Dear Sir/Madam: I am sorry I met a problem when I used gcc to compile my C program and ran the executables on servers. I compiled my C program with the following two different ways with different options. gcc -m32 -O3 -DNDEBUG -fno-strict-aliasing -static ?lm gcc -m32 ?O3 ?lm My problem is that the two executables obtained by using the above two ways have the same performance on some inputs but have different performance on other inputs. I am sorry I do not know whether executables with different options should always have the same performance if the parameters are the same when executing these two executables. If two executables with different options should always have the same performance, the different performance of the two executables of my C program means there are bugs in this program? Thank you for your time and help. Yours sincerely, Wanxia Wei