Permutation initializer

[MartinuzziFrancesco]

Description

Random columns permutations of the identity matrix, rescaled by a certain factor. This can be generalized using our infrastructure to also be full random. Ref1, and ref2 (mentioned as the original source in ref1)

Implementation

function permutation_init(rng::AbstractRNG, ::Type{T}, dims::Integer...;
        weight=T(0.1), return_sparse = false, permutation_matrix = nothing, 
        kwargs...) where {T <: Number}
    throw_sparse_error(return_sparse)
    reservoir_matrix = DeviceAgnostic.zeros(rng, T, dims...)
    self_loop!(rng, reservoir_matrix, weight; kwargs...)
    permuted_matrix = permute_matrix(reservoir_matrix, permutation_matrix)
    return return_init_as(Val(return_sparse), permuted_matrix)
end

function apply_permutation!(reservoir_matrix::AbstractMatrix, permutation_matrix::AbstractMatrix) # Union(nothing)
    if permutation_matrix == nothing
        perm_array = randperm(size(reservoir_matrix, 1))
        permutation_matrix = create_permutation_matrix(perm_array)
    end
    return reservoir_matrix * permutation_matrix
end

function create_permutation_matrix(p::AbstractVector{Int})
    n = length(p)
    P = zeros(Float64, n, n)
    for i in 1:n
        P[i, p[i]] = 1.0
    end
    return P
end