G++ optimization beyond -O3/-Ofast

Question

The Problem

We have a mid-sized program for a simulation task, that we need to optimize. We have already done our best optimizing the source to the limi

Answer 1

huh, then final thing you may try: ACOVEA project: Analysis of Compiler Optimizations via an Evolutionary Algorithm -- as obvious from the description, it tries a genetic algorithm to pick the best compiler options for your project (doing compilation maaany times and check for timing, giving a feedback to the algorithm :) -- but results could be impressive! :)

Answer 2

with gcc intel turn of / implement -fno-gcse (works well on gfortran) and -fno-guess-branch-prbability (default in gfortran)