package it.unibo;

public class VolatilePropagation {

    static volatile int v;
    static int nonVolatile;

    public static void main(final String... args) {
        new Thread(() -> {
            while(true) {
                if (v == Integer.MAX_VALUE) {
                    nonVolatile = 0; // nonVolatile gets reset before v
                    v = 0;
                }
                nonVolatile++; // nonVolatile is always increased before v
                v++;
            }
        }).start();
        new Thread(() -> {
            while (true) {
                final var v1 = v; // nonVolatile is always read along with v
                final var nv = nonVolatile; // Can't be smaller than v
                if (nv < v1) {
                    System.out.println("Unexpected lost update! volatile: " + v1 + " - non volatile: " + nv);
                }
            }
        }).start();
        new Thread(() -> {
            var errors = 0L;
            while (true) {
                final var nv = nonVolatile; // Smaller than v in case of lost update!
                final var v1 = v; // Reversed reading order
                if (nv < v1) {
                    errors++;
                    if (errors % 1_000_000 == 0) {
                        System.out.println("Lost updates in thread 2: " + (errors / 1_000_000) + " millions!");
                    }
                }
            }
        }).start();
    }
}