How to convert a matrix of stl vectors to matrix of 2d arrays

[bjb414]

I'm using CUDA but it seems i can't use or pass STL vectors as parameters so i need to convert those matrix of vectors

std::vector< std::vector<float> > some_matrix;

to

float **f;

i tried to use the memcpy function but for some reason it does't work as expect, if i try to copy the contents, some of the values in the original matrix are change for garbage.