AIX xlC implementation of STL significantly slower than other platforms?

Question

Something that takes 1 second to run on Linux takes 45 seconds to run on AIX. I haven't dug directly into that code but as a test grabbed a small application that does very little from another SO question:

int main ( int argc, char **argv)
{
int i = 0;
std::vector<int> vec;
vec.push_back(6);
vec.push_back(-17);
vec.push_back(12);

for (i=0;i<100000;i++)
   vec.push_back(i);

vec.erase(vec.begin() + 1);
return 0;
}

I have an old compiler (7.0.0.10) and I cannot belive how much slower the code runs vs. the same code on g++ 4.2.

Has anyone seen this before? It would take some work to upgrade the compiler. The sample code is about 20 times slower (real time) on a system with almost no load.

Update Reqested Box Specifications:

    Number Of Processors: 8
    Processor Clock Speed: 3504 MHz
    CPU Type: 64-bit
    Kernel Type: 64-bit
    Memory Size: 63232 MB
    Good Memory Size: 63232 MB
    Platform Firmware level: EM340_041
    Firmware Version: IBM,EM340_041
    Console Login: enable
    Auto Restart: true
    Full Core: true

Output on AIX:

real    0m0.52s
user    0m0.51s
sys     0m0.00s

Output on Linux:

 0.00s real     0.01s user     0.00s system

Answer 1

A couple of suggestions to narrow down the problem:

• Use time on your program and look at the system/user times, not elapsed time. That will give you a better indication.
• put a system("date") before each of the three initial push_back statements, before the for loop, before the erase and before the return. This will show which operation is causing the problem.
• Tell us what hardware you're running on as well. You may have a 286-class pSeries.

Then get back to us with the hard data and we can help out some more.

Answer 2

I suspect a suboptimal memory allocation strategy. What happens if you add

vec.reserve(10000);

before the for-loop?

Answer 3

Either there is something seriously wrong with your setup, or you haven't posted the real code. The folowing executes almost instantly on a very old 900Mhz Pentium laptop with little memory:

#include <iostream>
#include <vector>
#include <ctime>
using namespace std;;

int main ( int argc, char **argv) {

    time_t now1 = time(0);
    std::vector<int> vec;
    vec.push_back(6);
    vec.push_back(-17);
    vec.push_back(12);
    for ( int i = 0; i<10000; i++) {
      vec.push_back(i);
    }

    time_t now2 = time(0);
    vec.erase(vec.begin() + 1);

    time_t now3 = time(0);
    cout << (now2 - now1) << " " << (now3 - now2)  << endl;
}

Please run this code through both compilers and report the numbers it outputs.