private static Set extractKcore()

in hugegraph-core/src/main/java/org/apache/hugegraph/job/algorithm/comm/KCoreAlgorithm.java [195:263]
59 lines of code
13 McCabe index (conditional complexity)

        private static Set<Id> extractKcore(SimilarsMap similarsMap, int k) {
            assert similarsMap.size() == 1;
            Map.Entry<Id, Set<Similar>> entry = similarsMap.entrySet()
                                                           .iterator().next();
            Id source = entry.getKey();
            Set<KcoreSimilar> similars = new HashSet<>();
            for (Similar similar: entry.getValue()) {
                similars.add(new KcoreSimilar(similar));
            }

            boolean stop;
            do {
                stop = true;
                // Do statistics
                Map<Id, MutableInt> counts = new HashMap<>();
                for (KcoreSimilar similar : similars) {
                    for (Id id : similar.ids()) {
                        MutableInt count = counts.get(id);
                        if (count == null) {
                            count = new MutableInt(0);
                            counts.put(id, count);
                        }
                        count.increment();
                    }
                }
                /*
                 * Iterate similars to:
                 * 1. delete failed similar
                 * 2. delete failed intermediaries in survive similar
                 * 3. update statistics
                 */
                Set<KcoreSimilar> failedSimilars = new HashSet<>();
                for (KcoreSimilar similar : similars) {
                    Set<Id> failedIds = new HashSet<>();
                    for (Id id : similar.ids()) {
                        MutableInt count = counts.get(id);
                        if (count.getValue() < k - 1) {
                            count.decrement();
                            failedIds.add(id);
                            stop = false;
                        }
                    }

                    Set<Id> survivedIds = new HashSet<>(CollectionUtils
                                          .subtract(similar.ids(), failedIds));
                    if (survivedIds.size() < k) {
                        for (Id id : survivedIds) {
                            counts.get(id).decrement();
                        }
                        failedSimilars.add(similar);
                    } else {
                        similar.ids(survivedIds);
                    }
                }
                similars = new HashSet<>(CollectionUtils.subtract(
                                         similars, failedSimilars));
            } while (!stop);

            if (similars.isEmpty()) {
                return ImmutableSet.of();
            }
            Set<Id> kcores = new HashSet<>();
            kcores.add(source);
            for (KcoreSimilar similar : similars) {
                kcores.add(similar.id());
                kcores.addAll(similar.ids());
            }
            return kcores;
        }