- ElementAssemblyData: Global sparse matrix and force vectors
- ElementContribution: Local element contributions before scatter
- scatter_to_global!() adds element matrices to global system
- compute_residual!() calculates r = f_int - f_ext
- apply_dirichlet_bc!() penalty method for essential BCs
- get_dof_indices() node connectivity to global DOF mapping
- matrix_vector_product() sparse K*v multiplication
- 341 lines: Traditional element-by-element assembly infrastructure