You have a good criticism on my #1. I should drop "ask the expert" part but still maintain that when writing numerical computation software checking for compile

You have a good criticism on my #1. I should drop "ask the expert" part but still maintain that when writing numerical computation software checking for compile flags is a reasonable request. Leave code as is, but still try -O3 / -Ofast. At this point it is not the language expertise, but knowing about your tools.