def METHOD_NAME(steps, t, dt):
    rho = nodes1.massDensity()
    rhoMin = rho.min()
    rhoMax = rho.max()
    fluc = abs(rhoMin/rhoMax - 1.0)
    print("rho bounds : [%g, %g], variation %g" % (rhoMin, rhoMax, fluc))
    if fluc > tol:
        dumpPhysicsState(integrator,
                         baseFileName = "periodic_boundary_2d",
                         fieldLists = [db.fluidMass, db.fluidMassDensity, db.fluidVelocity, db.fluidHfield],
                         currentTime = t,
                         currentCycle = steps,
                         dumpGhosts = False)
        raise ValueError("rho fluctuation outside bounds")
    return