How do I convert an cv::Mat to float pointer?

I want to represent the matrix of `cv::SIFT` descriptors `cv::Mat descriptors` as `float*`. This is because I want to use [GMM from VLFeat][1] (if you any better solution, please let me know). This is the code that I came up with: if(!prova.isContinous()){ std::err<<"Descriptor matrix not continuous!"<(3,3) << 0.1, 0.3, 2.1, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8); And print the values: for(int i=0;i