Distributed hierarchical matrix

When calling assemble_hmatrix, the keyword argument distributed can be set to true in order to generate a DHMatrix object. The main difference between an HMatrix and a DHMatrix is that the leaves of a DHMatrix represent a remote reference to an HMatrix possibly stored on a different worker.

In order to use the distributed capabilities, you must first add the Distributed package and add some workers:

using Distributed
addprocs(4)

You can then load the HMatrices package everywhere, and proceed as before:

@everywhere using HMatrices
using LinearAlgebra, StaticArrays
const Point3D = SVector{3,Float64}
m = 10_000
X = Y = [Point3D(sin(θ)cos(ϕ),sin(θ)*sin(ϕ),cos(θ)) for (θ,ϕ) in zip(π*rand(m),2π*rand(m))]
const μ = 5
function G(x,y)
    r = x-y
    d = norm(r) + 1e-10
    1/(8π*μ) * (1/d*I + r*transpose(r)/d^3)
end
K = KernelMatrix(G,X,Y)
H = assemble_hmatrix(K;atol=1e-4,distributed=true,threads=false)

TODO: add an interactive notebook example