Reverse engineering history pattern length in branch predictor - reverse-engineering

Question

I'm trying to find the length of the history pattern in the branch predictor of my computer's processor. I generated variable length array of bits and have if conditions based on the value of the bit. I will then plot the run time of different execution of the function and search for the knee in the graph. but I don't see any such point in the graph. What am I doing wrong? Any idea?
Here is my code:
vector<int> randomArr(int n)
{
vector<int> arr (n);
for ( int i=0; i <n; i++){
arr[i] = rand() % 2;
}
return arr;
}
int branchy(vector<int> & arr){
int a = 0 ;
int b = 0 ;
for ( int i = 0 ; i < arr.size() ; i++ ) {
if ( arr[i] == 0)
a++;
else
b++;
}
return a^b;
}
int main() {
long int iterations = 100000;
int start_s;
int stop_s;
ofstream runtimesFile;
runtimesFile.open("runtimesFile.txt");
for (int j=0; j <iterations ; j++){
vector<int> arr = randomArr(j);
start_s=clock();
branchy(arr);
stop_s=clock();
runtimesFile<< to_string(stop_s-start_s)<<"\n";
}
runtimesFile.close();
return 0;
}