[Development] What kind of airplane we want to build?

Kevin Kofler kevin.kofler at chello.at
Sun Jan 24 03:11:26 CET 2016


Bogdan Vatra wrote:
> gcc -O2 and -O3 gives the worst/random/surprising results. On the other
> hand, clang (to my HUGE surprise) gives the most consistent results.

That doesn't surprise me all that much. I've seen REALLY strange 
benchmarking results from GCC-generated code. In particular, I had a program 
where I was trying to benchmark the win from parallelizing the code, and I 
found that the mere fact of adding -pthreads to the compiler flags, without 
actually doing ANY parallelization, was making the code FASTER. (If 
anything, it is expected to run slower, because of additional locks.)

        Kevin Kofler




More information about the Development mailing list