为什么opencv SVM预测相同的对象结果在2次训练后有所不同？

Question

我在这里有以下代码。我想问的是为什么opencv SVM预测2次训练后相同的对象结果是不同的？有任何解决方案可以结合2次训练结果吗？任何建议将被认真考虑。抱歉我的英语不好。

int main(int argc, char **argv){

    // Set up SVM's parameters
    CvSVMParams params;
    params.svm_type    = CvSVM::C_SVC;
    params.kernel_type = CvSVM::LINEAR;
    params.term_crit   = cvTermCriteria(CV_TERMCRIT_ITER, 100, 1e-6);

    CvSVM SVM;
    int idx, idx2;

    // Set up test sample
    Mat test = Mat(1, 2, CV_32FC1);
    test.at<float>(0,0) = 1;
    test.at<float>(0,1) = 1;

    // Set up 1st training data
    float labels[4] = {0, 1, 2, 3};
    Mat labelsMat(4, 1, CV_32FC1, labels);

    float trainingData[4][2] = { {0, 0}, {1, 1}, {2, 2}, {3, 3} };
    Mat trainingDataMat(4, 2, CV_32FC1, trainingData);
    SVM.train(trainingDataMat, labelsMat, Mat(), Mat(), params);

    // Predict sample
    idx = SVM.predict(test);

    // Set up 2nd training data
    float labels2[4] = {4, 5, 6, 7};
    Mat labelsMat2(4, 1, CV_32FC1, labels);

    float trainingData2[4][2] = { {4, 4}, {5, 5}, {6, 6}, {7, 7} };
    Mat trainingDataMat2(4, 2, CV_32FC1, trainingData2);
    SVM.train(trainingDataMat2, labelsMat2, Mat(), Mat(), params);

    // Predict sample
    idx2 = SVM.predict(test);

    printf("idx [%d] idx2 [%d]\n", idx, idx2);
    waitKey(0);
    return 1;
}

以上代码输出为idx [1] idx2 [0]。为什么？