Floating point computations on computers may behave differently than one might expect. Every software developer should be aware of these since computed results may be off by orders of magnitude in the worst case.
My first encounter with this subject was when I implemented the algorithms for the inpainting mask optimization.
Recently I investigated the accuracy of QR decompositions that use Gram-Schmidt for the orthogonalisation process. The findings have been posted on this site in a series of posts in 2020.