Overview

The K-Hop All algorithm identifies the neighborhood of each node within a graph. This algorithm finds extensive application in various scenarios, including relationship discovery, impact prediction, and friend suggestion.

The K-Hop All algorithm can be considered as the batch execution of the UQL K-Hop Query.

Considerations

Although the K-Hop All algorithm is optimized for high concurrency performance, it is important to note that this algorithm may require significant computational resources when dealing with large graphs (those with tens of millions of nodes or edges), or graphs containing many super nodes. To optimize performance, it is advisable to avoid performing K-Hop All calculation that is excessively deep, considering the specific characteristics and size of the graph being analyzed.

In graph G = (V, E), if |V|/|E|=100, querying the 5-hop neighbors of a node requires a theoretical computational complexity of 10⁵ (equivalent to 10 billion computations), which would take approximately 100ms. Extrapolating from this, completing such a query in a graph with 10 million nodes would require 1 million seconds (equivalent to around 12 days). It's important to consider the computational demands and time requirements when working with graphs of this scale.

Example Graph

To create this graph:

// Runs each row separately in order in an empty graphset
create().node_schema("card").edge_schema("transfer")
create().node_property(@card, "level", int32).node_property(@card, "balance", double)
insert().into(@card).nodes([{_id:"card1", level:1, balance:258.5}, {_id:"card2", level:1, balance:2421.6}, {_id:"card3", level:3, balance:850.71}, {_id:"card4", level:2, balance:4768.8}, {_id:"card5", level:5, balance:1541.55}, {_id:"card6", level:2, balance:3116.7}, {_id:"card7", level:4, balance:3902.8}, {_id:"card8", level:4, balance:27123.8}])
insert().into(@transfer).edges([{_from:"card1", _to:"card2"}, {_from:"card2", _to:"card3"}, {_from:"card2", _to:"card7"}, {_from:"card2", _to:"card7"}, {_from:"card3", _to:"card4"}, {_from:"card4", _to:"card3"}, {_from:"card5", _to:"card2"}, {_from:"card6", _to:"card2"}, {_from:"card7", _to:"card3"}, {_from:"card8", _to:"card3"}])

Creating HDC Graph

To load the entire graph to the HDC server hdc-server-1 as hdc_khop_all:

CALL hdc.graph.create("hdc-server-1", "hdc_khop_all", {
  nodes: {"*": ["*"]},
  edges: {"*": ["*"]},
  direction: "undirected",
  load_id: true,
  update: "static",
  query: "query",
  default: false
})

hdc.graph.create("hdc_khop_all", {
  nodes: {"*": ["*"]},
  edges: {"*": ["*"]},
  direction: "undirected",
  load_id: true,
  update: "static",
  query: "query",
  default: false
}).to("hdc-server-1")

Parameters

Algorithm name: khop_all

File Writeback

This algorithm can generate two files:

CALL algo.khop_all.write("hdc_khop_all", {
  params: {
    return_id_uuid: "id",
    ids: ["card1", "card7"],
    k_start: 2,
    k_end: 3,
    direction: "out",
    node_property: ["@card.level", "@card.balance"],
    aggregate_opt: ["sum", "mean"]
  },
  return_params: {
    file: {
      filename_ids: "neighbors",
      filename: "aggregations"
    }
  }
})

algo(khop_all).params({
  projection: "hdc_khop_all",
    return_id_uuid: "id",
    ids: ["card1", "card7"],
    k_start: 2,
    k_end: 3,
    direction: "out",
    node_property: ["@card.level", "@card.balance"],
    aggregate_opt: ["sum", "mean"]
}).write({
  file: {
    filename_ids: "neighbors",
    filename: "aggregations"
  }
})

Results:

_id,_id
card1,card3
card1,card7
card1,card4
card7,card4

_id,sum,mean,count
card1,9,3174.1,3
card7,2,4768.8,1

DB Writeback

Writes the aggregation results (if has) and the count values to the specified node properties. The property type is double.

CALL algo.khop_all.write("hdc_khop_all", {
  params: {
    k_start: 2,
    k_end: 2,
    node_property: ["@card.level", "@card.level", "@card.balance"],
    aggregate_opt: ["sum", "mean", "mean"]
  },
  return_params: {
    db: {
      property: "khop2"
    }
  }
})

algo(khop_all).params({
  projection: "hdc_khop_all",
  k_start: 2,
  k_end: 2,
  node_property: ["@card.level", "@card.level", "@card.balance"],
  aggregate_opt: ["sum", "mean", "mean"]
}).write({
  db: {
    property: "khop2"
  }
})

The aggregation results are written to new properties sum, mean and mean1; the count values are written to the new property khop2.

Full Return

CALL algo.khop_all("hdc_khop_all", {
  params: {
    return_id_uuid: "id",
    ids: ["card1", "card7"],
    k_start: 2,
    k_end: 3,
    node_property: ["@card.level", "@card.balance"],
    aggregate_opt: ["max", "mean"]
  },
  return_params: {}
}) YIELD r
RETURN r

exec{
  algo(khop_all).params({
    return_id_uuid: "id",
    ids: ["card1", "card7"],
    k_start: 2,
    k_end: 3,
    node_property: ["@card.level", "@card.balance"],
    aggregate_opt: ["max", "mean"]
  }) as r
  return r
} on hdc_khop_all

Result:

Stream Return

CALL algo.khop_all("hdc_khop_all", {
  params: {
    return_id_uuid: "id",
    ids: "card2",
    k_start: 2,
    k_end: 2,
    node_property: ["@card.level", "@card.balance"],
    aggregate_opt: ["max", "max"]
  },
  return_params: {
  	stream: {}
  }
}) YIELD results
RETURN results

exec{
  algo(khop_all).params({
    return_id_uuid: "id",
    ids: "card2",
    k_start: 2,
    k_end: 2,
    node_property: ["@card.level", "@card.balance"],
    aggregate_opt: ["max", "max"] 
  }).stream() as results
  return results
} on hdc_khop_all

Result: