Computer Laboratory

MPhil, Part III, and Part II Project Suggestions (2014-2015)

Project Suggestions











Please contact Eiko Yoneki (email: if you are interested in any project below.

1. Clustering Entities across Multiple Documents in Massive Scale

Originator/Supervisor: Eiko Yoneki

Keywords: Clustering, Graph Partitioning, Random Walk, Distributed Algorithms

Many large-scale distributed problems, including the optimal storage of large sets of graph structured data over several hosts, are crucial for today’s Cloud infrastructure. However, in very large-scale distributed scenarios, state-of-the-art algorithms are not directly applicable, because frequent global operations over the entire graph are difficult. In [1], balanced graph partitioning is achieved by a fully distributed algorithm, called Ja-be-Ja, which uses local search and simulated annealing techniques for graph partitioning. The algorithm is massively parallel: each node is processed independently, and only the direct neighbours of the nodes and a small subset of random nodes in the graph need to be known locally. Strict synchronisation is not required. These features allow Ja-be-Ja to be easily adapted to any distributed graph processing system. This will involve the understanding of Ja-be-Ja as a starting point, and investigate further performance improvements. A case study: a graph-based approach to coreference resolution, where a graph representation of documents and their context is used, and applying a community detection algorithm based on [1] can speed up the task of coreference resolution by a very large degree.


[1] Fatemeh Rahimian, Amir H. Payberah, Sarunas Girdzijauskas, Mark Jelasity and Seif Haridi: JabeJa: A Distributed Algorithm for Balanced Graph Partitioning, IEEE International Conference on Self-Adaptive and Self-Organizing Systems (SASO), 2013.

[2] Fatemeh Rahimian, Amir H. Payberah, Sarunas Girdzijauskas, and Seif Haridi: Distributed Vertex-Cut Partitioning, DAIS, 2014.

[3] Fatemeh Rahimian: Gossip-Based Algorithms for Information Dissemination and Graph Clustering, PhD Thesis, 2014.


2. Sampling and Approximation for Triangle Counting in Massive Graph Computation

Originator/Supervisor: Eiko Yoneki

Keywords: Sampling, Approximation, Triangle Counting, Cluster Coefficient, Big Data

Graphs are becoming important to analyse the data. Two key metrics used to characterise a graph are its triangle count (TC) and its clustering coefficient (CC). Both metrics give an intuition of the community structure. When the data volume gets larger or the data rate becomes higher, we need to sample/approximate for speeding up data processing. We have extended the methods presented in [1] to allow the approximation of the TC and CC of graphs stored in external memory on a single machine. These methods are based on wedge sampling. A wedge is a path of length 2: a pair of edges sharing a vertex. As is often the case for graph computations, the algorithms we use show a lack of locality in memory accesses. Key to our approach is the parallel prefetching of memory accesses which will be needed in the future. This project addresses this parallel prefetching, where you need a smart indexing system, in which the graph is stored in such indexed form (e.g. CSR). The project will fully explore sampling and approximation techniques and investigate the format of the graph data, including reading the data in streaming manner such as described in X-Stream [2]. As an extension, local TC and CC could be explored.


[1] C. Seshadhri, A. Pinar, and T. G. Kolda. Triadic measures on graphs: the power of wedge sampling. CoRR, abs/1202.5230, 2013.

[2] Amitabha Roy, Ivo Mihailovic, Willy Zwaenepoel: X-Stream: Edge-centric Graph Processing using Streaming Partitions. SOSP 2013


3.  Approximate Algorithms Determining Local Clustering Coefficients Anonymously

Originator/Supervisor: Eiko Yoneki (with Amitabha Roy (EPFL))

Keywords: Sampling, Approximation, Privacy, Cluster Coefficient

Anonymous social networks are a new phenomenon in an increasingly privacy conscious world. A natural question to ask in this setting is whether we can continue to apply known principles of network science in such settings where neighbourhood information is concealed both between nodes and to external observers. This project is to work on approximate algorithms that determines clustering coefficient in such settings. Clustering coefficients provide a way to relatively order nodes by importance in a network, determine densely connected neighbourhoods and distinguishing social graphs from web graphs. Algorithms to measure clustering coefficients have hitherto required global knowledge of graph links. This requires individual nodes in the graph to give up the identity of their neighbours. This project investigates an algorithm for estimating the clustering coefficient of a vertex by exchanging only anonymised set summaries of neighbours, from which it is difficult to reverse engineer individual links. The bulk of the work will consist of working on and improving sampling techniques to arrive at accurate local clustering coefficients without exchanging explicit neighbour lists in social networks.

[1] P. Flajolet, ric Fusy, O. Gandouet, and et al. Hyperloglog: The analysis of a near-optimal cardinality estimation algorithm. In Proceedings of the International Conference on Analysis of Algorithms, 2007.

4. Graph Compression

Originator/Supervisor: Eiko Yoneki (with Weixiong Rao)

Keywords: Graph Compression

This project explores graph compression mechanisms as part of a project looking into high performance semi-external memory graph processing (see [1] to get an idea of semi-external memory approaches). The graph compression work will build on an in-house graph representation format that we have developed that allows succinct representation of graphs that show hierarchical structures. The project will explore ways to improve the representation yielding smaller graphs on disk that are less costly to traverse. A key element of the representation scheme is a recursive graph partitioning step that minimises the number of edges between partitions. This is a rich space for exploration of suitable algorithms. We are concerned primarily with experimentally evaluating I/O costs on large graphs and measuring the compression performance. However a student with a theoretical background might consider designing algorithms with provable bounds on compression performance, which would be a big plus. If time allows you could also implement an efficient transformation tool based on the developed graph compression algorithm using parallel processing tools (e.g. map/reduce).


[1] R. Pearce, M. Gokhale and N. Amato: Multithreaded Asynchronous Graph Traversal for In-Memory and Semi-External Memory, ACM/IEEE High Performance Computing, Networking, Storage and Analysis, 2010.


5. Develop Scale-Out SSD based Graph Traversal Platform

Originator/Supervisor: Eiko Yoneki (with Karthik Nilakant)

Keywords: Graph processing, I/O optimisation, Graph structure

This project contributes to our ongoing work on high performance semi-external memory graph processing (see [1]). We have developed an in-house prefetching algorithm for mining large graphs stored on Solid State Drives. A solid state drive provides the ability to service many random reads in parallel, provided that the requesting application is able to deliver requests at a rate that keeps the drive sufficiently busy. Thus pre-fetching multiple pages based on the current request in an “intelligent” manner can greatly improve performance. Our current pre-fetcher implementations are aligned with the graph traversal approach, (that is the “graph iterator” being employed).

Furthermore, the prefetcher implementation could be extended to utilise multiple storage devices in parallel. The aim in this setting would be to out-perform standard storage parallelisation techniques such as hardware or software RAID. The performance of this approach would also depend on the method of dividing graph data between available storage devices. Your task is developing scale-out version of our current work. You could also extend it in distributed graph traversals to study how a large graph (e.g. over 2 billion vertices) could get benefits from scale-out version, even though the current version can handle large graphs as a single node. You could also explore generating a large graph for testing by combining various entities of social network data (e.g. what happens when every "Like", "Comment" and "Photo" on Facebook are treated as vertices inside a graph -- not just "People" and "Pages" - such graphs would be huge).


[1] E. Yoneki and A. Roy: Scale-up Graph Processing: A Storage-centric View.  ACM SIGMOD - GRADES, 2013.

[2] GraphLab:


6. Building Graph Query Function using Functional Programming

Originator/Supervisor: Eiko Yoneki (with Karthik Nilakant)

Keywords: Graph, Functional programming

Demand to store and search of online data with graph structure is emerging. Such data range from online social networks to web links and it requires efficient query processing in a scalable manner. In this project, you will build a graph query function (layer) to achieve efficient graph data processing. The graph query function builds on a lazy graph loaded from multiple sources and performs queries at the same speed or faster than a relational database. The function should be written in Clojure or another functional language to support practical lazy loading from data source to an in-memory graph database. Efficient representations for graph queries should be also investigated. The evaluation includes comparisons with existing Graph Database and the query capability comparing with SQL. You can start the project by our existing work in this area.


[1] Microsoft Research: Trinity project: Distributed graph database,

[2] Neo Technology, Java graph database,


7. RasPi-Net: Building Stream Data Processing Platform over RasPiNET

Originator/Supervisor: Eiko Yoneki

Keywords: Raspberry Pi, Delay Tolerant Networks, Satellite Communication, Stream Processing

We have built a decentralised Raspberry Pi network (RasPiNET [1]), which can be deployed in wild and remote regions as a standalone network. The gateway Raspberry Pi nodes are integrated with satellite communication devices, where the light version of Delay Tolerant Network (DTN) bundle protocol is embedded. RasPiNET could consist of 10-100 nodes. As an example, a remote sensing application could be written either in RasPi or Smart phones that can connect to RasPi. Collected data could be processed within RasPiNET to reduce data size that streams over the satellite communication to the base location. The crowd sourcing application can also run on top of RasPiNET. The goal of this project is to build a stream processing platform in both directions: from data collection from RasPiNET nodes to the data processing nodes possibly via a satellite gateway and from bulk of data delivery to the satellite gateway node to disseminate necessary information to RasPiNET nodes. A good filtering function and RasPiNET in-network data aggregation could be developed.


[1] E. Yoneki: RasPiNET: Decentralised Communication and Sensing Platform with Satellite Connectivity.  ACM CHANTS, 2014.

[2] Delay Tolerant Network Bundle Protocol:

[3] RockBlock Technology:


8. Raspberry-BSP: Cheap and Safe Bulk Synchronous Processing on Wimpy Nodes

Originator/Supervisor: Eiko Yoneki  (with Karthik Nilakant)

Keywords: Graph Processing, Data Parallel, Bulk Synchronous Processing

This project is inspired by FAWN [1] and aims to replicate the benefit of an array of low power processors backed by persistent storage to graph mining. The aim is to build a software stack for Raspberry-PI that allows a set of such devices, each equipped with either an SD card or a USB flash drive to act as a node for Bulk Synchronous Processing of graphs (see Pregel [2] for an example of bulk synchronous processing). All the necessary data structures will reside on Flash with the small 256MB RAM on the Raspberry-PI acting as a scratchpad. The aim will be to show that when processing time, energy consumption and cost are taken together this solution is competitive to running BSP on a cluster of PCs.


[1] D. Andersen, J. Franklin, A. Phanishayee, L. Tan and V. Vasudevan: FAWN: A Fast Array of Wimpy Nodes, Communications of the ACM, July 2011.

[2] G. Malewicz, M. Austern, A. Bik, J. Dehnert, I. Horn, N. Leiser, and G. Czajkowski: Pregel: A System for Large-Scale Graph Processing, SIGMOD, 2010.

9. Building Dynamic Time-Dependent Multicast Tree in Twitter Networks

Originator/Supervisor: Eiko Yoneki (with Valentin Dalibard)

Keywords: Joint Diagonalisation, Multicast Tree, Time-Dependent Spread Mode, Content Distribution Simulation, Twitter

The content diffusion occurs spontaneously in online social networks based on the network topology built by the followers, the content cascades. This project aims at investigating the characteristics of such dynamic and temporal cascading trees, which may appear as multiple different spanning trees even from the same source node depending on the contents or depending on the time. The ultimate goal of the project is building multicast trees based on aggregating such spanning trees to accelerate the cascade process and potentially providing a more efficient content delivery process.

The methodology that extracts such spanning trees can be obtained from our previous work on Joint diagonalisation (JD) [1]. JD is a technique used to estimate an average eigenspace of a set of matrices. JD on matrices of spanning trees of a network extracts multiple modes. Note that there is no single underlying static graph in most of real world networks. The average eigenspace may be used to construct a graph which represents the ‘average spanning tree’ of the network or a representation of the most common propagation paths. Examining the distribution of deviations from the average reveals this distribution is multi-modal; thus indicating several modes in the underlying network. These modes are identified and are found to correspond to particular times.

You can explore this project in two ways: 1) modelling multicast tree from aggregation of spanning tree in more theoretical manner or 2) using OSN data and demonstrate the extracted tree and efficiency of multicast tree for content dissemination in content distribution network simulation. 


[1] D. Fay, J. Kunegis, and E. Yoneki: Centrality and Mode Detection in Dynamic Contact Graphs; a Joint Diagonalisation Approach.  IEEE/ACM ASONAM, 2013

[2] Meeyoung Cha, Hamed Haddadi, Fabrício Benevenuto, P. Krishna Gummadi: Measuring User Influence in Twitter: The Million Follower Fallacy. ICWSM 2010.

[3] Evan T.R. Rosenman: Retweets, but Not Just Retweets: Quantifying and Predicting Influence on Twitter. Thesis, Harvard University.


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