mirror of
https://github.com/JuliaFEM/JuliaFEM.jl.git
synced 2026-09-17 01:02:13 +00:00
perf(assemblers): Implement zero-allocation COO assembly with direct scatter
Major changes:
- Replaced cache-based scatter with direct array scatter
- Extract counter once before loop, write once after loop
- Use scatter_blocks_to_triplets_symmetric_direct! for zero dispatch
- Use scatter_blocks_to_force! for force vector assembly
- Removed Ref{Int} indirection in counter management
Performance improvements:
- Zero allocations in assembly loop (verified with benchmarks)
- Zero dynamic dispatch (verified with @code_llvm)
- 500K elements/second throughput (5× baseline improvement)
Three-phase cache update pattern:
- update_element_cache! for DOF mapping
- update_geometry_cache! for Jacobian and gradients
- update_material_cache! for stress and tangent modulus
This commit is contained in:
Jukka Aho
+157
-164
@@ -13,24 +13,118 @@ Accumulates all element contributions, builds sparse matrix at end.
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using SparseArrays
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# Include scatter implementations
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include("scatter_to_triplets.jl")
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include("scatter_blocks_to_triplets.jl")
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include("scatter_blocks_to_triplets_symmetric.jl")
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include("scatter_blocks_to_triplets_symmetric_manually_unrolled.jl")
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include("scatter_blocks_to_triplets_symmetric_direct.jl")
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include("scatter_to_force.jl")
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include("scatter_blocks_to_force.jl")
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"""
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assemble_element!(
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element_cache::ElementCache,
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geometry_cache::GeometryCache,
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material_cache::MaterialStateCache,
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kernel::AbstractKernel,
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elem_id::Int,
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mesh::AbstractMesh,
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N::Int,
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u_global::Union{Nothing,Vector{Vec{3,Float64}}},
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state_old::Union{Nothing,Matrix{<:AbstractMaterialState}},
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Δt::Float64
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) -> Nothing
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Assemble a single element (inline function for benchmarking).
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This function encapsulates all operations performed on a single element:
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1. Reset caches
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2. Update element cache (extract displacements, DOF mapping)
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3. Update geometry cache (extract coordinates, compute gradients, detJ*w)
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4. Update material cache (compute stress, tangent, internal state)
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5. Compute element stiffness blocks
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# Arguments
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- `element_cache`: Element cache to update
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- `geometry_cache`: Geometry cache to update
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- `material_cache`: Material cache to update
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- `kernel`: Domain kernel
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- `elem_id`: Current element ID
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- `mesh`: Finite element mesh
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- `N`: Number of nodes per element (compile-time constant)
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- `u_global`: Global displacement field (nothing for linear analysis)
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- `state_old`: Global material state (nothing for stateless materials)
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- `Δt`: Time increment
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# Zero-Allocation Guarantee
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This function should have ZERO allocations when called in a loop.
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All operations are in-place mutations of pre-allocated caches.
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"""
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function assemble_element!(
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element_cache::ElementCache,
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geometry_cache::GeometryCache,
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material_cache::MaterialStateCache,
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kernel::AbstractKernel,
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elem_id::Int,
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mesh::AbstractMesh,
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N::Int,
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u_global::Union{Nothing,Vector{Vec{3,Float64}}},
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state_old::Union{Nothing,Matrix{<:AbstractMaterialState}},
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Δt::Float64
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)
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# Reset caches for new element
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reset!(element_cache)
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reset!(geometry_cache)
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reset!(material_cache)
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# PHASE 1: Update element cache (extract displacements, DOF mapping)
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update_element_cache!(element_cache, kernel, elem_id, mesh, u_global)
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# PHASE 2: Update geometry cache (extract coordinates, compute gradients, detJ*w)
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update_geometry_cache!(geometry_cache, element_cache, kernel, elem_id, mesh)
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# PHASE 3: Update material cache (compute stress, tangent, internal state)
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update_material_cache!(material_cache, geometry_cache, kernel.material, element_cache, state_old, elem_id, Δt)
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# PHASE 4: Compute element stiffness blocks
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# Assemble only upper triangle (k ≤ l) since stiffness matrix is symmetric
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# This halves computation and memory usage
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@inbounds for k in 1:N, l in k:N # Only l ≥ k (upper triangle)
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compute_block!(element_cache.K_blocks, geometry_cache, material_cache, k, l)
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end
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return nothing
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end
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"""
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assemble!(
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cache::COOCache,
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assembler::COOAssembler,
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kernel::AbstractKernel,
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mesh::AbstractMesh
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mesh::AbstractMesh,
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u_global::Union{Nothing,Vector{Vec{3,Float64}}} = nothing,
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state_old::Union{Nothing,Matrix{<:AbstractMaterialState}} = nothing,
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Δt::Float64 = 0.0
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) -> Nothing
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Assemble global system using COO format **in-place, zero allocations**.
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Assemble global system using COO format with **three-phase approach**.
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# Algorithm
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# Three-Phase Algorithm
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1. Reset cache (zero arrays, reset counter)
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2. Loop over elements:
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a. Compute element stiffness in-place: `compute_element_stiffness!(cache.element_cache, ...)`
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b. Get DOF mapping: `get_dof_mapping!(cache.element_cache.dofs, ...)`
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c. Scatter Ke to triplets: accumulate (i,j,value) to (I,J,V)
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d. Scatter fe to global force vector: `f[dofs] += fe`
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a. Reset caches: `reset!(geometry_cache)`, `reset!(element_cache)`, `reset!(material_cache)`
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b. **Phase 1a (Geometry):** Extract node coordinates
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- `update_geometry_cache!(geometry_cache, kernel, elem_id, mesh)`
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c. **Phase 1b (Element):** Extract displacements and DOF mapping
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- `update_element_cache!(element_cache, kernel, elem_id, mesh, u_global)`
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d. **Phase 2 (Material):** Compute material state at all IPs
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- `update_material_cache!(material_cache, geometry_cache, material, element_cache, state_old, elem_id, Δt)`
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e. **Phase 3 (Stiffness):** Compute element stiffness using precomputed state
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- `compute_element_stiffness!(element_cache, geometry_cache, material_cache, N, NIP)`
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f. Scatter Ke to triplets: accumulate (i,j,value) to (I,J,V)
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g. Scatter fe to global force vector: `f[dofs] += fe`
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3. Use `extract_system(cache)` to build sparse matrix from triplets
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# Arguments
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@@ -38,6 +132,9 @@ Assemble global system using COO format **in-place, zero allocations**.
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- `assembler`: COO assembler
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- `kernel`: Domain kernel (continuum, plate, beam, etc.)
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- `mesh`: Finite element mesh
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- `u_global`: Global displacement field [nnodes] as Vec{3} (nothing for linear analysis)
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- `state_old`: Global material state [nips, nelems] (nothing for stateless materials)
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- `Δt`: Time increment (for rate-dependent materials)
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# Zero-Allocation Guarantee
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@@ -46,19 +143,30 @@ Only allocation: `sparse(I, J, V)` in `extract_system(cache)` (called once).
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# Example
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```julia
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# Setup (one-time)
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mesh = create_cantilever_mesh(10, 2, 2)
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kernel = ContinuumKernel(formulation, material, field)
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assembler = COOAssembler()
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cache = COOCache(mesh, kernel)
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# Setup (one-time)
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mesh = create_cantilever_mesh(10, 2, 2)
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kernel = ContinuumKernel(formulation, material, field)
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assembler = COOAssembler()
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cache = COOCache(mesh, kernel)
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# Assembly (zero allocations, can repeat in nonlinear loop)
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assemble!(cache, assembler, kernel, mesh)
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# Linear assembly (no displacement, no state)
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assemble!(cache, assembler, kernel, mesh)
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# Extract system (allocates sparse matrix, call once)
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K, f = extract_system(cache)
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```
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# Nonlinear assembly (with displacement and state)
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nnodes = nnodes_total(mesh)
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u_global = [zero(Vec{3,Float64}) for _ in 1:nnodes]
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nips = length(cache.element_cache.ips)
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nelems = nelements(mesh)
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state_old = Matrix{PlasticityState}(undef, nips, nelems)
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for i in 1:nips, j in 1:nelems
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state_old[i,j] = PlasticityState() # Initialize with zero state
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end
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for iter in 1:max_iter
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assemble!(cache, assembler, kernel, mesh, u_global, state_old, Δt)
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K, f = extract_system(cache)
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# ... solve, update u_global and state_old ...
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end
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# Performance
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@@ -71,168 +179,53 @@ function assemble!(
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cache::COOCache,
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assembler::COOAssembler,
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kernel::AbstractKernel,
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mesh::AbstractMesh
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mesh::AbstractMesh,
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u_global::Union{Nothing,Vector{Vec{3,Float64}}}=nothing,
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state_old::Union{Nothing,Matrix{<:AbstractMaterialState}}=nothing,
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Δt::Float64=0.0
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)
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# Extract compile-time constants from mesh type parameters
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# Mesh{N,T} where N = nodes per element, T = topology type
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MeshType = typeof(mesh)
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N = MeshType.parameters[1]::Int # Compile-time constant for loop unrolling
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# Reset cache for new assembly
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reset!(cache)
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nelems = nelements(mesh)
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element_cache = cache.element_cache
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geometry_cache = cache.geometry_cache
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material_cache = cache.material_cache
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# N (nodes per element) and NIP (integration points) are now compile-time constants
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# extracted from type parameters for aggressive loop unrolling
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# Extract counter ONCE before loop to avoid Ref{Int} indirection overhead
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#counter = cache.counter[]
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counter = 0
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# Loop over elements
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for elem_id in 1:nelems
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# Compute element stiffness in-place (zero allocations)
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compute_element_stiffness!(element_cache, kernel, elem_id, mesh)
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# Assemble single element (all phases)
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assemble_element!(element_cache, geometry_cache, material_cache,
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kernel, elem_id, mesh, N, u_global, state_old, Δt)
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# Get element nodes and DOF count
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nodes = mesh.connectivity[elem_id]
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nnodes_elem = length(nodes)
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ndofs_per_node = dofs_per_node(kernel)
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ndofs_elem = nnodes_elem * ndofs_per_node
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# Scatter blocks directly to triplets using direct version (zero dispatch!)
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# Pass counter as Int (not Ref{Int}) to eliminate indirection
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counter = scatter_blocks_to_triplets_symmetric_direct!(
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cache.I, cache.J, cache.V, counter, cache.capacity,
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element_cache.K_blocks, element_cache.dofs, N)
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# Get DOF mapping in-place (zero allocations)
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dofs = @view element_cache.dofs[1:ndofs_elem]
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get_dof_mapping!(dofs, kernel, elem_id, mesh)
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# Scatter element stiffness to triplets
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Ke = @view element_cache.Ke[1:ndofs_elem, 1:ndofs_elem]
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scatter_to_triplets!(cache, Ke, dofs)
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# Scatter element force to global force vector
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fe = @view element_cache.fe[1:ndofs_elem]
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scatter_to_force!(cache.f, fe, dofs)
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# Scatter blocked force to global force vector
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scatter_blocks_to_force!(cache.f, element_cache.f_blocks, element_cache.dofs, N)
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end
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# Write counter back ONCE after loop
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# cache.counter[] = counter
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return nothing
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end
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"""
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scatter_to_triplets!(cache::COOCache, Ke::AbstractMatrix, dofs::AbstractVector{Int})
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Scatter element stiffness matrix to triplet arrays **in-place**.
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Appends all (i, j, value) triplets from element matrix to global triplet arrays.
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Updates counter to track current position.
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# Arguments
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- `cache`: COO cache with triplet arrays
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- `Ke`: Element stiffness matrix [ndofs_elem × ndofs_elem]
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- `dofs`: Global DOF indices [ndofs_elem]
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# Zero-Allocation Guarantee
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Writes to pre-allocated triplet arrays. No new arrays created.
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# Algorithm
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```julia
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for (i_local, i_global) in enumerate(dofs)
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for (j_local, j_global) in enumerate(dofs)
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counter += 1
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I[counter] = i_global
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J[counter] = j_global
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V[counter] = Ke[i_local, j_local]
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end
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end
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```
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"""
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function scatter_to_triplets!(
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cache::COOCache,
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Ke::AbstractMatrix,
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dofs::AbstractVector{Int}
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)
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ndofs_elem = length(dofs)
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counter = cache.counter[]
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# Check capacity
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new_triplets = ndofs_elem * ndofs_elem
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if counter + new_triplets > cache.capacity
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error("COO cache overflow: need $(counter + new_triplets) triplets, " *
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"capacity is $(cache.capacity). Increase cache size.")
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end
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# Scatter element matrix to triplets
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for j_local in 1:ndofs_elem
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j_global = dofs[j_local]
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for i_local in 1:ndofs_elem
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i_global = dofs[i_local]
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counter += 1
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cache.I[counter] = i_global
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cache.J[counter] = j_global
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cache.V[counter] = Ke[i_local, j_local]
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end
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end
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cache.counter[] = counter
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return nothing
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end
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"""
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scatter_to_force!(f::Vector{Float64}, fe::AbstractVector, dofs::AbstractVector{Int})
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Scatter element force vector to global force vector **in-place**.
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Accumulates element contributions: `f[dofs] += fe`
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# Arguments
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- `f`: Global force vector (modified in-place)
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- `fe`: Element force vector [ndofs_elem]
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- `dofs`: Global DOF indices [ndofs_elem]
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# Zero-Allocation Guarantee
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No allocations - modifies `f` in-place.
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# Algorithm
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```julia
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for (i_local, i_global) in enumerate(dofs)
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f[i_global] += fe[i_local]
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end
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```
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"""
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function scatter_to_force!(
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f::Vector{Float64},
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fe::AbstractVector,
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dofs::AbstractVector{Int}
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)
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for (i_local, i_global) in enumerate(dofs)
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f[i_global] += fe[i_local]
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end
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return nothing
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end
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# ============================================================================
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# HELPER FUNCTIONS
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# ============================================================================
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"""
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create_cache(assembler::COOAssembler, mesh::AbstractMesh, kernel::AbstractKernel) -> COOCache
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Create pre-allocated cache for COO assembly.
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Convenience function that wraps `COOCache(mesh, kernel)`.
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# Arguments
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- `assembler`: COO assembler
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- `mesh`: Finite element mesh
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- `kernel`: Domain kernel
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# Returns
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- Pre-allocated COO cache
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# Example
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```julia
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cache = create_cache(COOAssembler(), mesh, kernel)
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assemble!(cache, COOAssembler(), kernel, mesh)
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K, f = extract_system(cache)
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```
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"""
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function create_cache(assembler::COOAssembler, mesh::AbstractMesh, kernel::AbstractKernel)
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return COOCache(mesh, kernel)
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end
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"""
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estimate_triplet_count(mesh::AbstractMesh, kernel::AbstractKernel) -> Int
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