### amiralisalimi's blog

By amiralisalimi, history, 2 months ago, ,

I am facing a really weird fast execution time on Codeforces on submission 75468775. On test #6, the code runs for 1153 ms on Codeforces servers, but when I run it on my own computer, it takes me 5682 ms to run! Yes there is difference on hardware of course, but it runs about 5 times faster on Codeforces! I am wondering if there is any optimization on Codeforces servers or compile instructions which makes it run as fast as this?

UPD: That is actually because of -O2 compile flag. Never knew it affects the running time as much as making it run 5 times faster.

• +9

 » 2 months ago, # |   +12 I guess the reason is compiler flag to optimize code. Possible ReasonYour solutions are compiled with the command line g++ -static -DONLINE_JUDGE -Wl,--stack=268435456 -O2 -std=c++17 program.cpp.Link to SourceMaybe I am wrong. But let us find out the answer.
•  » » 2 months ago, # ^ |   0 Yes, Yes. You are right. Actually this is because of -O2 flag. I didn't know this flag is effective like this! I should have probably tested running the code with Codeforces compile flags before posting the blog.
 » 2 months ago, # |   0 Auto comment: topic has been updated by amiralisalimi (previous revision, new revision, compare).