1. Patterns And A Generative Model Jan 24, 2014 Authors: Jianwei Niu, Wanjiun Liao, Jing Peng, Chao Tong Presenter: Guoming Wang Published: Performance Computing and Communications Conference (IPCCC), 2012 IEEE 31st International

2. Nanyang Technological University | Outline ▪ Introduction ▪ Definitions And Properties ▪ Observations ▪ Model

3. Nanyang Technological University | Temporal evolution of social networks ▪ How do social network evolve through network? ▪ How do the different components of an entire network form and die? ▪ Is the second largest component in a network really very small in size? Temporal evolution of social networks has attracted considerable interest among researchers

4. Nanyang Technological University | 3 Method Empirical observations Analyze the mergings Propose model ? ! Problem Future work Two types of mergings: 1. mergings between the disconnected components themselves 2. Mergings between the disconnected components and the giant component Datasets studied

5. Nanyang Technological University | 4 Definitions and interested Properties G = (V, E) Graph G consists of a set of nodes V and a set of edges E. GCC Final size of the DCs The typical directed networks can be stated By a “bow-tie” structure, and usually have a giant connected component(GCC) which involves a significantly large fraction of nodes The number of nodes in that DC when it dies. It reveals how large DCs can grow before dying out 1 4 DC Longevity of DCs The disconnected components(DC) of a network are defined as the small components that are not connected to any other components in the network The length of the period from the birth of a DC to its death. It reflects how long the DCs can live before they merge with other DCs 2 3 What properties or patterns can we obtain from the temporal evolution of DCs ?

6. Nanyang Technological University | Observation1 Longevity distribution of DCs in each dataset All plots demonstrate a decaying trend, and after the vertical line x = k, the curves begin to oscillate apparently. The units of the longevity values are in snapshots. The longevity of each DC counts the number of snapshots that such a DC can live in the observation period of each dataset.

7. Nanyang Technological University | Observation2 Final size distribution of DCs in each dataset. The fitted lines and the slopes are shown. The plots demonstrate power laws

8. Nanyang Technological University | Observations Observation1 The curve of the overall DC longevity distribution shows a decaying trend, with oscillations at the tail, indicating that the short-lived DCs account for a large fraction of all the DCs, and the longevity of long-lived DCs do not follow a simple fixed pattern. Observation2(Final Size Power Law(FSPL)) Let sc denote the final size of a disconnected component, and let nc denote the number of disconnected components whose final size are sc. Then nc and sc follow a power law with exponent B

9. Nanyang Technological University | Longevity distribution of DCs that are absorbed by GCC The trend of the curves revealing the similarity between these distributions and the overall longevity distribution shown previously. Which can be regarded as a hint that the majority of DCs are absorbed by the GCC.

10. Nanyang Technological University | Final size distribution of DCs that are absorted by GCC The fitted lines and the slopes demonstrate again the FSPL and similarity between these distributions and the overall final size distribution

11. Nanyang Technological University | Longevity distribution of DCs that merge with other DCs The curves show a decaying trend, where short-lived DCs are common. There are still small spikes in the decaying part of the curves, and after that, the curves enter a relatively stable state.

12. Nanyang Technological University | Final size distribution of DCs that merge with other DCs

13. Nanyang Technological University | Different timestamp

14. Nanyang Technological University | Mergings of Disconnected Components A DC can either be absorbed by the GCC, or merge with other DCs; The target is to know if there is an obvious difference in number between these two types of mergings Number of DCs is much less compared with the mergings involving the GCC. Long-lived DCs are seldom involved in the DC mergings The count of DCs decreases as the longevity value increases.

15. Nanyang Technological University | Observation3 The mergings among DCs are all small in size, and specially most of the mergings happen between two DCs.

16. Nanyang Technological University | Proposed Model ▪ The decaying trend in DC longevity distribution ▪ The FSPL in the final-size distribution of DCs ▪ The small merging sizes

17. Nanyang Technological University | Surfer Model – generative steps 1. v chooses a host node u uniformly at random from all the existing nodes in the network, and forms a link to u 2. Generate a random number count which is geometrically distributed with expectation pfrnd/(1- pfrnd).Node v randomly chooses count edges of u expect the edge as it can if there are not enough edges. 3. Let x1, x2…xk denote the nodes on the other ends of these chosen edges in step(2). Node v forms links to x1, x2…xk, and then goes to step(2), recursively visiting all these nodes

18. Nanyang Technological University | Surfer Model – Generative steps depiction

19. Nanyang Technological University | Pseudo code

20. Nanyang Technological University | Pseudo code

21. Nanyang Technological University | 20 Conclusion and Future work Empirical observations and analyse longevity and final sizeof DC Detecting anomalies and forcasting the future states…? Surfer model Longevity: decaying trend Final-size: power law

22. Nanyang Technological University | 21 Thank you – Enjoy the rest of your night