In "BloomFilter" interface, "union" and "intersect" methods returns "false"

[rogerdielrton]

Hi. Congratulations for your Bloom Filter library: is very useful and complete. Come on with my problem: The execution of my test code (see below "MyTest" Java class) fails because "union" and "intersection" methods returns "false": Interface orestes.bloomfilter.BloomFilter:

• Method "union": Return "true" if this bloom filter could successfully be updated through the union with the provided bloom filter.
• Method "intersect": Return "true" if this bloom filter could successfully be updated through the intersection with the provided bloom filter.

Why both returns "false"? What's the meaning of "bloom filter could SUCCESSFULLY be updated"? How to avoid tha "union" and "intersection" works well without returning "false"? Thanks in advance.

public class MyTest {

    public static void main(String[] args) {
        BloomFilter<Long> alpha = new FilterBuilder()
                .expectedElements(50)
                .falsePositiveProbability(0.05)
                .hashFunction(HashMethod.Murmur3)
                .buildBloomFilter();
        fill(1, 50, alpha);     
        BloomFilter<Long> omega = new FilterBuilder()
                .expectedElements(62500)
                .falsePositiveProbability(0.05)
                .hashFunction(HashMethod.Murmur3)
                .buildBloomFilter();
        fill(2, 62500, omega);      
        try {
            System.out.println("Intersection estimated population: " + intersection(alpha, omega).getEstimatedPopulation());
        }
        catch (UnsupportedOperationException uoe) {
            uoe.printStackTrace();
        }
        try {           
            System.out.println("Union estimated population: " + union(alpha, omega).getEstimatedPopulation());
        }
        catch (UnsupportedOperationException uoe) {
            uoe.printStackTrace();
        }
    }

    static BloomFilter<Long> union(BloomFilter<Long> a, BloomFilter<Long> b) {
        BloomFilter<Long> c = a.clone();
        boolean success = c.union(b);
        if (!success) throw new UnsupportedOperationException();
        return c;
    }

    static BloomFilter<Long> intersection(BloomFilter<Long> a, BloomFilter<Long> b) {
        BloomFilter<Long> c = a.clone();
        boolean success = c.intersect(b);
        if (!success) throw new UnsupportedOperationException();
        return c;
    }

    static void fill(int seed, int max, BloomFilter<Long> bf) {
        Random r = new Random(seed); 
        LongStream.rangeClosed(1, max).map(i -> r.nextLong()).filter(i -> i > 0).forEach(i -> bf.add(i));
    }

}

[rogerdielrton]

I found the cause:

FilterBuilder.isCompatibleTo:
    return this.size() == other.size() && this.hashes() == other.hashes() && this.hashMethod() == other.hashMethod();

According to that, because "alpha" and "omega" match in "hashes" and "hash method", but differ on "size", then "intersect" and "union" returns "false".