## Large-scale Graph Computing at Google

To continue the graph theme Google has got into the act and released information on Pregel. Pregel does not appear to be a new type of potato chip. Pregel is instead a scalable infrastructure...

...to mine a wide range of graphs. In Pregel, programs are expressed as a sequence of iterations. In each iteration, a vertex can, independently of other vertices, receive messages sent to it in the previous iteration, send messages to other vertices, modify its own and its outgoing edges' states, and mutate the graph's topology.

Currently, Pregel scales to billions of vertices and edges, but this limit will keep expanding. Pregel's applicability is harder to quantify, but so far we haven't come across a type of graph or a practical graph computing problem which is not solvable with Pregel. It computes over large graphs much faster than alternatives, and the application programming interface is easy to use. Implementing PageRank, for example, takes only about 15 lines of code. Developers of dozens of Pregel applications within Google have found that "thinking like a vertex," which is the essence of programming in Pregel, is intuitive.

Pregel does not appear to be publicly available, so it's not clear what the purpose of the announcement could be. Maybe it will be a new gmail extension :-)