svd value different between matlab 2011b and 2012b

Question

i try to implement the same matrix F to the svd function on both versions of matlab. However, i found out that sign of U and V matrix from both solutions are opposite. May i know which versions of MATLAB provide a better or more accurate answer? or actually both answers are correct?

Answer 1

The singular value decomposition of a matrix is only defined up to a sign, so the signs of U and V are arbitrary, and both answers are correct. Whichever signs MATLAB produces, it should still be the case that F = U*S*V, so U and V constitute a correct singular value decomposition of F. (Note "a", not "the").

You shouldn't rely on MATLAB producing particular signs, and it may vary from version to version.