- Implements BOTH assembly methods for direct comparison on same problem
- Traditional element assembly: builds 12×12 K_e matrices, scatters to global K
- Nodal assembly: computes 3×3 K_ij blocks directly, accumulates per node
- Test problem: linear elasticity on simple Tet4 mesh
- TestLinearElastic material with Lamé parameters (λ, μ from E, ν)
- B-matrix computation: strain-displacement operator (6×3 per node, Voigt notation)
- Element stiffness: K_e = ∫ B^T C B dV with Gauss integration
- Nodal contribution: spider pattern with 3×3 blocks for coupled nodes
- Matrix-vector product comparison: K*v computed both ways
- Validates numerical equivalence: ‖K_element - K_nodal‖ < tol
- Performance characteristics: element (matrix scatter) vs nodal (direct blocks)
- Architectural differences demonstration: gather-scatter vs direct accumulation
- 542 lines validating nodal assembly correctness and comparing approaches
Jukka Aho