Implementation roadmap for GPU-accelerated nonlinear solver pipeline derived
from CPU reference implementation (newton_krylov_anderson_cpu.jl).
Breakdown of solver pipeline:
- Outer loop: Newton iterations (residual assembly + line search)
- Middle loop: GMRES iterations (matrix-free matvec + Arnoldi)
- Inner operation: Element residual assembly with plasticity
Key GPU kernels identified:
1. Element residual assembly (workhorse kernel, nodal scatter with atomics)
2. Vector operations (standard cuBLAS: axpy, dot, norm)
Four-phase implementation strategy:
1. Single kernel test (residual assembly CPU vs GPU)
2. Matrix-free matvec test (Jacobian-vector product validation)
3. GMRES on GPU (Krylov.jl with CuArrays)
4. Complete pipeline (GPU main loop, CPU Anderson acceleration)
Includes plastic state GPU representation (NTuple vs SymmetricTensor),
kernel launch configuration, and atomic scatter pattern (296 lines).
Jukka Aho