The calculation of axial currents (Algorithm 1 in https://doi.org/10.3389/fninf.2018.00092) is linear, that is, the I = A*V_1 + B*V_2 + C*... where the coefficients A, B, C, ... are computed from the corresponding compartment axial resistivity. The calculation of axial currents from membrane voltages can be reformulated as I = MV where V is a matrix with all voltages, M a sparse matrix with the corresponding coefficients that can be computed once. The calculation of axial currents can then be computed very fast without explicit for loops.

@solveignaess, does this sound feasible?