Design for handling both nodal and element fields in nodal assembly:
Architecture:
- Nodes have geometry (immutable)
- Elements have connectivity + fields (immutable struct)
- Nodal fields: displacement, temperature, contact pressure
- Element fields: integration point data (σ, ε_plastic, α, C)
Update pattern:
- Create new field containers (NamedTuples)
- Create new elements with updated fields
- Shallow copy element vector, replace elements
- All immutable (GPU-compatible, thread-safe)
GPU kernel:
- Loops over nodes (nodal assembly)
- Accesses nodal_fields for global quantities
- Accesses element.fields for integration point data
- Gathers from connected elements (node_to_elements)
- No atomic operations (each node owns DOFs)
Material state update:
- Process elements in parallel (Threads.@threads)
- Extract nodal displacements from solution
- Compute strains at integration points
- Run material model (plasticity, damage, etc.)
- Create new elements with updated state
- Return new problem with updated fields
Newton iteration:
- Residual uses element.fields.C (current tangent)
- GMRES with matrix-free matvec (nodal assembly)
- Material update after each iteration
- All data structures immutable throughout
Benchmarks show creating new containers ~1000× faster than deepcopy
Jukka Aho