Apache Spark GraphX and Graph Processing 3

Question 1

What does the Triangle Count algorithm in GraphX compute for each vertex?

Accepted Answer

The number of triangles that the vertex participates in

Answer

The number of vertices with exactly three neighbors

Answer

The ratio of triangles to total possible triangles (clustering coefficient)

Answer

The depth of the graph's triangular hierarchy

Question 2

What does `joinVertices` allow you to do in GraphX?

Accepted Answer

Update vertex attributes by joining graph vertices with values from an external RDD

Answer

Merge two separate graphs by matching on common vertex IDs

Answer

Join vertex data with edge data to create enriched triplets

Answer

Combine two VertexRDDs using a union operation

Question 3

What is the Label Propagation Algorithm (LPA) used for in GraphX?

Accepted Answer

Detecting communities or clusters in a graph

Answer

Assigning sequential labels to all vertices for indexing

Answer

Propagating error flags through a distributed pipeline

Answer

Annotating edges with semantic relationship types

Question 4

How do you access the underlying distributed data of a GraphX graph as standard RDDs?

Accepted Answer

graph.vertices and graph.edges

Answer

graph.toRDD()

Answer

graph.toDataFrame()

Answer

graph.repartition()

Question 5

What is the key advantage of the `EdgePartition2D` strategy in GraphX over `EdgePartition1D`?

Accepted Answer

It reduces vertex replication by hashing both source and destination IDs when assigning edges to partitions

Answer

It stores edges in a 2D matrix layout for faster adjacency lookups

Answer

It partitions edges into exactly two dimensions of storage blocks

Answer

It reserves separate partitions for inbound and outbound edges

Question 6

In Pregel's execution model as implemented in GraphX, what happens to a vertex that receives no messages in a superstep?

Accepted Answer

The vertex does not execute its vertex program and remains unchanged

Answer

The vertex is removed from the graph

Answer

The vertex sends a null message to all of its neighbors

Answer

The vertex program executes using a default empty message value

Question 7

What is the primary use-case limitation of GraphX compared to dedicated graph databases such as Neo4j?

Accepted Answer

GraphX is not designed for low-latency, transactional (OLTP-style) single-vertex lookups

Answer

GraphX cannot represent directed graphs

Answer

GraphX does not support iterative graph algorithms

Answer

GraphX requires the entire graph to fit in memory on a single machine