brute force standard array roller for https://rpg.stackexchange.com/q/204051

CalculateStandardArray.java

import java.util.Arrays;
import java.util.Random;

public class CalculateStandardArray {

    private static final Random RANDOM = new Random();

    public static void main(String[] args) {
        int numStats = 12;
        int numTrials = 10_000_000;

        int[] totals = new int[numStats];
        int[] rolls = new int[numStats];
        double[] means = new double[numStats];

        while (true) {
            long startNanos = System.nanoTime();

            Arrays.fill(totals, 0);

            for (int j = 0; j < numTrials; j++) {
                for (int i = 0; i < numStats; i++) rolls[i] = roll3DT(); // change to roll3D6 or roll4DTDropLowest, etc
                Arrays.sort(rolls);
                for (int i = 0; i < numStats; i++) totals[i] += rolls[i];
            }

            for (int i = 0; i < numStats; i++) means[i] = (double) totals[i] / numTrials;

            long endNanos = System.nanoTime();

            double elapsedSec = (endNanos - startNanos) / 1e9;

            System.out.println(Arrays.toString(means) + " " + elapsedSec);
        }
    }

    private static int roll3DT() {
        return rollDT() + rollDT() + rollDT();
    }

    private static int roll4DTDropLowest() {
        return dropLowest(rollDT(), rollDT(), rollDT(), rollDT());
    }

    private static int roll3D6() {
        return rollD6() + rollD6() + rollD6();
    }

    private static int roll4D6DropLowest() {
        return dropLowest(rollD6(), rollD6(), rollD6(), rollD6());
    }

    private static int dropLowest(int a, int b, int c, int d) {
        int lowest = Math.min(Math.min(a, b), Math.min(c, d));
        return a + b + c + d - lowest;
    }

    private static final int[] DT_FACES = new int[]{2, 3, 3, 4, 5, 6};

    private static int rollDT() {
        return DT_FACES[RANDOM.nextInt(6)];
    }

    private static int rollD6() {
        return RANDOM.nextInt(6) + 1;
    }

}