Pfthb

I'm relatively new to Java programming, and I'm running into an issue calculating the amount of time it takes for a function to run.

First some background - I've got a lot of experience with Python, and I'm trying to recreate the functionality of the Jupyter Notebook/Lab %%timeit function, if you're familiar with that. Here's a pic of it in action (sorry, not enough karma to embed yet):

Snip of Jupyter %%timeit

What it does is run the contents of the cell (in this case a recursive function) either 1k, 10k, or 100k times, and give you the average run time of the function, and the standard deviation.

My first implementation (using the same recursive function) used System.nanoTime():

public static void main(String args) 

 long t1, t2, diff;
 long times = new long[1000];
 int t;
 for (int i=0; i< 1000; i++) 

 t1 = System.nanoTime();
 t = triangle(20);
 t2 = System.nanoTime();

 diff = t2-t1;
 System.out.println(diff);
 times[i] = diff;
 

 long total = 0;
 for (int j=0; j<times.length; j++) 
 total += times[j];
 
 System.out.println("Mean = " + total/1000.0);

But the mean is wildly thrown off -- for some reason, the first iteration of the function (on many runs) takes upwards of a million nanoseconds:

Pic of initial terminal output

Every iteration after the first dozen or so takes either 395 nanos or 0 -- so there could be a problem there too... not sure what's going on!

Also -- the code of the recursive function I'm timing:

static int triangle(int n) 
 if (n == 1) 
 return n;
 else 
 return n + triangle(n -1);
 

Initially I had the line n = Math.abs(n) on the first line of the function, but then I removed it because... meh. I'm the only one using this.

I tried a number of different suggestions brought up in this SO post, but they each have their own problems... which I can go into if you need.

Anyway, thank you in advance for your help and expertise!