Method heterogenousUnion

src/main/java/net/agkn/hll/HLL.java:653–809

(final HLL other)

     *        cannot be <code>null</code>.
     */
    /*package, for testing*/ void heterogenousUnion(final HLL other) {
        /*
         * The logic here is divided into two sections: unions with an EMPTY
         * HLL, and unions between EXPLICIT/SPARSE/FULL
         * HLL.
         *
         * Between those two sections, all possible heterogeneous unions are
         * covered. Should another type be added to HLLType whose unions
         * are not easily reduced (say, as EMPTY's are below) this may be more
         * easily implemented as Strategies. However, that is unnecessary as it
         * stands.
         */

        // ....................................................................
        // Union with an EMPTY
        if(HLLType.EMPTY.equals(type)) {
            // NOTE:  The union of empty with non-empty HLL is just a
            //        clone of the non-empty.

            switch(other.getType()) {
                case EXPLICIT: {
                    // src:  EXPLICIT
                    // dest: EMPTY

                    if(other.explicitStorage.size() <= explicitThreshold) {
                        type = HLLType.EXPLICIT;
                        explicitStorage = other.explicitStorage.clone();
                    } else {
                        if(!sparseOff) {
                            initializeStorage(HLLType.SPARSE);
                        } else {
                            initializeStorage(HLLType.FULL);
                        }
                        for(final long value : other.explicitStorage) {
                            addRaw(value);
                        }
                    }
                    return;
                }
                case SPARSE: {
                    // src:  SPARSE
                    // dest: EMPTY

                    if(!sparseOff) {
                        type = HLLType.SPARSE;
                        sparseProbabilisticStorage = other.sparseProbabilisticStorage.clone();
                    } else {
                        initializeStorage(HLLType.FULL);
                        for(final int registerIndex : other.sparseProbabilisticStorage.keySet()) {
                            final byte registerValue = other.sparseProbabilisticStorage.get(registerIndex);
                            probabilisticStorage.setMaxRegister(registerIndex, registerValue);
                        }
                    }
                    return;
                }
                default/*case FULL*/: {
                    // src:  FULL
                    // dest: EMPTY