If Intel is using floating point math shortcuts you can replicate it with -Ofast when using gcc.
It goes without saying that you should use -O3 (or -O2 for some rare cases) otherwise. I am mentioning it just in case because 2.5x slower sounds so exotic to me that the first intuition is that you're omitting important optimization flags when using GCC. GCC was faster than Intel on everything I tried in the past.
It goes without saying that you should use -O3 (or -O2 for some rare cases) otherwise. I am mentioning it just in case because 2.5x slower sounds so exotic to me that the first intuition is that you're omitting important optimization flags when using GCC. GCC was faster than Intel on everything I tried in the past.