PSD.py 文件源码

def vec_to_X(v_X):
    n = int(math.sqrt(2 * len(v_X)))
    if len(v_X) != n * (n + 1) / 2:
        raise ValueError(
            "v_X is not the right shape for a vectorized lower triangular matrix. Tried to turn vector of size {} into matrix with width {} ".format(len(v_X), n))
    Y = np.zeros((n, n))
    Y[np.tri(n, dtype=np.bool).T] = v_X
    return Y + np.triu(Y, 1).T