code: Map<Integer, List<Integer>> initTreeMap() {
          Map<Integer, List<Integer>> treeMap = new LinkedHashMap<>(numWorkers);
          for(int r = 0; r < numWorkers; r++) {
              treeMap.put(r, getNeighbours(r));
          }
          return treeMap;
      }
docs: Generates a mapping node -> neighbours(node)