def Cuvature_Condition(pg_next,c2,pg_initial):
    """
    :param pg_next: inner product of step direction, p, with the gradient after stepping, g_next
    :param c2: 0<c1<c2<1
    :param pg_initial: inner product of step direction, p, with the gradient before stepping, g_initial
    :return:True if condition is satisfied
    """
    return  (-pg_next <= -c2*pg_initial)