Dispatch size static array: looking for good examples

Internals & Design
1

Given a struct defining an element, e.g.,

using StaticArrays

const Point2D = SVector{2,Float64};

# struct to hold a single mesh element
struct Element
  p1::Point2D                   # coordinates first node 
  p2::Point2D                   # coordinates second node 
  p3::Point2D                   # coordinates third node     
  e1::Int64                     # global index first node
  e2::Int64                     # global index second node
  e3::Int64                     # global index third node
  Emat::MMatrix{3,3,Float64, 9} # matrix of basis function coefficients 
  area::Float64                 # area of the element 
end

and given a mesh as an array of such elements, e.g.,

# struct to hold entire mesh
struct Mesh
  nnodes::Int64               # number of nodes 
  nelems::Int64               # number of elements
  Elements::Array{Element,1}  # list of Elements 
  bndNodeIds::Vector{Int64}   # indices of nodes where Dirichlet bc are applied  
  dofPerElem::Int64           # number of dofs per element 
end

I wish to implement the method

stiffmat(mesh)

Q1: I am considering using dispatch on the length of the static array, see e.g. API · StaticArrays.jl . More examples of this method would be wonderful to see.

Q2: how to implement dispatch on length of the static array Point2D such that the same signature works for elements in line segments 1D, 2D and 3D.

A partial answer is given for linear elements only is given in MinFEM.jl/src/fem.jl at master · MinFEM/MinFEM.jl · GitHub .

Is it common practice to inquire the length on mesh.Element[1].p1 in the signature of the function stiffmat() for instance?

Q3: how to implement dispatch on the type of element such that the same signature works for linear and quadratic elements in 1D for instance.

1 Like
2

The function stiffmat() will loop over the elements.

One solution is therefore to stack the points (p1, p2 and p3) as collumns a of static array of size ndim by number-of-points, and perform dispatch of a size of this static array.