@Override
        public boolean equals(Object o) {
            if (o == this) return true;
            if ( ! (o instanceof Distribution other)) return false;
            return (distributionSpec == other.distributionSpec && preCalculatedResults.length == other.preCalculatedResults.length);
        }
The distribution class keeps precalculated arrays for distributions for all legal redundancies. The class is
immutable, such that it can be returned safely out from the group object. (Actually, it's not immutable.)
vdslib/src/main/java/com/yahoo/vdslib/distribution/Group.java