SVD computing different result in Matlab and OpenCV

Question

I wonder why there is sign difference in result for SVD computing in Matlab and OpenCV. I input the same matrix

          3.65E+06  -2.09E+06   0
 YY =    -         


        

Answer 1

The results of the SVD need not be unique. For example, I = UIV' for any unitary V = U. The example you give above in particular is rank deficient, so there is no reason to expect uniqueness.