https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83497
Pat Haugen <pthaugen at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|WAITING |RESOLVED Resolution|--- |INVALID --- Comment #5 from Pat Haugen <pthaugen at gcc dot gnu.org> --- I have confirmed that this is indeed just a precision difference due to a different mix and order of instructions for the computation in the RESID loop, valid reassociation with -ffast-math. The difference is then compounded as the benchmark iterates over the values. The specdiff command for mgrid specifies an absolute tolerance of "-a 1e-12" and uses the absolute difference when seeing if two values are within the specified tolerance. In this case they were not.