iPregel: Vertex-centric programmability vs memory efficiency and performance, why choose?

Abstract The vertex-centric programming model, designed to improve the programmability in graph processing application writing, has attracted great attention over the years. Multiple shared memory frameworks that have implemented the vertex-centric interface all expose a common tradeoff: programmability against memory efficiency and performance. Our approach consists in preserving vertex-centric programmability, while implementing optimisations missing from FemtoGraph, developing new ones and designing these so they are transparent to a user’s application code, hence not impacting programmability. We therefore implemented our own shared memory vertex-centric framework iPregel, relying on in-memory storage and synchronous execution. In this paper, we evaluate it against FemtoGraph, whose characteristics are identical, but also an asynchronous counterpart GraphChi and the vertex-subset-centric framework Ligra. Our experiments include three of the most popular vertex-centric benchmark applications over 4 real-world publicly accessible graphs, which cover all orders of magnitude between a million to a billion edges. We then measure the execution time and the peak memory usage. Finally, we evaluate the programmability of each framework by comparing it against the original Pregel, Google’s closed-source implementation that started the whole area of vertex-centric programming. Experiments demonstrate that iPregel, like FemtoGraph, does not sacrifice vertex-centric programmability for additional performance and memory efficiency optimisations, which contrasts with GraphChi and Ligra. Sacrificing vertex-centric programmability allowed the latter to benefit from substantial performance and memory efficiency gains. However, experiments demonstrate that iPregel is up to 2300 times faster than FemtoGraph, as well as generating a memory footprint up to 100 times smaller. These results greatly change the situation; Ligra and GraphChi are up to 17,000 and 700 times faster than FemtoGraph but, when comparing against iPregel, this maximum speed-up drops to 10. Furthermore, on PageRank, it is iPregel that proves to be the fastest overall. When it comes to memory efficiency, the same observation applies; Ligra and GraphChi are 100 and 50 times lighter than FemtoGraph, but iPregel nullifies these benefits: it provides the same memory efficiency as Ligra and even proves to be 3 to 6 times lighter than GraphChi on average. In other words, iPregel demonstrates that preserving vertex-centric programmability is not incompatible with a competitive performance and memory efficiency.