presto-orc/src/main/java/io/prestosql/orc/metadata/statistics/BloomFilter.java/BloomFilter/optimalNumOfHashFunctions
class BloomFilter:    static int optimalNumOfHashFunctions(long n, long m)
    {
        return Math.max(1, (int) Math.round((double) m / n * Math.log(2)));
    }