Counting Triangles

Counting Triangles

From the post:

Recently I’ve heard from or read about people who use Hadoop because their analytic jobs can’t achieve the same level of performance in a database. In one case, a professor I visited said his group uses Hadoop to count triangles “because a database doesn’t perform the necessary joins efficiently.”

Perhaps I’m being dense but I don’t understand why a database doesn’t efficiently support these use-cases. In fact, I have a hard time believing they wouldn’t perform better in a columnar, MPP database like Vertica – where memory and storage are laid out and accessed efficiently, query jobs are automatically tuned by the optimizer, and expression execution is vectorized at run-time. There are additional benefits when several, similar jobs are run or data is updated and the same job is re-run multiple times. Of course, performance isn’t everything; ease-of-use and maintainability are important factors that Vertica excels at as well.

Since the “gauntlet was thrown down”, to steal a line from Good Will Hunting, I decided to take up the challenge of computing the number of triangles in a graph (and include the solutions in GitHub so others can experiment – more on this at the end of the post).

I don’t think you will surprised at the outcome but the exercise is instructive in a number of ways. Primarily don’t assume performance without testing. If all the bellowing leads to more competition and close work on software and algorithms, I think there will be some profit from it.

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