Abstract
Nowadays personalized influence maximization has become a new branch of influence maximization in social network. The existed methods mainly focus on independent cascade model and linear threshold model, in those two models, nodes’ influence forecast depends on the Monte-Carlo simulation. In order to simulate the propagation of influence more efficiently, we introduce heat diffusion model to the study of personalized influence maximization in this paper. The diffusion process of heat is adopted to simulate the influence of information among users. Furthermore, we propose a target’s heat greedy algorithm based on the analysis of the laws of the heat propagation. Experimental results on real datasets show that our proposed algorithm is effective.
Introduction
Since 2001, the influence maximization (IM) problem in social network has been widely studied [6,11]. Both the range of influence spread and the efficiency of algorithms have been greatly improved [1,2,7,10,12,14]. However, these methods which treat each network user equally fail to satisfy the demands in reality.
Personalized influence maximization [9] is a branch of influence maximization. Due to the long-term marketing and media experiences, enterprises or media services have accumulated some important users. These users are expected to produce far greater values than that of ordinary users. However owing to budget limits, enterprises or media are unable to spread the influence to all friends of the important users at the initial stage. The purpose of personalized influence maximization is to find a set of initial users (referred as seeds) of size k which can maximally influence a specific user (referred as target node). Currently, the social data analysis company as Klout, PeerIndex is using influence maximization algorithm for Marketing consulting [15]. With the development of personal values in business marketing, seeking effective personalized influence maximization algorithm should be the new requirements of social data researcher. To address the issue, we propose a heat diffusion model based algorithm. The results obtained by conducting the experiments on different datasets validate the effectiveness of the proposed algorithm.
The rest of the paper is organized as follows. Section 2 briefly reviews the related works. Section 3 describes the propagation mechanism of heat diffusion model (HDM). Section 4 gives a greedy algorithm based on investigating the propagation characteristics of HDM. Section 5 presents the experiments and analyses. Section 6 draws a conclusion.
Related works
Since the personalized influence maximization was raised in 2013, various algorithms including Random, LND, local greedy algorithm (LGA) and the optimization methods have been proposed [8,9,15]. LND and Random do not couple with influence propagation models. Their problem solving strategies are simple and cannot guarantee the desired solution. Guo et al. [9] put forward LGA based on independent cascade model. It could forecast the influence from nodes to the target by conducting Monte-Carlo simulation on each edge of network. For the sake of improve efficiency, they proposed an efficient local greedy algorithm (ELGA) which takes the whole network as the Monte-Carlo simulation object, instead of each edge of the network. By doing so, the times of performing Monte-Carlo simulation can be greatly reduced. However, ELGA is still time consuming compared to LND and Random. For example, ELGA takes
In [13], Ma et al. proposed a social network marketing model named heat diffusion model that applies heat diffusion theory from physics to describe the diffusion of influence in social network. HDM is applicable to undirected graph, directed graph, and directed graph containing prior knowledge. In their studies, the influence propagation is not simulated by Monte-Carlo simulations. Furthermore, Doo et al. [4,5] extended the HDM of directed graph to make node’s heat flow to other adjacent nodes with a probability. By using HDM, the range and strength of influence propagation can be obtained with a simulation, and influenced strength on target node can be computed at different time. Based on the HDM, Chen et al. [3] proposed an algorithm called CIM to solve the classic influence maximization. However, the HDM based personalized influence maximization remains unresolved. In this paper, we present target’s heat greedy algorithm to solve the problem.
HDM based influence propagation
It is a natural physical phenomenon that heats flows to the low temperature position from a high temperature position in medium. The influence propagation among users in a social network likes heat propagation in a physical medium. The influence propagation tends to transfer information to the one who have yet been influenced, and highly influenced users are prone to propagate information to marginally influenced ones. Therefore, heat diffusion model is applied to simulate the influence spread in social network.
In existed studies, a social network is treated as a directed graph and denoted by
The heat received by a node
For example, given a network in Fig. 1, supposing that

Topological graph.
At time 0, we obtain:
According to equation (3), different elements in the main diagonal of the matrix H, such as
On the basis of equation (2), the heat of each node is computed and shown in Fig. 2.

Heat diffusion.
Take node
The HDM based personalized influence maximization problem is defined as follows:
Given a target user
The analysis of the issues on personalized influence maximization
On the basis of the definition, we know that the issue to be solved lies in
By analyzing HDM and using the left distributive law of matrix multiplication, the equation (2) is decomposed as follows:
Only the nodes in
Target’s heat greedy algorithm
Based on the law of influence propagation and the definition of

THGA
This algorithm firstly initializes the seed set S (line. 1). To collect the influence reaching the target node
In order to better understand the algorithm, the

The graph after removing the edges that taking
H of this graph is presented as
The influenced strength from
Assuming
Given
In order to assess the performance of THGA, k-step [13], LND and Random are selected as reference algorithms. The k-step is similar to THGA, which also employs the greedy strategy based on HDM. However, they are different: k-step aims to solve the classic influence maximization problems. The reason we select k-step as reference is to explore the influenced strength of target node exerted by classic influence maximization seed set. Also, we compare the time consumed by k-step and THGA. The programming language C++ is used to code THGA described in Section 4. The computer on which the code is executed has an Intel Xeon E5-1620 v2 3.70 GHZ processor and a 16 GB memory.
In order to verify the reliability of the experimental results, three social network datasets with different statistic characteristics are selected as test data. All of test data can be gotten from Stanford Network Analysis Platform (
The test datasets
The test datasets
As shown in Table 2, Dataset 1 is a network for the relationships of file exchange based on a peer to peer distributed transfer protocol, Dataset 2 is a network for the voting relationships of the administrators in Wikipedia, and Dataset 3 is a network for the trust relationships among the users from a general consumer review site Epinions.com.

The influenced strength of target node (Dataset 1,
The parameters in the experiments include the size of seed set k, thermal conductivity a, initial influence
Figures 4–6 show the influenced strength of target node on different algorithms in a short time. As demonstrated in the figures, the seed sets obtained by THGA can always exert more favorable influenced strength of target node than k-step, LND and Random. Judging from the influence results of each target node, the seed set obtained by Random presents small influence on target node. With the increase of k, the increment of target influenced strength turns to be minor. Although the increment of target influenced strength obtained by k-step increases more apparently than LND when k is increased, its target influenced strength remains to be less obvious. The great target influenced strength has been found by using LND is on Dataset 1, and it is only slightly smaller than that of using THGA. However, on Datasets 2 and 3, LND is unsatisfactory and quite inferior to THGA. The reason leading to the good performance of LND in Dataset 1 may attribute to inconsistent statistic characteristics of the datasets. Dataset 1 has a certain structural characteristic which is not in other two data sets. THGA achieves preferable target influenced strength on six different target nodes, and the increment of target influenced strength is shown to be stable with the increase of k. As k increases to a certain degree, the target influenced strength tends to be saturated and the increment decreases obviously. This indicates that under these conditions, even the number of seed nodes increases, it contributes less to the increase of target influenced strength.

The influenced strength of target node (Dataset 2,

The influenced strength of target node (Dataset 3,
Figures 7–9 reveal the comparison of the target influenced strength obtained among different algorithms in a sufficient time. As shown in the figures, the influence of seed set obtained by different algorithms spreads sufficiently with the increase of t, which further raises the target influenced strength. Specifically, Random only marginally increases the target influenced strength, and is most inferior. The average target influenced strength of k-step and LND increase 1.71 and 2.37 respectively. However, THGA always shows a superior performance and presents the biggest increment in influence intensity among the four algorithms. For THGA, the average of target influenced strength increased with extension of t is 12.60.

The influenced strength of target node (Dataset 1,

The influenced strength of target node (Dataset 2,

The influenced strength of target node (Dataset 3,
The running time of different algorithms is given in Table 3. The time complexities of LND and Random are
In this paper, based on the analysis of the problems existed in the study of personalized influence maximization, we introduce HDM to simulate the spread of information influence and thus influenced strength of target node can be directly computed. In this way, the issues that traditional models such as independent cascade model and linear threshold model forecast the node influence by relying on lots of extra processes can be overcome. Furthermore, we propose THGA to solve the HDM based personalized influence maximization problem by analyzing the propagation mechanism. Experimental results indicate that THGA is more efficient and effective.
There still exists some interesting work in the future. Firstly, it is worth further study that how to improve the efficiency of the algorithm on the premise of guaranteeing the influenced strength of a target. Secondly, with the availability of big social network data generated by online shopping, advertising and instant messaging, it is also a challenge to identify the users with satisfactory target influenced strength and wide range of influence propagation.
Running time
