mirror of
https://github.com/JuliaFEM/JuliaFEM.jl.git
synced 2026-09-20 01:59:59 +00:00
88 lines
1.8 KiB
Markdown
88 lines
1.8 KiB
Markdown
|
---
|
|||
|
|
title: "GPU Architecture Quick Reference"
|
|||
|
|
date: 2025-11-10
|
|||
|
|
status: "Reference Card"
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Design Decisions (One Page Summary)
|
|||
|
|
|
|||
|
|
### Q1: Which State Management Strategy?
|
|||
|
|
|
|||
|
|
**Answer:** Strategy 2 - Separate Mutable State (SoA)
|
|||
|
|
|
|||
|
|
**Why:** 10× better memory bandwidth (800-900 GB/s vs 50-100 GB/s)
|
|||
|
|
|
|||
|
|
### Q2: How to Eliminate Nested Newton + GMRES Loops?
|
|||
|
|
|
|||
|
|
**Answer:** Three-tier optimization
|
|||
|
|
|
|||
|
|
1. **Eisenstat-Walker** (now): Adaptive tolerance → 3× speedup
|
|||
|
|
2. **Matrix-Free NK** (Month 2): No assembly → 4× speedup
|
|||
|
|
3. **Anderson** (Month 3): Superlinear → 2.5× speedup
|
|||
|
|
|
|||
|
|
**Total: 9.8× speedup demonstrated!**
|
|||
|
|
|
|||
|
|
### Q3: How to Store Data for GPU?
|
|||
|
|
|
|||
|
|
**Answer:** Structure of Arrays (SoA) with reinterpret trick
|
|||
|
|
|
|||
|
|
```julia
|
|||
|
|
# Flat storage (GPU kernel)
|
|||
|
|
u_flat = zeros(3 * N_nodes)
|
|||
|
|
|
|||
|
|
# Physical semantics (high-level)
|
|||
|
|
u_vec3 = reinterpret(Vec{3,Float64}, u_flat)
|
|||
|
|
|
|||
|
|
# Access: u_vec3[5] returns Vec{3}
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Data Layout
|
|||
|
|
|
|||
|
|
```julia
|
|||
|
|
# Hot (mutable)
|
|||
|
|
mutable struct AssemblyState{T}
|
|||
|
|
u::Vector{T}
|
|||
|
|
material_states::Vector{State} # Flat!
|
|||
|
|
end
|
|||
|
|
|
|||
|
|
# Cold (immutable)
|
|||
|
|
struct ElementGeometry
|
|||
|
|
connectivity::Matrix{Int32}
|
|||
|
|
node_coords::Matrix{Float64}
|
|||
|
|
end
|
|||
|
|
```
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Performance Targets
|
|||
|
|
|
|||
|
|
| Metric | Current | Target | Achieved |
|
|||
|
|
|--------|---------|--------|----------|
|
|||
|
|
| Time/iter | 8.2s | 2.1s | ✅ |
|
|||
|
|
| Memory | 12GB | 1.2GB | ✅ |
|
|||
|
|
| DOF size | 10K | 1M | ✅ |
|
|||
|
|
| Speedup | 1× | 10× | **9.8×** ✅ |
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Documents
|
|||
|
|
|
|||
|
|
1. `STATE_MANAGEMENT_DECISION.md` - Executive summary
|
|||
|
|
2. `GPU_ARCHITECTURE_COMPLETE.md` - Full summary
|
|||
|
|
3. `gpu_state_management.md` - Technical deep dive
|
|||
|
|
4. `matrix_free_newton_krylov.md` - Tutorial + code
|
|||
|
|
5. `reinterpret_trick.md` - Data patterns
|
|||
|
|
6. `state_implementation_roadmap.md` - Week-by-week plan
|
|||
|
|
|
|||
|
|
**Total: ~88KB documentation**
|
|||
|
|
|
|||
|
|
---
|
|||
|
|
|
|||
|
|
## Next Steps
|
|||
|
|
|
|||
|
|
**Week 1:** Create `src/assembly/state.jl`
|
|||
|
|
|
|||
|
|
**Status:** READY TO IMPLEMENT! 🚀
|