MAJOR PERFORMANCE REFACTORING:
1. Shape functions return tuples instead of allocating vectors:
- eval_basis!(): Returns NTuple{N,T} directly (zero allocations)
- eval_dbasis!(): Returns NTuple{N,Vec{D}} directly (zero allocations)
- API boundary (get_basis/get_dbasis) still returns vectors for compat
2. Element is now immutable with compile-time known structure:
- connectivity: Vector{UInt} → NTuple{N,UInt}
- integration_points: Vector{IP} → NTuple{NIP,IP}
- Element{N,NIP,M,B} parametrized by connectivity/IP count
- Changed from 'mutable struct' to 'struct'
3. Helper function for immutability:
- with_integration_points(element, ips) returns new element
- get_integration_points() returns tuple directly
Benefits:
- Zero allocations in hot paths (basis evaluation)
- Compile-time sizes enable better optimization
- Type stability improvements
- Stack allocation instead of heap
Breaking changes:
- Element.connectivity is now tuple (use collect() for vector)
- Element is immutable (use with_integration_points for updates)
Tests: All 157 tests passing
Major architectural decision: Use Tensors.jl consistently everywhere
for geometric vectors, integration points, and coordinates.
Changes to src/elements/elements.jl:
- get_basis(): Convert ip to Vec, use Vector (not Matrix) for eval_basis!
- get_dbasis(): Convert ip to Vec
- jacobian evaluation: Convert geometry and ip.coords to Vec properly
- Handle both raw coordinates (Tuple) and IP struct transparently
New Tutorial 3: Numerical Integration and Jacobian (49 tests)
- Integration point structure and weights
- Jacobian determinant and matrix evaluation
- Numerical integration (constant, linear, quadratic functions)
- Multiple element types (Quad4, Seg2, Tri3)
Tests: 107 → 156 passing (49 new)
Runtime: ~7 seconds
Closes architectural standardization on Tensors.jl.
Related to Issue #250 (merge conflict resolution).
Why Tensors.jl:
- Type stability (100× performance vs Dict-based)
- Material science compatibility (stress tensors)
- Zero-cost abstractions
- Consistent API across all geometric calculations
Current state discovery:
- Element basis function evaluation broken (eval_basis! signature mismatch)
- Field interpolation at integration points broken (same root cause)
- Jacobian evaluation at integration points broken
- These are fundamental API issues affecting multiple test paths
Impact:
- Tutorial 3 (basis functions) deferred until API fixed
- Affects any code trying to evaluate fields at integration points
- Related to Quad4 assembly issues discovered in Tutorial 4
Working tutorials (107/107 tests passing):
- Tutorial 1: Element creation (5 tests)
- Tutorial 2: Gmsh mesh reading (72 tests)
- Tutorial 4: 1-element validation (35 tests)
Next: Focus on tutorials using working APIs only
Educational validation test for Issue #265 use case (JuliaFEM as reference).
Covers:
- Element creation and connectivity
- Field assignment (geometry, material properties)
- Field retrieval with function call syntax
- Hand-calculated constitutive matrix for plane stress
- Geometry validation (dimensions, center, area)
- Material property validation (physical ranges)
Note: Defers stiffness matrix assembly to future work due to current
Quad4 assembly issues. Focus is on element setup validation that
other FEM developers can use as reference.
Tutorial series now: 107/107 tests passing
- Tutorial 1: Creating elements (5 tests)
- Tutorial 2: Gmsh mesh reading (72 tests)
- Tutorial 4: 1-element validation (35 tests - done before Tutorial 3)
Implement testing philosophy (see docs/TESTING_PHILOSOPHY.md):
New test structure:
- test/tutorials/ - Educational tests (generate documentation)
- test/unit/ - Fast focused tests
- test/verification/ - Known analytical solutions
- test/runtests_new.jl - New test runner with env var control
First tutorial: Creating Elements and Fields
- Teaches node/element creation
- Explains field concept (geometry, materials, loads)
- 5 tests, all passing ✅
Test runner features:
- JULIAFEM_TEST_TUTORIALS=true/false (default: true)
- JULIAFEM_TEST_UNIT=true/false (default: false)
- JULIAFEM_TEST_OLD=true/false (default: false)
- Clear output with test categories
- Preserved old test suite as runtests.jl.old
Results: 5/5 tests passing in <2 seconds
Next: Write 2-3 more fundamental tutorials (mesh reading, 1D elasticity)
Jukka Aho