Apache Spark GraphX and Graph Processing 2

Question 1

What computation model does the Pregel API in GraphX implement?

Accepted Answer

Bulk-synchronous message-passing between vertices

Answer

The Pregel API implements a bulk-synchronous parallel (BSP) message-passing model where vertices send and receive messages in iterative supersteps until convergence.

Question 2

In GraphX's `aggregateMessages`, what is the role of the `sendMsg` function?

Accepted Answer

To define what messages are sent along each edge to neighboring vertices

Answer

The `sendMsg` function is called for each edge triplet and specifies what messages, if any, to send to the source and/or destination vertices for aggregation.

Question 3

What does GraphX's `connectedComponents()` algorithm store as each vertex's attribute in the result graph?

Accepted Answer

The lowest VertexId in its connected component

Answer

connectedComponents() labels each vertex with the lowest VertexId found in its connected component, allowing grouping of all vertices in the same component.

Question 4

What does the `mapVertices` operation in GraphX do?

Accepted Answer

Transforms vertex attributes using a user-defined function without changing graph structure

Answer

mapVertices applies a function to each vertex's attribute and returns a new Graph with the transformed properties while preserving the original topology.

Question 5

What is the purpose of the `subgraph` operation in GraphX?

Accepted Answer

To extract a subset of vertices and edges that satisfy a given predicate

Answer

The `subgraph` operation filters vertices and edges using user-supplied predicates, returning a new graph that contains only the elements satisfying both conditions.

Apache Spark Practice Test

Apache Spark Practice Test

Apache Spark GraphX and Graph Processing 2