Master Thesis - UBC.pptx
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Graph partitioning is a crucial problem for processing and analyzing large graphs. The two main classes of graph partitioners are in-memory partitioners and streaming partitioners. In-memory partitioners require that the entire graph be read into memory before being partitioned into some number, $k$, of partitions. Conversely, a streaming partitioner reads the graph one edge at a time and immediately places the source and destination vertices in a partition, unless they have already been placed. While in-memory partitioners produce higher-quality partitions, they require a large amount of memory and are slow, which makes them less practical for larger graphs. Streaming partitioners can partition large graphs quickly. However, since they lack more information about the overall graph, their placement decisions are not as good as in-memory partitioners, leading to lower-quality partitions. We implemented a two-phase partitioning algorithm (\texttt{2GP}) that combines the best of both worlds. \texttt{2GP} has two phases: first, it buffers a specific amount of an input graph and partitions it using an in-memory partitioner. Then, it partitions the remaining graph using a streaming partitioner. \texttt{2GP} achieves better partition quality than a state-of-the-art streaming partitioner with significantly better performance. We then show that re-ordering the input graph can improve partition quality still further, without taking significantly more time.
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- 1. 2GP: A Two-Phase Graph Partitioner Hadi Sinaee Supervisor: Margo Seltzer
- 2. 2GP: A Two-Phase Graph Partitioner Hadi Sinaee Supervisor: Margo Seltzer
- 3. 2GP: A Two-Phase Graph Partitioner Hadi Sinaee Supervisor: Margo Seltzer
- 4. 2GP: A Two-Phase Graph Partitioner Hadi Sinaee Supervisor: Margo Seltzer
- 5. 2GP: A Two-Phase Graph Partitioner Hadi Sinaee Supervisor: Margo Seltzer
- 6. We Use Graphs To Model Relationships 6
- 8. Common Algorithms We Use On Graphs! 8
- 9. 9 PageRan k *all images are taken from Wikipedia Community Detection BFS & DFS We Frequently Need to Traverse Neighbors!
- 10. What Is the Problem? 10
- 11. What is the problem? 11 - They may not fit into a single machine! - Algorithms get slow!
- 12. 12 Break Them Apart and Process in Parallel!
- 13. 2GP: A Two-Phase Graph Partitioner Hadi Sinaee Supervisor: Margo Seltzer
- 14. Graph Sub graph Sub graph . . . Sub graph Part-2 Part-3 Part-K Sub graph Part-1 ● A Graph ● K Units of Computation 14 . . .
- 15. How to Measure the Partitioning Quality? 15
- 16. 16 Balanced Partitions # Edge-Cuts Communication Volume (CV) #Nodes Per Partition, or #Edges Per Partition Edge-Cuts: 2 Edge-Cuts: 3 1 1 0 0 2 CV: 1 + 1 + 2 = 4 CV: 1 + 1 + 1 + 1 +2 = 6 1 1 1 1 2
- 17. 17 There are different partitioning algorithms! In-Memory v.s. Streaming
- 18. 18 In-Memory Streaming DRA M DRA M Input Graph 1 1: Load 2 2: Partition Input Graph 2 2: Partition 1 1: Load DRA M Low quality partitions! Fast partitioning! Low memory demand! High quality partitions! Slow partitioning! High memory demand!
- 19. 19 High Low Slow Fast In-Memory Partitioners Streaming Partitioners Partition Quality (# edge-cuts or communication volume) Time
- 20. Can we combine the best of both worlds? a partitioner with the partition quality of in-memory and the speed of streaming 20
- 21. Streaming partitioners are fast but lack neighborhood information of nodes! 21
- 22. 22 As Much as We Can! In-Memory Partitioner Streaming Partitioner Input Graph
- 23. 2GP: A Two-Phase Graph Partitioner Hadi Sinaee Supervisor: Margo Seltzer
- 26. METIS 26 In-Memory - Smaller graphs are easier to partition - It has three phases: - Coarsening - Partitioning - Un-coarsening METIS produces high quality partitions! But it gets really slow and cannot handle large graphs!
- 28. FENNEL 28 Streaming - FENNEL is a vertex-based partitioner. - Input format is an adjacency list and we place only the source vertex for each list. - Calculate a score for each partition - Scores are based on the number of available neighbors in each partition
- 30. Let’s put 2GP Into Test! 30
- 31. Let’s pass the most information to streaming partitioner! 31 Let’s go with higher degrees!
- 32. Communication Volume (CV) High-Degree Ordering 32 - See the effect of CV for different number of partitions! - We choose Twitter graph with 41M nodes and 1.2B edges
- 33. Why Did It FAIL? 33 HDO tends to create highly connected graphs! Partitioning highly connected graphs are harder!
- 34. Communication Volume (CV) Low-Degree Ordering (LDO) 34 Lesson 1: LDO ordering is better than HDO ordering when using 2GP!
- 35. Observation! 35 There many nodes with less than 50% of their neighbours partitioned!
- 36. 36 Delay partitioning of any high-degree node that less than 50% of its neighbors are partitioned! (Average node degree in the graph) * FIXED_FACTOR FENNEL - DelayPart Streamin g
- 37. Communication Volume (CV) Lowest-Degree Ordering with Delayed Partitioning 37 Lesson 2: Delaying high-degree nodes for partitioning later makes CV better!
- 39. Experiments 39 Environment - 28 CPUs; 2 Threads per core; 14 Cores - Intel(R) Xeon(R) W-2275 CPU @ 3.30GHz - 130GB DRAM Datasets - Dblp-cite (12K, 49K) - Dimacs9-USA (23M, 28M) - Twitter (41M, 1.2B) Baselines - METIS (in-memory) - FENNEL (streaming) Metrics Measuring the following across different #partitions: - Communication Volume (CV) - Partitioning Time
- 44. 44 Twitter (41M, 1.2B) 2GP produces better partitions than Fennel even with a small % of input graph given to it!
- 48. 48 Twitter (41M, 1.2B) 2GP is faster than Fennel for small % of input graph! The overhead comes from the repartition part which can be mitigated by adjusting how we choose high-degree nodes.
- 49. Performance 49
- 50. - Won Quality - Won Time - Won Quality - Won Time
- 52. 52 Dimacs9-USA (23M, 28M) Twitter (41M, 1.2B) 1. There is a trade-off between CV and Time! 2. Skewed degree dist are harder to optimize for!
- 53. Conclusion 53 - We can leverage the best-of-both worlds of in-memory and streaming partitioners. - 2GP can be used as the alternative to FENNEL when partitioning large graphs - Achieving up to 70% improvement for some datasets. - Delayed re-partitioning policy helps to produce better communication volume. - Lowest-degree ordering helps to partition higher degree nodes better when using a streaming partitioner. Collaboration
Editor's Notes
- OK, Thanks for coming to today’s talk! I want to present Applic … . It was published last yeat at SIGMOD. I find it interesting bec I sort of had a similar idea which these guys implemented! Well, for this talk, first i’ll start with the graph partitioning itself I briefly talk about How people usually do partitioning? And how we decide which partitioning strategy is a good one? After that, I’ll add a missing part to this scenario which is the application: How having a knowledge about the application could change partitioning?
- OK, Thanks for coming to today’s talk! I want to present Applic … . It was published last yeat at SIGMOD. I find it interesting bec I sort of had a similar idea which these guys implemented! Well, for this talk, first i’ll start with the graph partitioning itself I briefly talk about How people usually do partitioning? And how we decide which partitioning strategy is a good one? After that, I’ll add a missing part to this scenario which is the application: How having a knowledge about the application could change partitioning?
- OK, Thanks for coming to today’s talk! I want to present Applic … . It was published last yeat at SIGMOD. I find it interesting bec I sort of had a similar idea which these guys implemented! Well, for this talk, first i’ll start with the graph partitioning itself I briefly talk about How people usually do partitioning? And how we decide which partitioning strategy is a good one? After that, I’ll add a missing part to this scenario which is the application: How having a knowledge about the application could change partitioning?
- OK, Thanks for coming to today’s talk! I want to present Applic … . It was published last yeat at SIGMOD. I find it interesting bec I sort of had a similar idea which these guys implemented! Well, for this talk, first i’ll start with the graph partitioning itself I briefly talk about How people usually do partitioning? And how we decide which partitioning strategy is a good one? After that, I’ll add a missing part to this scenario which is the application: How having a knowledge about the application could change partitioning?
- OK, Thanks for coming to today’s talk! I want to present Applic … . It was published last yeat at SIGMOD. I find it interesting bec I sort of had a similar idea which these guys implemented! Well, for this talk, first i’ll start with the graph partitioning itself I briefly talk about How people usually do partitioning? And how we decide which partitioning strategy is a good one? After that, I’ll add a missing part to this scenario which is the application: How having a knowledge about the application could change partitioning?
- OK, Thanks for coming to today’s talk! I want to present Applic … . It was published last yeat at SIGMOD. I find it interesting bec I sort of had a similar idea which these guys implemented! Well, for this talk, first i’ll start with the graph partitioning itself I briefly talk about How people usually do partitioning? And how we decide which partitioning strategy is a good one? After that, I’ll add a missing part to this scenario which is the application: How having a knowledge about the application could change partitioning?
- Usually we have a graph and an environment which has k units of computation. The goal here is to utilize all these resources. Why? Besides the fact we’ve paid for that, we want to increase the parallelism! So, we take a graph and create a set of sub-graphs and call them partition. Next, we run our algorithm on each them. For example, we could assign each of theses partitions to a cpu to run our algorithm. Or, we could assign it to different nodes in a cluster network! Now! The questions here are that how do we do the partitionin? And which partitioning is considered a good one!
- OK, Thanks for coming to today’s talk! I want to present Applic … . It was published last yeat at SIGMOD. I find it interesting bec I sort of had a similar idea which these guys implemented! Well, for this talk, first i’ll start with the graph partitioning itself I briefly talk about How people usually do partitioning? And how we decide which partitioning strategy is a good one? After that, I’ll add a missing part to this scenario which is the application: How having a knowledge about the application could change partitioning?