Pure Fdp gaussian mechanism doesn't work under composition of multiple rounds

Computing the get_fDP(delta) for a gaussian mechanism with pure Fdp works fine, but trying to compose the pure-fdp gaussian mechanism for several rounds, the function get_approxDP(delta) always returns inf as the result of composition.

Fdp seems not to work under Composition or AmplificationBySampling

def compute_amplified_fl_privacy(num_rounds=60, noise_multiplier=20, num_users=500, users_per_round=100):
    gm1 = GaussianMechanism(sigma=noise_multiplier, RDP_off=True, approxDP_off=True, fdp_off=False)

    compose = Composition()
    num_rounds = [num_rounds]
    q = users_per_round / num_users
    delta = num_users ** (-1)

    composed_fdp = compose([gm1], num_rounds)

    composed_fdp_eps = composed_fdp.get_fDP(delta)
    composed_fdp_approxdp = composed_fdp.get_approxDP(delta)

    mechanism_fdp_eps = gm1.get_fDP(delta)
    mechanism_fdp_approxdp = gm1.get_approxDP(delta)
    print('---------------------------------------------------')
    print('composed fdp eps = ', composed_fdp_eps, ', at delta = ', delta)
    print('composed fdp eps_approxdp = ', composed_fdp_approxdp, ', at delta = ', delta)

    print('mechanism fdp eps = ', mechanism_fdp_eps, ', at delta = ', delta)
    print('mechanism fdp approxdp = ', mechanism_fdp_approxdp, ', at delta = ', delta)

def main():
    compute_amplified_fl_privacy(num_rounds=60, noise_multiplier=20, num_users=500, users_per_round=100)

if __name__ == '__main__':
    main()
    print('DONE')

yuxiangw / autodp

Pure Fdp gaussian mechanism doesn't work under composition of multiple rounds #15