Setindex! for sparse arrays

[ziolai]

The question that follows was raised earlier at e.g. performance-enhancement-for-setindex-for-sparse-array.

I remain confused regarding the use of sparse(Is,Js,As,[n,n]). profview shows that computation time is spend in setindex!.

The code that follows

"""
    genLocStiffMat(element::Element)

Generates local stiffness matrix for single linear triangular element. 
"""
function genLocStiffMat(element::Element)
    v    = SVector(element.e1, element.e2, element.e3)   
    Emat = copy(element.Emat) 
    area = element.area 
    reluctivity = element.physics.reluctivity
    Iloc = SVector{9}(v[i] for j=1:3, i=1:3)
    Jloc = SVector{9}(v[i] for i=1:3, j=1:3) 
    Emat[3,:] .= 0.;  
    Amat = SMatrix{3,3}(area*reluctivity*(transpose(Emat)*Emat))
    Aloc = vec(Amat)
    return Iloc, Jloc, Aloc
end

"""
    genStiffMat(mesh::Mesh)

Generates global stiffness matrix on mesh of linear triangular elements. 
"""
function genStiffMat(mesh::Mesh)
 
    #..recover number of elements  
    nnodes      = mesh.nnodes 
    nelems      = mesh.nelems 
    dofPerElem  = mesh.dofPerElem
    dofPerElem2 = dofPerElem^2

    #..set range vector 
    irng = SVector{9}(1:9)

    #..preallocate the memory for local matrix contributions 
    Avalues = zeros(Float64,dofPerElem2*nelems)
    I = zeros(Int64,length(Avalues))
    J = zeros(Int64,length(Avalues))

    #..loop over number of elements..
    for element in mesh.Elements 
        Iloc, Jloc, Aloc = genLocStiffMat(element) 
        I[irng] .= Iloc 
        J[irng] .= Jloc 
        Avalues[irng] .= Aloc   
        irng = irng.+dofPerElem2
    end
 
    #..form sparse matrix        
    A = sparse(I,J,Avalues,nnodes,nnodes)
   
    return A; 
end

indeed has a Profvview as shown below.

Thanks.