Profiling on Mac OSX with Saturn

It is always advisable to profile your code before trying to optimize it. It is often most helpful to role your own (using timers & counters), but often a quick and simple tool will help a lot.

For windows I like the very sleepy profiler. On Mac OSX Apple provide the Saturn profiler (See: Saturn profiler user guide).

To demonstrate we can try compiling a small program:

#include <math.h> 
#include <stdio.h> 

#include <saturn.h> //include the saturn profiler

double func1(double x) { //do some maths
    return sin(x)*cos(x); 
} 

double func2(double x) { //do some more maths
    return pow(x,3); 
} 

int main() { 
    double x=0; 
    double z=0; 
    startSaturn(); //being profiling 
    for (x=0;x<100;x+=0.01) {
        z+=func1(x)+func2(x)*tan(x); 
    } 
    stopSaturn(); //end profiling 
    printf("z:%f\n",z); //make sure compiler doesn't throw our computations away
    return 0; 
} 

Now we need to compile it with profiling support:

g++ x.c -finstrument-functions -lSaturn -m32 -O2

Some common problems include:

• 
  
  
  

  Undefined symbols: ___cyg_profile_func_enter
  

  This comes from the -finstrument-functions option : it requires a special hook for each function - this is provided by saturn, so you must link with it.
  
• 
  
  
  

  ld: warning: in /usr/lib/libSaturn.dylib, file is not of required architecture
  Undefined symbols: _startSaturn
  

  Again, either you forgot -lSaturn, or you have remembered it, but are using a 64 bit OS/chip. Specify '-m32' to force 32bit mode.
  

If it all compiled succesfully, then start Saturn and choose 'Saturn', 'Launch Process'. Then select the executable (eg: a.out) in the dialog box.

Press OK, and Saturn will run and profile your program, and generate a folder with the profiler output data. (eg: Saturn_profile_a.out.000)

You can then select the data file to view the output, and Saturn will display a call graph and the amount of time spent in each function. Now the fun of optimizing can begin. Enjoy!