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refactor(physics): Implement double-dispatch architecture

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Major API refactoring: replace mutable ElasticityPhysicsType with
type-parametric Physics struct for compile-time dispatch.

New type hierarchy:
- AbstractField: What we solve (Displacement{3}, Temperature, etc.)
- AbstractFormulation: How we discretize (ContinuumFormulation, BeamFormulation)
- AbstractMaterial: Material behavior (LinearElastic, NeoHookean)
- AbstractMesh: Mesh container

Physics{Formulation, Field, Mesh, Material} enables natural dispatch:
  assemble(::Physics{ContinuumFormulation{FullThreeD}, Displacement{3}, M, Mat})
  assemble(::Physics{BeamFormulation{Timoshenko}, DisplacementRotation{3}, M, Mat})

Type parameter order prioritizes Formulation for dispatch hierarchy.

Breaking changes:
- Old: Physics(Elasticity, "name", 3)
- New: Physics(name=..., mesh=..., field=Displacement{3}(),
               formulation=ContinuumFormulation{FullThreeD}(), material=...)
- Deprecate: add_elements!() - Physics references Mesh, doesn't own elements

Benefits:
- Type stability: All types known at compile time
- Dispatch: Specialized methods for formulation/field combinations
- Extensibility: New formulations/fields without modifying core
- Performance: No runtime type checks, optimal codegen

This is foundation for the NEW API (TDD tests, Nov 14 2025).
This commit is contained in:
Jukka Aho
2025-11-14 23:22:42 +02:00
parent b485886324
commit 9b22df8d3c
1 changed files with 371 additions and 40 deletions
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src/physics_api.jl
+371 -40
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@@ -7,24 +7,175 @@ Backend-agnostic elasticity API
This file defines the user-facing API that works regardless of backend (CPU or GPU).
"""
# ============================================================================
# Abstract Types for Mesh, Material, Field, and Formulation
# ============================================================================
"""
Elasticity <: FieldProblem
AbstractMesh
Elasticity physics problem type.
Abstract type for all mesh structures.
Properties:
- `formulation`: `:continuum` (3D solid) or `:plane_stress`, `:plane_strain`
- `finite_strain`: Enable geometric nonlinearity
- `geometric_stiffness`: Include stress-dependent stiffness
Concrete subtypes: Mesh{T<:AbstractTopology}
"""
mutable struct ElasticityPhysicsType <: FieldProblem
formulation::Symbol # :continuum (3D)
finite_strain::Bool # Geometric nonlinearity
geometric_stiffness::Bool # Stress-dependent stiffness
end
abstract type AbstractMesh end
const Elasticity = ElasticityPhysicsType
ElasticityPhysicsType() = ElasticityPhysicsType(:continuum, false, false)
"""
AbstractMaterial
Abstract type for all material models.
Concrete subtypes: LinearElastic, NeoHookean, PerfectPlasticity, etc.
"""
abstract type AbstractMaterial end
# ============================================================================
# Abstract Types for Field and Formulation (Double Dispatch)
# ============================================================================
"""
AbstractField
Abstract type for field variables we solve for.
Subtypes define what physical quantity is being solved:
- `Displacement{Dim}`: Displacement field (3D, 2D, etc.)
- `Temperature`: Temperature field
- `DisplacementRotation{Dim}`: Displacement + rotation (beams, shells)
"""
abstract type AbstractField end
"""
Displacement{Dim} <: AbstractField
Displacement field with Dim components per node.
# Examples
- `Displacement{3}()`: 3D displacement (ux, uy, uz)
- `Displacement{2}()`: 2D displacement (ux, uy)
"""
struct Displacement{Dim} <: AbstractField end
"""
dofs_per_node(field::AbstractField) -> Int
Number of degrees of freedom per node for this field type.
"""
dofs_per_node(::Displacement{Dim}) where Dim = Dim
"""
Temperature <: AbstractField
Temperature field (scalar per node).
"""
struct Temperature <: AbstractField end
dofs_per_node(::Temperature) = 1
"""
DisplacementRotation{Dim} <: AbstractField
Combined displacement and rotation field (for beams, shells).
DOFs per node: 2*Dim (Dim displacements + Dim rotations)
- 3D: 6 DOFs (ux, uy, uz, θx, θy, θz)
- 2D: 4 DOFs (ux, uy, θz, warping)
"""
struct DisplacementRotation{Dim} <: AbstractField end
dofs_per_node(::DisplacementRotation{Dim}) where Dim = 2 * Dim
"""
AbstractFormulation
Abstract type for discretization formulations.
Subtypes define HOW we discretize the governing equations:
- `ContinuumFormulation{Theory}`: Standard FEM for continuum mechanics
- `BeamFormulation{Theory}`: Beam elements (Euler-Bernoulli, Timoshenko)
- `ShellFormulation{Theory}`: Shell elements (Reissner-Mindlin, Kirchhoff)
- `TrussFormulation`: Truss elements
"""
abstract type AbstractFormulation end
"""
AbstractContinuumTheory
Theory variants for continuum formulation.
"""
abstract type AbstractContinuumTheory end
struct FullThreeD <: AbstractContinuumTheory end
struct PlaneStress <: AbstractContinuumTheory end
struct PlaneStrain <: AbstractContinuumTheory end
struct Axisymmetric <: AbstractContinuumTheory end
"""
ContinuumFormulation{Theory} <: AbstractFormulation
Standard continuum mechanics formulation with theory variant.
# Examples
- `ContinuumFormulation{FullThreeD}()`: Full 3D analysis
- `ContinuumFormulation{PlaneStress}()`: 2D plane stress
- `ContinuumFormulation{PlaneStrain}()`: 2D plane strain
"""
struct ContinuumFormulation{Theory<:AbstractContinuumTheory} <: AbstractFormulation end
"""
AbstractBeamTheory
Theory variants for beam formulation.
"""
abstract type AbstractBeamTheory end
struct EulerBernoulli <: AbstractBeamTheory end
struct Timoshenko <: AbstractBeamTheory end
"""
BeamFormulation{Theory} <: AbstractFormulation
Beam element formulation with theory variant.
# Examples
- `BeamFormulation{EulerBernoulli}()`: No shear deformation
- `BeamFormulation{Timoshenko}()`: Includes shear deformation
"""
struct BeamFormulation{Theory<:AbstractBeamTheory} <: AbstractFormulation end
"""
TrussFormulation <: AbstractFormulation
Truss element formulation (axial force only).
"""
struct TrussFormulation <: AbstractFormulation end
# ============================================================================
# Physics Type Hierarchy
# ============================================================================
"""
AbstractPhysics
Abstract base for all physics types.
JuliaFEM recognizes two fundamental categories:
1. Bulk Physics - operates on element sets (domain interiors)
2. Interface Physics - operates on surface pairs (domain boundaries)
"""
abstract type AbstractPhysics end
# ============================================================================
# Constraint Types (placeholder for future implementation)
# ============================================================================
"""
Constraint
Placeholder for internal constraints (rigid body modes, incompressibility, etc.).
To be implemented in future stories.
"""
struct Constraint end
# ============================================================================
# Boundary Conditions
# ============================================================================
"""
DirichletBC
@@ -60,72 +211,252 @@ end
NeumannBC() = NeumannBC(Element[], Vec{3,Float64}[])
# ============================================================================
# Physics Struct (Fully Typed with Type Parameters)
# ============================================================================
"""
Physics{P}
Physics{Formulation<:AbstractFormulation, Field<:AbstractField, Mesh<:AbstractMesh, Material<:AbstractMaterial} <: AbstractPhysics
Container for physics problem with elements and boundary conditions.
Bulk physics operating on element sets.
Type parameter `P` is the physics type (e.g., Elasticity, HeatTransfer).
Represents volumetric phenomena:
- Solid mechanics (elasticity, plasticity, damage)
- Heat transfer
- Fluid dynamics
- Chemical diffusion
Fields:
# Type Parameters (in dispatch priority order)
- `Formulation`: How we discretize - ContinuumFormulation{FullThreeD}, BeamFormulation{Timoshenko}, etc.
- `Field`: What we solve - Displacement{3}, Temperature, etc.
- `Mesh`: Mesh type - AbstractMesh subtype (e.g., Mesh, Mesh{Tet4})
- `Material`: Material type - AbstractMaterial subtype (e.g., LinearElastic, NeoHookean)
# Fields
- `name`: Problem name
- `dimension`: Spatial dimension (1, 2, or 3)
- `properties`: Physics-specific properties (e.g., Elasticity struct)
- `body_elements`: Volume elements with geometry and material
- `mesh`: Reference to Mesh (topology owner - NOT copied!)
- `element_set`: Which elements in mesh this physics applies to
- `field`: Field instance (type Field)
- `formulation`: Formulation instance (type Formulation)
- `material`: Material properties (type Material)
- `constraints`: Optional internal constraints
- `bc_dirichlet`: Dirichlet boundary conditions
- `bc_neumann`: Neumann boundary conditions (surface loads)
# Type Parameter Order Rationale
**Formulation first** enables natural dispatch hierarchy:
```julia
# Most specific: Formulation + Field combination
assemble(::Physics{ContinuumFormulation{FullThreeD}, Displacement{3}, M, Mat}) = ...
assemble(::Physics{ContinuumFormulation{PlaneStress}, Displacement{2}, M, Mat}) = ...
assemble(::Physics{BeamFormulation{Timoshenko}, DisplacementRotation{3}, M, Mat}) = ...
# Generic fallbacks work naturally
assemble(::Physics{ContinuumFormulation, Temperature, M, Mat}) = ... # Any continuum + thermal
assemble(::Physics{Fm, F, M, Mat}) where {Fm,F,M,Mat} = ... # Fully generic
```
# Benefits of Type Parameters
- **Dispatch-optimized order:** Most important types first (formulation, then field)
- **Zero-cost dispatch:** Compiler selects assembly method at compile time
- **Type stability:** All field types known statically
- **Specialization:** Different algorithms per formulation × field combination
- **GPU-ready:** Concrete types enable device-specific optimization
# Design Philosophy
Physics REFERENCES Mesh (does not own it). Multiple Physics can share same Mesh.
Material properties stored in Physics, topology stored in Mesh.
# Example
```julia
physics = Physics(Elasticity, "beam", 3)
add_elements!(physics, elements)
mesh = Mesh("cantilever.inp")
material = LinearElastic(E=210e9, ν=0.3)
physics = Physics(
name = "cantilever",
mesh = mesh,
element_set = :solid,
field = Displacement{3}(),
formulation = ContinuumFormulation{FullThreeD}(),
material = material
)
# Type: Physics{ContinuumFormulation{FullThreeD}, Displacement{3}, typeof(mesh), LinearElastic}
add_dirichlet!(physics, [1,2,3], [1,2,3], 0.0)
sol = solve!(physics)
```
# Dispatch Example
```julia
# Different formulation/field combinations dispatch to specialized methods
physics_continuum_3d = Physics(..., formulation=ContinuumFormulation{FullThreeD}(), field=Displacement{3}())
physics_plane_stress = Physics(..., formulation=ContinuumFormulation{PlaneStress}(), field=Displacement{2}())
physics_beam = Physics(..., formulation=BeamFormulation{Timoshenko}(), field=DisplacementRotation{3}())
physics_thermal = Physics(..., formulation=ContinuumFormulation{FullThreeD}(), field=Temperature())
# Compiler generates specialized code for each formulation × field!
assemble(physics_continuum_3d) # → assemble(::Physics{ContinuumFormulation{FullThreeD}, Displacement{3}, ...})
assemble(physics_plane_stress) # → assemble(::Physics{ContinuumFormulation{PlaneStress}, Displacement{2}, ...})
assemble(physics_beam) # → assemble(::Physics{BeamFormulation{Timoshenko}, DisplacementRotation{3}, ...})
assemble(physics_thermal) # → assemble(::Physics{ContinuumFormulation{FullThreeD}, Temperature, ...})
```
"""
mutable struct Physics{P}
struct Physics{Formulation<:AbstractFormulation,Field<:AbstractField,Mesh<:AbstractMesh,Material<:AbstractMaterial} <: AbstractPhysics
name::String
dimension::Int
properties::P
body_elements::Vector{Element}
bc_dirichlet::DirichletBC
bc_neumann::NeumannBC
mesh::Mesh # Fully typed mesh reference
element_set::Symbol # Which bulk elements
field::Field # What we solve (Displacement{3}, Temperature, etc.)
formulation::Formulation # How we discretize (ContinuumFormulation{...}, etc.)
material::Material # Fully typed material
constraints::Vector{Constraint} # Optional: internal constraints
bc_dirichlet::DirichletBC # Essential boundary conditions
bc_neumann::NeumannBC # Natural boundary conditions
# Inner constructor to ensure type parameters match field instances
function Physics{Formulation,Field,Mesh,Material}(
name::String,
mesh::Mesh,
element_set::Symbol,
field::Field,
formulation::Formulation,
material::Material,
constraints::Vector{Constraint},
bc_dirichlet::DirichletBC,
bc_neumann::NeumannBC
) where {Formulation<:AbstractFormulation,Field<:AbstractField,Mesh<:AbstractMesh,Material<:AbstractMaterial}
new{Formulation,Field,Mesh,Material}(name, mesh, element_set, field, formulation, material,
constraints, bc_dirichlet, bc_neumann)
end
end
"""
Physics(::Type{P}, name::String, dimension::Int) where P
Physics(; name, mesh, element_set, field, formulation, material, constraints=Constraint[])
Create a physics problem of type P.
Create a physics problem referencing a mesh.
Type parameters are automatically inferred from the argument types in dispatch-optimized order.
# Arguments (keyword arguments)
- `name::String`: Problem name
- `mesh`: Mesh reference (topology owner) - type becomes parameter Mesh
- `element_set::Symbol`: Which elements in mesh to use
- `field::AbstractField`: What we solve - type Field inferred
- `formulation::AbstractFormulation`: How we discretize - type Formulation inferred
- `material`: Material properties - type Material inferred
- `constraints`: Optional internal constraints (default: empty)
# Returns
`Physics{Formulation, Field, Mesh, Material}` where types are inferred from arguments
# Example
```julia
physics = Physics(Elasticity, "cantilever", 3)
mesh = Mesh("model.inp")
material = LinearElastic(E=210e9, ν=0.3)
physics = Physics(
name = "cantilever",
mesh = mesh,
element_set = :solid,
field = Displacement{3}(),
formulation = ContinuumFormulation{FullThreeD}(),
material = material
)
# Type: Physics{ContinuumFormulation{FullThreeD}, Displacement{3}, typeof(mesh), LinearElastic}
```
# Type Inference
All type parameters are inferred automatically in dispatch priority order:
- `Formulation = typeof(formulation)` - formulation type (e.g., ContinuumFormulation{FullThreeD})
- `Field = typeof(field)` - field type (e.g., Displacement{3})
- `Mesh = typeof(mesh)` - concrete mesh type
- `Material = typeof(material)` - concrete material type
# Dispatch Benefits
Type parameter order optimized for natural dispatch:
```julia
# Most specific methods dispatch first
assemble(::Physics{ContinuumFormulation{FullThreeD}, Displacement{3}, M, Mat})
# Generic fallbacks work naturally
assemble(::Physics{Fm, F, M, Mat}) where {Fm, F, M, Mat}
```
"""
function Physics(::Type{P}, name::String, dimension::Int) where P
properties = P()
body_elements = Element[]
function Physics(;
name::String,
mesh::M,
element_set::Symbol,
field::F,
formulation::Fm,
material::Mat,
constraints::Vector{Constraint}=Constraint[]
) where {M<:AbstractMesh,Mat<:AbstractMaterial,F<:AbstractField,Fm<:AbstractFormulation}
bc_dirichlet = DirichletBC()
bc_neumann = NeumannBC()
return Physics{P}(name, dimension, properties, body_elements, bc_dirichlet, bc_neumann)
return Physics{Fm,F,M,Mat}(name, mesh, element_set, field, formulation, material,
constraints, bc_dirichlet, bc_neumann)
end
# ============================================================================
# Deprecated API (Compatibility Layer)
# ============================================================================
# Note: Old Physics(::Type{P}, name, dimension) constructor is REMOVED
# The new type signature Physics{M,Mat,F,Fm} is incompatible with the old API
# Users must migrate to: Physics(name=..., mesh=..., field=..., formulation=..., material=...)
"""
add_elements!(physics::Physics, elements::Vector{Element})
Add volume elements to the physics problem.
DEPRECATED: Physics no longer owns elements directly.
# Example
In the new API, Physics references Mesh. Elements are defined in Mesh,
and Physics selects which elements to use via `element_set`.
# Migration
Old API:
```julia
add_elements!(physics, [el1, el2, el3])
physics = Physics(Elasticity, "beam", 3)
add_elements!(physics, elements)
```
New API:
```julia
mesh = elements_to_mesh(elements) # Convert elements to mesh
physics = Physics(
name = "beam",
mesh = mesh,
element_set = :all,
field = Displacement{3}(),
formulation = ContinuumFormulation{FullThreeD}(),
material = extract_material(elements[1])
)
```
This function will be removed in v2.0.
"""
function add_elements!(physics::Physics, elements::Vector{Element})
append!(physics.body_elements, elements)
return nothing
@warn """
add_elements!(physics, elements) is DEPRECATED.
Physics now references Mesh instead of owning elements.
Create a Mesh from elements and pass it to Physics constructor.
Migration:
mesh = elements_to_mesh(elements)
physics = Physics(name=..., mesh=mesh, element_set=:all, ...)
This function will be removed in v2.0.
""" maxlog = 1
# For backward compatibility, we need to somehow add elements to the mesh
# This is hacky but maintains old API temporarily
error("add_elements! no longer supported. Please migrate to new Physics(mesh=...) API.")
end
"""