[wycy]

Using -O3 was resulting in correctness problems in my work codebase in the past. Nowadays the compiler (ifort) crashes when using -O3 for some reason.

[qweqwe14]

> Using -O3 was resulting in correctness problems

Likely because your codebase had UB in it that didn't show itself until a certain optimization level. The solution is to fix all instances of UB. See my comment above.

[wycy]

I believe in our case it was a compiler bug, because it only happened for a few versions of ifort and was eventually fixed. But it scared us off from using -O3.