Optimal route search based on user preferences
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摘要: 本文研究基于用户偏好的最优路径搜索,在预算约束下寻找一条满足用户偏好即关键字和权重偏好的最优路径.此研究问题是NP-hard.为了高效地解决这类查询问题,本文提出新的索引建立方法,在查询阶段利用索引结构过滤出候选节点集.另外,提出基于A*的路径搜索算法来做路径查询,并利用几个有效的剪枝策略加快算法的执行速度.在两个真实的签到数据集上的实验结果证明了本文提出方法的有效性.当预算时间设置为4~7 h时,与已有最好的PACER算法相比,本文的路径搜索算法消耗的查询时间更短.Abstract: This paper studies the methodology for optimal route search based on user preferences, such as keyword and weight preferences, under a constraint. The research problem is NP-hard. To solve the query efficiently, we propose two new index building methods and select candidate nodes for retrieving the established indices. This paper subsequently proposes an A* based route search algorithm to identify the optimal route and use several effective pruning strategies to speed up execution. Experimental results on two real-world check-in datasets demonstrates the effectiveness of the proposed method. When the budget ranges from 4 hours to 7 hours, our algorithm performs better than the state-of-the-art PACER algorithm.
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Key words:
- route search /
- users' preferences /
- A* algorithm
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表 1 符号及其含义
Tab. 1 Nomenclature
符号 含义 $s(v_i)$ 停留兴趣点$v_i$产生的代价 $SC_{k_q}(v_i)$ 关键字$k_q$在兴趣点$v_i$处的评分 $T(v_i, v_j)$ $(v_i$, $v_j)$边代价 $T_{sm} (v_i, v_j)$ $(v_i$, $v_j)$边最小代价 $cost(R)$ 路径$R$的代价 $Gain(R)$ 路径$R$的收益 $Q=(v_s, v_t, K, \Upsilon, \Delta)$ $v_s$为起点, $v_t$为终点, $K$为查询关键字集, $\Upsilon$为关键字权重集, $\Delta$为预算约束 $V_Q$ 查询$Q$的候选节点集 $R_i^k$ 从$v_s$到$v_i$的第$k$条路径 $L_i^k$ 从$v_s$到$v_i$的第$k$条路径的标签 算法1 基于A*的路径搜索算法 输入:查询$Q =(v_s, v_t, K, \Upsilon, \Delta)$, 图$G=(V_Q, E)$, 最小代价矩阵索引$T_{sm}$, 停留时间列表$s$ 输出:最优路径R 1: 初始化一个最大优先队列Q; 2: $R=\varnothing$, $Gain_{\max}= -\infty$, $BS_{\min}= +\infty$; 3: 创建路径标签$L_s^0=\langle(v_s), 0, 0, 0\rangle$; 4: Q.enqueue $(L_s^0)$; 5: $\textbf{While}$ Q不为空 do 6: { 7: $L_i^k=$Q.dequeue; 8: If $L_i^k.f^i (R_{s \to t})\leqslant Gain_{\max}$ then 9: Break; 10: 从路径标签$L_i^k$中取出路径$R_i^k$; 11: 新的候选节点集CandiSet=$V_Q\setminus V_{R_i^k}$; 12: For $v_j$ in CandiSet do 13: { 14: 创建一条路径$R_j^l=R_i^k\cup\{v_j\}$; 15: $cost(R_j^l) = L_i^k.cost(R_i^k) +T_{sm} (v_i, v_j) +s(v_j)$; 16: $finalCost = cost(R_j^l)+T_{sm}(v_j, v_t)$; 17: If $finalCost>{\it\Delta} $ then 18: Continue; 19: 计算路径收益$Gain(R_j^l)$; 20: If $Gain(R_j^l)>Gain_{\max}$ then 21: { 22: $R = R_j^l\cup\{v_t\}$; 23: $Gain_{\max}= Gain(R_j^l)$; 24: $BS_{\min}=finalCost$; 25: } 26: If$Gain(R_j^l)==Gain_{\max}$ $and$ $finalCost < BS_{\min}$ then 27: { 28: $R =R_j^l\cup\{v_t\}$; 29: $BS_{\min}= finalCost$; 30: } 31: 估计收益上界$f^j(R_{s\to t})$; 32: If $f^j (R_{s\to t})\geqslant Gain_{\max}$ then 33: { 34: 创建路径标签$L_l^j = \langle R_l^j, cost(R_l^j), Gain(R_l^j), f^j (R_{s\to t}))\rangle; $ 35: Q.enqueue($L_l^j)$; 36: } 37: } 38: } 39: return $R$; 表 2 数据集的描述性统计信息
Tab. 2 Descriptive statistics of datasets
数据集 兴趣点个数 边数 平均路程时间 关键字个数 SG 1 625 24 969 16.24 min 202 AS 2 609 34 340 11.12 min 252 -
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