
• Compiler: gfortran (primary, cross-platform). Intel ifx also supported as fallback.
• Build (CMake, recommended):
  • Windows: .\tools\build_msvc.bat (requires gfortran on PATH + MSYS2 OpenBLAS/ARPACK)
  • Linux: cmake -B build . && cmake --build build
  • CMake auto-detects system libraries via find_library; falls back to bundled sources if not found.
  • Link order: arpack → OpenBLAS → gomp (static libs, order matters).
  • gfortran builds use -static-libgfortran -static-libgcc on Windows to avoid a UCRT heap conflict with TRIM() temporaries.
• Windows MSYS2 dependencies: pacman -S mingw-w64-ucrt-x86_64-openblas mingw-w64-ucrt-x86_64-arpack
• Intel ifx build (fallback): .\tools\build_ifx.bat (requires Intel oneAPI command prompt)
• Legacy Makefile: cd tools && make install (gfortran, reads tools/gebtMake for source list).

Architecture

Entry point: src/main.f90 → calls Input (IO module) → Analysis → Output (IO module).

Module dependency chain (approximate):

GlobalDataFun → TimeFunction, PrescribedCondition → InternalData →
Preprocess → Element → Member → System → Solve, EigenSolve → Analysis → IO

Bundled libraries in src/: MA28 (sparse linear solver), BLAS, LAPACK. ARPACK replaced by system arpack-ng when available.

Fortran Coding Conventions

Documented in src/GlobalDataFun.f90:1-50. Key rules:

• Global constants, Fortran keywords, and intrinsic functions: UPPERCASE
• User-defined procedures: CamelCase (e.g. MySubroutine)
• All other variables: lowercase_with_underscores
• Always use IMPLICIT NONE
• Never use STOP in subroutines — return error message instead
• Use USE ModuleName, ONLY: ... for imports
• PRIVATE by default; explicitly PUBLIC only what is needed
• Include a data dictionary in program unit headers

Running / Testing

• No automated test suite. Test cases in test/ and examples/ are manual input/output file pairs.
• To run: execute the compiled binary, which reads a .dat input file. It produces:
  • .dat.ech — echo of inputs
  • .dat.out — results
  • .dat.ini — initial conditions (for dynamic analyses)
• Test subdirectories: simple/, dynamics/, strip/, vr7/, naca0015/, issues/

Documentation

• Sphinx docs in doc/. Build: cd doc && make html
• CI (build_sphinx_doc.yml) builds and deploys to gh-pages on push to main.
• PDF manuals are in doc/ (not version-controlled output).
• doc/requirements.txt lists Sphinx dependencies (also duplicated in pyproject.toml).

Python Environment

• Python 3.10, managed with uv (see uv.lock).
• Purpose: Sphinx documentation only — not used for the Fortran application.