def send_data_to_gpu(simulation):
    """
    Send the simulation data to the GPU.
    Calls the functions of the particle and field package
    that send the data to the GPU.

    Parameters :
    ------------
    simulation : object
        A simulation object that contains the particle
        (ptcl) and field object (fld)
    """
    for species in simulation.ptcl:
        if species.use_cuda:
            species.send_particles_to_gpu()
    simulation.fld.send_fields_to_gpu()
