I tried to compile the following code with g++ 3.3.3 (g++ -m64 -O3): #include <vector> #include <algorithm> #include <ctime> #include <cstdio> using namespace std; #define BENCH_TYPE double int main() {     vector<BENCH_TYPE> v;     printf("Generating 10M elements\n");     for (int i = 0; i < 10000000; i++)                 v.push_back((BENCH_TYPE)(rand()*0.5 + rand()));         printf("generated\nSorting...\n");         clock_t start = clock();         sort(v.begin(), v.end());         clock_t end = clock();         printf("%f\n", (end - start)/((double)CLOCKS_PER_SEC));         return 0; } The resulting executable doesn't finish in a minute or so and I have to break its execution. The funny thing is that the same code compiled with g++ -m64 -O0 finishes in 8 sec or so. What's going on? Any ideas? I have Suse 9.1 x86_64 with the latest updates of all installed packages. I wouldn't bother a lot about this test code, if it wasn't for a more serious problem: I downloaded and installed the latest x86_64 build of the kernel 2.6.5-7.145-default and the nVidia graphics driver stopped working. I manually downloaded the latest driver from the nVidia web site: NVIDIA-Linux-x86_64-1.0-6629-pkg2.run and installed it and when I started X it was painfully slow and I had to kill it. I don't know if the two problems are related. I would appreciate any help on any of them. Thanks a lot.