SEAL：多次乘法后解密不正确

Question

我对2个双精度值进行了加密，对乘法进行了循环，发现第三次乘法的结果错误，并且第四次乘法被中止。我的代码是否存在问题，或者印章不支持多次乘法？

void testMul()
{
    EncryptionParameters parms(scheme_type::CKKS);  
    parms.set_poly_modulus_degree(8192);
    parms.set_coeff_modulus({DefaultParams::small_mods_40bit(0), DefaultParams::small_mods_40bit(1),DefaultParams::small_mods_40bit(2), DefaultParams::small_mods_40bit(3) });

    auto context = SEALContext::Create(parms);
    KeyGenerator keygen(context);
    auto public_key = keygen.public_key();
    auto secret_key = keygen.secret_key();
    auto relin_keys = keygen.relin_keys(DefaultParams::dbc_max());
    Encryptor encryptor(context, public_key);
    Evaluator evaluator(context);
    Decryptor decryptor(context, secret_key);
    CKKSEncoder encoder(context);

    auto scale = static_cast<double>(parms.coeff_modulus().back().value());
    double d1 = 3, d2 = 2, dResult, dTemp;
    dResult = d2;
    Plaintext plain_coeff1, plain_coeff2,plain_result;
    encoder.encode(d1, scale, plain_coeff1);
    encoder.encode(d2, scale, plain_coeff2);

    Ciphertext encrypted_x1, encrypted_x2;
    encryptor.encrypt(plain_coeff1, encrypted_x1);
    encryptor.encrypt(plain_coeff2, encrypted_x2);

    for (int i = 0; i < 10; i++)
    {
        dTemp = dResult;
        encrypted_x2.scale() = encrypted_x1.scale();
        evaluator.mod_switch_to_inplace(encrypted_x1, encrypted_x2.parms_id());
        evaluator.multiply_inplace(encrypted_x2, encrypted_x1);
        evaluator.relinearize_inplace(encrypted_x2, relin_keys);             
        evaluator.rescale_to_next_inplace(encrypted_x2);

        decryptor.decrypt(encrypted_x2, plain_result);
        vector<double> result;
        encoder.decode(plain_result, result);
        dResult = result[0];
        cout << dTemp << " * " << d1 <<  " =" << dResult << endl;

    } 
}

output
{
        2 * 3 =6
        6 * 3 =18
        18 * 3 =-0.000702552
        terminate called after throwing an instance of 'std::invalid_argument'
        what():  scale out of bounds
        Aborted (core dumped)

}