Find All the Divisors for a Number

In some of my load testing, I want to run a certain number of transactions. My script takes parameters for a number of threads and the number of loops all the threads should go to. When I have a certain target number I want to get to, and an idea of what number of threads I want, I would like to figure out exactly how many loops I need to run for an exact number of threads.

For example, lets say I want to process 16,000,000 transactions with about 300 threads. I can run the following Java class, and figure out that if I use 320 threads, I need 50,000 loops.

	import java.io.*;
	/** Find all the even divisors of a number. */
	class LargestModulus
	{
	/**
	* Find all the divisors for a number (a.k.a., a dividend). The number must be a positive integer. It may be provided on the command line, or entered interactively when prompted.
	*
	* @param args if a command line parameter is detected, the first argument is used.
	*/
	public static void main(final String[] args)
	{
	int num = 0;
	if (args.length == 0)
	{
	final BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
	System.out.print("Enter an integer: ");
	try
	{
	num = Integer.parseInt(reader.readLine());
	}
	catch (final IOException e)
	{
	e.printStackTrace();
	}
	}
	else
	{
	num = Integer.parseInt(args[0]);
	}
	findEvenDivisors(num);
	}
	/**
	* Brute force method to find the even divisors for a number.
	*
	* @param dividend the number to find divisors for
	*/
	public static void findEvenDivisors(final int dividend)
	{
	if (dividend > 0)
	{
	System.out.println("Even divisors for " + dividend);
	for (int i = dividend / 2; i > 0; i--)
	{
	final int modulus = dividend % i;
	if (modulus == 0)
	{
	System.out.println(i + " x " + dividend / i + " = " + dividend);
	}
	}
	}
	else
	{
	System.out.println("ERROR: Number must be > 0");
	}
	System.out.println("=== End ===");
	}
	}

view raw LargestModulus.java hosted with ❤ by GitHub

Enter an integer: 16000000
Even divisors for 16000000
8000000 x 2 = 16000000
4000000 x 4 = 16000000
3200000 x 5 = 16000000
2000000 x 8 = 16000000
1600000 x 10 = 16000000
1000000 x 16 = 16000000
800000 x 20 = 16000000
640000 x 25 = 16000000
500000 x 32 = 16000000
400000 x 40 = 16000000
320000 x 50 = 16000000
250000 x 64 = 16000000
200000 x 80 = 16000000
160000 x 100 = 16000000
128000 x 125 = 16000000
125000 x 128 = 16000000
100000 x 160 = 16000000
80000 x 200 = 16000000
64000 x 250 = 16000000
62500 x 256 = 16000000
50000 x 320 = 16000000
40000 x 400 = 16000000
32000 x 500 = 16000000
31250 x 512 = 16000000
25600 x 625 = 16000000
25000 x 640 = 16000000
20000 x 800 = 16000000
16000 x 1000 = 16000000
15625 x 1024 = 16000000
12800 x 1250 = 16000000
12500 x 1280 = 16000000
10000 x 1600 = 16000000
8000 x 2000 = 16000000
6400 x 2500 = 16000000
6250 x 2560 = 16000000
5120 x 3125 = 16000000
5000 x 3200 = 16000000
4000 x 4000 = 16000000
3200 x 5000 = 16000000
3125 x 5120 = 16000000
2560 x 6250 = 16000000
2500 x 6400 = 16000000
2000 x 8000 = 16000000
1600 x 10000 = 16000000
1280 x 12500 = 16000000
1250 x 12800 = 16000000
1024 x 15625 = 16000000
1000 x 16000 = 16000000
800 x 20000 = 16000000
640 x 25000 = 16000000
625 x 25600 = 16000000
512 x 31250 = 16000000
500 x 32000 = 16000000
400 x 40000 = 16000000
320 x 50000 = 16000000
256 x 62500 = 16000000
250 x 64000 = 16000000
200 x 80000 = 16000000
160 x 100000 = 16000000
128 x 125000 = 16000000
125 x 128000 = 16000000
100 x 160000 = 16000000
80 x 200000 = 16000000
64 x 250000 = 16000000
50 x 320000 = 16000000
40 x 400000 = 16000000
32 x 500000 = 16000000
25 x 640000 = 16000000
20 x 800000 = 16000000
16 x 1000000 = 16000000
10 x 1600000 = 16000000
8 x 2000000 = 16000000
5 x 3200000 = 16000000
4 x 4000000 = 16000000
2 x 8000000 = 16000000
1 x 16000000 = 16000000
=== End ===

Essentially, this provides all the numbers that evenly divide the provided number. Or, in other words, find multipliers that will result in a desired product.