https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79720
--- Comment #6 from Dominique d'Humieres <dominiq at lps dot ens.fr> --- > but gcc 6 and 7 fail. So does 4.8, 4.9, and 5. IMO this PR should be closed as invalid: the assumption that the roundoff errors don't depend on the optimization level is wrong.
