SURF_GPU matching with FLANN

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Hi! How I convert the vector (std::vector<float>) of descriptors obtained with cv::gpu::SURF_GPU (through the downloadDescriptors(...) function) into a matrix (cv::Mat) of descriptors to use with the FLANN matcher (cv::FlannBasedMatcher)?

Have any sense what I'm trying to do? That is, there are better alternatives to match SURF descriptors taking advantage of the GPU?

Thanks!