Question

我正在尝试调用SVM.train()计算出的训练数据上的HOGDescriptor。

HOGDescriptor hog = HOGDescriptor();

vector<Mat> gradients;
compute(trainingImgs, gradients);
cout << "descriptors generated: " << gradients[0].size() << endl;


vector<int> labels;
labels.assign(gradients.size(), 1);

//set up SVM properties
Ptr<SVM> svm = SVM::create();
svm->setCoef0(0.0);
svm->setDegree(3);
svm->setTermCriteria(TermCriteria(TermCriteria::MAX_ITER + TermCriteria::EPS, 1000, 1e-3));
svm->setGamma(0);
svm->setKernel(SVM::LINEAR);
svm->setNu(0.5);
svm->setP(0.1); // for EPSILON_SVR, epsilon in loss function?
svm->setC(0.01); // From paper, soft classifier
svm->setType(SVM::EPS_SVR); // C_SVC; // EPSILON_SVR; // may be also NU_SVR; // do regression task


//max length of the descriptor vectors, I am a maths programmer now
int n = gradients[0].rows;
Mat trainData = Mat(gradients.size(), gradients[0].rows, CV_32FC1);
cout << "trainData size: " << trainData.rows << "x" << trainData.cols << endl;


Mat tmp(1, n, CV_32FC1);
for (int i = 0; i < gradients.size(); i++)
{
    //this would probably be better as a single operation butfuckit
    transpose(gradients[i], tmp);
    tmp.copyTo(trainData.row((int)i));
    cout << "arbitrary item in " << i << "th Mat: " << trainData.at<float>(i, 93426) << endl;
}
cout << "copy operation complete" << endl;

//actually train the SVM
svm->train(trainData, ROW_SAMPLE, labels);
cout << "training complete" << endl;

计算定义为

void compute(const vector<Mat> &imgs, vector<Mat>& gradList)
{
    HOGDescriptor hog;
    vector<float> descriptors;
    for (int i = 0; i < imgs.size(); i++)
    {
        hog.compute(imgs[i], descriptors, Size(8, 8), Size(0, 0));
        gradList.push_back(Mat(descriptors).clone());
    }
}

和trainingImgs是5张测试训练图像（全部相同）中的vector<Mat>。

问题在于svm->train()调用会生成Error: Assertion failed (sv_count != 0)。我可以找到的关于此错误的唯一信息是，它可能意味着训练数据为空，但看起来似乎什么都不是，只是打印到控制台上之后。

从source code看来，sv_count是其对应的_alpha值大于0的样本数，但是我无法跟踪生成_alpha值的位置

我正在使用Visual Studio 2019中的CMake构建OpenCV(4.1.2-dev)。

感谢您的帮助。

OpenCV SVM训练断言失败（sv_count！= 0）

0 个答案: