@code_warntype with StaticArrays

New to Julia
1

I am initializing a MVector and MMatrix from StaticArrays inside a function as follows

function test(v::Vector{T}) where{T<:Real}
    n = length(v)
    myvec = MVector{n, T}(undef)
    mymat = MMatrix{n, n, T}(undef)

...

end

If I do

v=[1.0, 2.0]
@code_warntype test(v)

I get output that begins

Static Parameters
  T = Float64
Arguments
  #self#::Core.Const(test)
  v::Vector{Float64}
Locals
  mymat::Any
  myvec::MArray{_A, Float64, 1} where _A<:Tuple
  n::Int64
Body::Any

What am I doing wrong when I initialize my vector and matrix? Thanks.

2

StaticArrays are type-inferred if the size is known at compile time, not runtime. In your case, n is only known at run-time, so the type can’t be inferred. Moreover, in the MMatrix constructor, you need to specify the fourth parameter, which is the length of the array n^2.

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