functions.py 文件源码

def f2(x,returntype=LINALGMAXFLOAT):
    '''
    Second derivative of sigmoid

    (q - p) p q
    '''
    x = np.float128(x)
    logp = -np.logaddexp(ZERO128,-x)
    logq = -np.logaddexp(ZERO128, x)
    p  = np.exp(np.minimum(F128EMAX,logp))
    q  = np.exp(np.minimum(F128EMAX,logq))
    return returntype((q-p)*q*p);