Table of Contents – Part I XXIX A Buffered-Mode MPI Implementation for the Cell BE TM Proc

Table of Contents–Part I XXIX A Bu?ered-Mode MPI Implementation for the Cell BE TM Processor (603)

Arun Kumar,Ganapathy Senthilkumar,Murali Krishna,

Naresh Jayam,Pallav K.Baruah,Raghunath Sharma,

Ashok Srinivasan,and Shakti Kapoor

Implementation of the Parallel Superposition in Bulk-Synchronous

Parallel ML (611)

Fr′e d′e ric Gava

Parallelization of Generic Libraries Based on Type Properties (620)

Prabhanjan Kambadur,Douglas Gregor,and Andrew Lumsdaine

Tra?c Routing Through O?-Line LSP Creation (628)

Srecko Krile and Djuro Kuzumilovic

Simulating Trust Overlay in P2P Networks (632)

Yan Zhang,Wei Wang,and Shunying L¨u

Detecting Shrew HTTP Flood Attacks for Flash Crowds (640)

Yi Xie and Shun-Zheng Yu

A New Fault-Tolerant Routing Algorithm for m-ary n-cube

Multi-computers and Its Performance Analysis (648)

Liu Hongmei

CARP:Context-Aware Resource Provisioning for Multimedia over4G Wireless Networks (652)

Navrati Saxena,Abhishek Roy,and Jitae Shin

Improved Fast Handovers for Mobile IPv6over IEEE802.16e Network (660)

Sukyoung Ahn and Youngsong Mun

Advanced Bounded Shortest Multicast Algorithm for Delay Constrained Minimum Cost (668)

Moonseong Kim,Gunu Jho,and Hyunseung Choo

E?cient Deadlock Detection in Parallel Computer Systems with

Wormhole Routing (676)

Soojung Lee

Type-Based Query Expansion for Sentence Retrieval (684)

Keke Cai,Chun Chen,Jiajun Bu,and Guang Qiu

An Extended R-Tree Indexing Method Using Selective Prefetching in

Main Memory (692)

Hong-Koo Kang,Joung-Joon Kim,Dong-Oh Kim,and Ki-Joon Han

Advanced Bounded Shortest Multicast Algorithm for Delay Constrained Minimum Cost Moonseong Kim1,Gunu Jho2,and Hyunseung Choo1,

1School of Information and Communication Engineering

Sungkyunkwan University,Korea

{moonseong,choo}@ece.skku.ac.kr

2Telecommunication Network Business

Samsung Electronics,Korea

jhogunu@https://www.wendangku.net/doc/bb18506166.html,

Abstract.The Bounded Shortest Multicast Algorithm(BSMA)is a

very well-known one of delay-constrained minimum-cost multicast rout-

ing algorithms.Although the algorithm shows excellent performance in

terms of generated tree cost,it su?ers from high time complexity.For

this reason,there is much literature relating to the BSMA.In this paper,

the BSMA is analyzed.The algorithms and shortcomings are corrected,

and an improved scheme is proposed without changing the main idea of

the BSMA.

Keywords:Multicast Routing Algorithm,Delay-Bounded Minimum

Steiner Tree(DBMST)Problem,and Bounded Shortest Multicast Al-

gorithm(BSMA).

1Introduction

Depending on the optimization goals,which include cost,delay,bandwidth, delay-variation,reliability,and so on,the multicast routing problem exists at varying levels of complexity.A Delay-Bounded Minimum Steiner Tree(DBMST) problem deals with the minimum-cost multicast tree,satisfying the delay-bounds from source to destinations.The Bounded Shortest Multicast Algorithm(BSMA) is a routing algorithm which solves the DBMST problem for networks with asym-metric link characteristics[1,2].The BSMA starts by obtaining a minimum delay tree,calculated by using Dijkstra’s shortest path algorithm.It then iteratively improves the cost,by performing,the delay-bounded path switching.The eval-uation performed by the Salama et al.[3]demonstrates that the BSMA is one of the most e?cient algorithms for the DBMST problem,in terms of the gener-ated tree cost.However,the high time complexity presents a major drawback of BSMA,because a k-shortest path algorithm is used iteratively for path switch-ing.There are also several approaches to improve the time complexity of BSMA [4,5].However,among them,none can peer with the BSMA in terms of cost.

Corresponding author.

Y.Shi et al.(Eds.):ICCS2007,Part I,LNCS4487,pp.668–675,2007.

c Springer-Verlag Berlin Heidelberg2007

Advanced BSMA for Delay Constrained Minimum Cost669 The subsequent sections of this paper are organized as follows.In Section2, the BSMA is described.In Section3,then the problems with the BSMA are described and the fact that the BSMA can perform ine?cient patch switching in terms of delays from source to destinations without reducing the tree cost, are presented.A new algorithm is proposed,furthermore,to substitute for the k-shortest path algorithm,considering the properties of the paths used for the path switching.Finally,this paper is concluded in Section4.

2Bounded Shortest Multicast Algorithm

BSMA constructs a DBMST by performing the following steps:

1)Initial step:Construct an initial tree with minimum delays from the source

to all destinations.

2)Improvement step:Iteratively minimize the cost of the tree while always

satisfying the delay bounds.

The initial tree is minimum-delay tree,which is constructed using Dijkstra’s shortest path algorithm.If the initial tree could not satisfy the given delay bounds,some negotiation would be required to relax the delay bounds of DDF (Destination Delay-bound Function).Otherwise,tree construction cannot suc-ceed in satisfying the DDF.

BSMA’s improvement step iteratively transforms the tree topology to decrease its cost monotonically,while satisfying the delay bounds.The transformation performed by BSMA at each iteration of the improvement step consists of a delay-bounded path switching.The path switching replaces a path in tree T j by a new path with smaller cost,resulting in a new tree topology T j+1.It involves the following:

1)Choosing the path to be taken out of T j and obtaining two disjoint subtrees

T1j and T2j

2)Finding a new path to connect T1j and T2j,resulting in the new tree topology

T j+1with smaller cost,while the delay bounds are satis?ed.

A candidate paths in T j for path switching is called a superedge.Removing a superedge from a multicast tree corresponds to removing all of the the tree edges and internal nodes in the superedge.From the de?nition of a superedge[1,2],a destination node or a source node cannot be an internal node of a superedge. This prevents the removal of destination nodes or the source node from the tree as a result of a path switching.

At the beginning of the improvement step,BSMA sets all superedges un-marked and selects the superedge p h with the highest cost among all unmarked superedges.Removing the p h in T j breaks T j into two disjoint subtrees T1j and T2j,where T j=p h∪T1j∪T2j.A delay-bounded minimum-cost path p s between T1j and T2j is used to reconnect T1j and T2j to obtain the new tree topology T j+1, where T j+1=p s∪T1j∪T2j.The cost of p s is not higher than that of p h.

670M.Kim,G.Jho,and H.Choo

The search for the p s starts with the minimum-cost path between the two trees.If the minimum-cost path results in a violation of delay bounds,BSMA uses an incremental k-shortest path algorithm[6]to?nd p s.The k-shortest path problem consists of?nding k th shortest simple path connecting a given source-destination pair in a graph.k-shortest path in BSMA is k-minimum-cost path between two trees and is equivalent to?nding the k-shortest path between the two nodes.Because BSMA uses a k-shortest path algorithm for the path switching,its high time complexity is the major drawback.For this reason,the improvement algorithms are proposed in[4,5].While these reduce the execution time,the performance loss in terms of tree cost is also happened.

3Di?culties in BSMA

3.1Undirected Graph Model for BSMA

It is not mentioned clearly in[1]whether the network model for BSMA is a directed or an undirected graph.Although the?gures in[1]implicate that it is undirected,later version describing the BSMA[2]and other literatures[3,4,5] related to the BSMA simulation state that the network is modeled as a directed graph.But,we argue that it should be an undirected graph.

Fig.1.A case that is able to happen at the step for delay-bounded path switching The following case in Fig.1can be happened during the delay-bounded path switching of BSMA and shows that there could be a problem.Fig.1(a)shows a tree T j before the path switching,of which the highest cost superedge p h is a path from s to r1,as shown.There are two disjoint subtree T1j and T2j in Fig. 1(b)which are calculated by removing the highest cost superedge p h in T j.At this step of the path switching,a delay-bounded shortest path p s is searched. By reconnecting the p s(Fig.1(c)),T j+1is obtained.

As shown in the Fig.1(c),T j+1is a wrong tree,because the source s cannot send anything to destinations d1and d2using T j+1.To convert T j+1in Fig.1(c) to T c in Fig.1(d),that is what the algorithm wants,it must be guaranteed that both path-delays and path-costs of the paths from r1to r2and from r2to r3 are the same as those of paths from r2to r1and from r3to r2,respectively.If the algorithm must guarantee this,it becomes overhead to check all the links in a subtree without source s that is T1j or T2j at every step it performs the

Advanced BSMA for Delay Constrained Minimum Cost 671

path switching.Simultaneously it can severely reduce the possible cases that can make the path switching as many as there are asymmetric links in the tree.Of course,there is no routine to handle this case in BSMA.To avoid this and to contribute to the main idea of the BSMA,the network model should be assumed as the undirected graph.From now on,we use the undirected links,so that (u,v )=(v,u )∈E with the same link-delay and link-cost values.

3.2Meaning of ‘Unmark’the Superedge

The issue of this subsection is about the superedge.There are ?ve superedges in Fig.

1(a),those are p (s,r 1),p (r 1,d 1),p (r 1,r 2),p (r 2,d 2),and p (r 2,d 3).After the path switching,there are di?erent superedges in Fig.1(d),those are p (s,r 3),p (r 3,d 3),p (r 3,r 2),p (r 2,d 2),and p (r 2,d 1).You can see that the superedges change,as the tree changes.The simple paths in Fig.2(a),which redraws the Fig.1(d),are all superedges.The tree in Fig.2(b)is the result by another path switching.And the tree in Fig.2(c)shows the same tree where the simple paths are all superedges.

(a)(b)(c)Fig.2.Changes of superedges as the tree changes

BSMA marks the highest-cost unmarked superedge p h when the superedge is on path switching.If the p h is switched to a delay-bounded minimum-cost path p s ,BSMA unmarks all marked superedges [1,2].If the ?ag value of a superedge is marked,it means there is no path to substitute for the superedge to reduce the current tree T j .When p h is switched to p s ,the tree is changed from T j to T j +1.Of course,BSMA must recalculate the superedges in the new tree T j +1with initializing them as unmarked.

3.3The Delay-Bounded Minimum-Cost Path p s and the Function

to Get the p s Between T 1j

and T 2j According to [1,2],one of two cases must happen when the delay-bounded minimum-cost path p s is obtained:

1.path p s is the same as the path p h ;or

2.path p s is di?erent from the path p h .

If the ?rst case occurs,the p h has been examined without improvement of the tree cost.If the second case occurs,the tree T j +1would be more cost-e?ective

672M.Kim,G.Jho,and H.Choo

tree than T j.But it is possible in the second case to generate the tree T j+1whose cost is the same as that of T j and end-to-end delay between a source and each destination is worse than that of T j.The former cost-e?ective tree T j+1is what the algorithm wants.But the latter tree is not.This is because a path with the same cost as that of p h could be searched as p s.

(a) T

0 : minimum-delay tree

(b) T

1

Fig.3.Ine?ective path switching in terms of end-to-end delay without any improve-ment of tree cost

Fig.3shows the example for that.The values on the simple paths in the Fig.3 are path-delays.The tree T0in Fig.3(a)is a minimum-delay tree generated by using Dijkstra’s algorithm.So,it is sure that the end-to-end delays between the source s and each destination d1,d2,and d3are the minimum values.The tree T1in Fig.3(b)is a tree after the path switching.The p s is a simple path whose path-delay is8and path-cost is the same as that of p h.As a result of the path switching,BSMA generates the ine?ective tree T1in terms of end-to-end delay without any improvement of tree cost.

If BSMA considers only whether the p s is equal to p h or not,this ine?ective path switching is always possible as long as there could be a path whose cost is the same as that of p h while satisfying the delay-bounds.So BSMA must select a path with smaller cost than that of p h,as the p s.(We must note here that the ine?ective path switching does not happen in BSMA based on greedy heuristic, since it performs the path switching when the gain is larger than zero.) Additionally,we need to think about the procedure to determine whether a path is delay-bounded or not.Whenever BSMA?nds the p s,it has to determine whether a path is delay-bounded or not.That is to say,BSMA has to perform one of the followings:

1.construction of a tree from T1j,T2j and a candidate path for p s,for every

candidate until?nding the p s;or

2.pre-calculation of end-to-end delays between a source and each destination

for all cases that the p s would connect T1j with T2j.

The total cost of a tree can be calculated without considering how the nodes in the tree are connected by the links.Because it is the sum of link-costs in the tree,we only need information about which links are in the tree and how

Advanced BSMA for Delay Constrained Minimum Cost

673(b) Candidate path for p s w (c) Pre-calculation

(a) T j 1and T j 2Fig.4.Calculation of end-to-end delays in tree

much their costs are.But end-to-end delay between two tree nodes,such as a source and a destination,is only able to be calculated after considering the tree structure.

Fig.4(a)shows subtrees on BSMA’s path switching and (b)is a candidate path for p s .If the values on the simple paths in Fig.4(a)and (b)are the path-costs,the total cost of a tree T j +1(=T 1j ∪T 2j ∪p s )would be determined when the path-cost w of the candidate is determined (that is 1+2+3+4+w ),without considering how the candidate connects T 1j with T 2j .But if the values indicate the path-delays,it is impossible to determine the end-to-end delays between the source s and each destination d 1,d 2,or d 3without considering the tree structures of T 1j and T 2j .

Obviously there are two ways to determine whether the candidate is delay-bounded or not;one is to construct the tree by connecting T 1j and T 2j with the candidate;the other is to perform a pre-calculation such like Fig.4(c).Of course,both must consider the structures of two subtrees.

3.4Ine?cient Use of k -Shortest Path Algorithm

As the literatures [4,5]mentioned,the k -shortest path algorithm [6]used for ?nding the p s is the major drawback of BSMA.The time complexity of the k -shortest path algorithm is O (kn 3).The k value can be set to a ?xed value to reduce execution time of BSMA.However this also reduces the performance of BSMA in terms of generated tree cost.In this subsection we propose another algorithm to substitute the k -shortest path algorithm.The proposed algorithm ?nds candidate paths for p s within some path-cost range and does not deterorate the performance of BSMA.

According to what we described in subsection 3.3,BSMA do not need the paths whose costs are equal to or larger than that of p h while ?nding p s .And obviously we cannot ?nd any path with smaller cost than that of minimum-cost path calculated by Dijkstra’s algorithm.Consequently,candidate paths for p s are the paths with the cost range that is equal to or larger than that of the minimum-cost path and smaller than that of p h .The following is the pseudo code of the proposed algorithm.

674M.Kim,G.Jho,and H.Choo

Description for internal variables and functions

p[0..(|V|?1)],q[0..(|V|?1)]:an array containing the node sequence for a path index p:the index for p

cost p:the path-cost of p

P:the set of searched paths

Q:queue containing paths on searching

PUSH(Q,p):insert p to Q

POP(Q):take a path out of Q

PROCEDURE PathSearch SameCostRange(T1j,T2j,minCost,maxCost, G)

1.P←?,Q←?;

2.for each node i∈T1j{

3.p[0]←i,index p←0,cost p←0;

4.PUSH(Q,p);

5.}

6.while Q=?{

7.p←POP(Q);

8.for each neighbor node n of p[index p]{

9.if(n is in the array p)then continue;

10.\\Because we are looking for simple paths

11.if(n∈T1j)then continue;

12.\\Because we are looking for paths between T1j and T2j

13.if(cost p+link-cost of(p[index p],n)≥maxCost)then continue;

14.q←p,cost q←cost p,index q←index p;\\Copy p to q

15.q[index q+1]←n;

16.cost q←cost q+link-cost of(q[index q],n);

17.index q←index q+1;

18.if(n∈T2j AND cost q≥minCost)then P←P∪{q};

19.if(n/∈T2j)then PUSH(Q,q);

20.}

21.}

22.return P;

Although a number of candidates for p s are searched,BSMA use only the one satisfying the delay-bounds with smallest cost,that is p s.So BSMA do not need to?nd all the candidates at once.Therefore the arguments minCost and maxCost are not minimum path-cost between T1j and T2j,and path-cost of p h, respectively.The half closed interval[minimum path-cost between T1j and T2j, path-cost of p h)is divide into several intervals to be the minCost and maxCost. BSMA iteratively increases the minCost and maxCost until either?nding p s or recognizing there is no path to substitute p h.

When the network size is large with many links,the memory required to calculate the candidates is also heavy as well as the high time complexity.So,this is quite practical and dose not provide any limitation to BSMA’s performance. The di?erence between minCost and maxCost can be adjusted according to

Advanced BSMA for Delay Constrained Minimum Cost675 characteristic of modeled link-cost.(i.e.If the link-costs is modeled as integer values,minCost and maxCost can be the integer value x and x+1,where x is some starting point of divided interval and1stands for the characteristic.)In the next section,the characteristic is notated as the sys.

4Conclusion

BSMA is very well-known one of delay-constrained minimum-cost multicast rout-ing algorithms.Although,its performance is excellent in terms of generated tree cost,the time complexity is very high.There are many literatures related to BSMA for this reason.We have shown that BSMA has fallacies and ambiguities then,modi?ed it.We start on the describing BSMA[2].Then,we show that the BSMA has fallacies,and that the BSMA can perform ine?cient patch switching in terms of delays from source to destinations without reducing the tree cost. Hence,we propose an algorithm to substitute for the k-shortest path algorithm considering the properties of the paths which are used for the path switching. Acknowledgment

This research was supported by the MIC(Ministry of Information and Com-munication),Korea,under the ITRC(Information Technology Research Center) support program supervised by the IITA(Institute of Information Technology Assessment),IITA-2006-(C1090-0603-0046).

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Constrained Minimal-Cost Multicasting.Proceeding of INFOCOM.IEEE(1995) 377-385

2.Parsa,M.,Zhu,Q.,Garcia-Luna-Aceves,J.J.:An Iterative Algorithm for Delay-

Constrained Minimum-Cost Multicasting.IEEE/ACM Transactions Networking, Vol.6,Issue4.IEEE/ACM(1998)461-474

3.Salama,H.F.,Reeves,D.S.,Viniotis,Y.:Evaluation of Multicast Routing Algo-

rithms for Real-Time Communication on High-Speed Networks.Journal of Selected Areas in Communications,Vol.15,No.3.IEEE(1997)332-345

4.Gang,F.,Kia,M.,Pissinoul,N.:E?cient Implementations of Bounded Shortest

Multicast Algorithm.Proceeding of ICCCN.IEEE(2002)312-317

5.Gang,F.:An E?cient Delay Sensitive Multicast Routing Algorithm.Proceeding

of the International Conference on Communications in Computing.CSREA(2004) 340-348

https://www.wendangku.net/doc/bb18506166.html,wler,E.:Combinatorial Optimization:Networks and Matroids.Holt,Rinehart

and Winston(1976)

高中英语句子翻译200句

句子翻译 1.我是学生.(简单句)______________________________________________________________________________ 2.他在做的与我无关._____________________________________________________________________________ 3.我来了,但他已经走了. (复合句)___________________________________________________________________ 4.我不知道他已经走了,但是她知道. (并列复合句)_____________________________________________________ 5.你能回答我的问题吗___________________________________________________________________________ 6.我在写信.______________________________________________________________________________________ 7.请开门.________________________________________________________________________________________ 8.他是一个多聪明的男孩啊!________________________________________________________________________ 9.我非常喜欢这本书.______________________________________________________________________________ 10.他昨天去哪儿了_______________________________________________________________________________ 第二组：词类 11.你应该用正确的方法做这件事.____________________________________________________________________ 12.最终, 他受到了惩罚.____________________________________________________________________________ 13.他在湖里游泳. He is swimming in the lake. 14.至今,我已经读了100部小说. So far, I have read 100 novels. 15.我不喜欢这乐曲. I don’t like the music. 16.你喜欢音乐吗 Do you like music 17.如果我是你, 我会跟他在一起.

雅思口语part2话题万能模板：事件类

雅思口语part2话题万能模板：事件类今天三立在线教育雅思网为大家带来的是雅思口语part2话题万能模板：事件类的相关资讯，备考的烤鸭们，赶紧来看看吧！ 首先我们来说说“一件从数学中学到的事情”，拿到这个话题，先不要急着回答，可以用笔稍微构思一下思路，该怎么回答。首先，可以说一下这件事是什么、发生在什么时候，也就是作文中的事件和事件，这里需要注意的就是具体描述一下什么事但是又不能啰嗦累赘，而时间则可以大致概括点明即可。我们就从资料中的例子来说：高中的时候从乘法表中学到的一件事。 然后，要具体叙述一下这件事，即是最重要的部分，发生的地方、牵扯到的人物、以及这件事情影响到你的原因，为什么影响到你…… 资料例子来说：在高中的一次数学竞赛中失败，以至于灰心丧气，甚至对自己产生怀疑，而此时数学老师拿乘法的规则来比喻人生中的失败与成功的关系来鼓励我，以至于我从失败中走出来，从新赢得了下一次的数学竞赛。这件事情使我明白了，生活就如同数学乘法，有无数种可能，多种多样，我们要坦然面对。 而这里的例子看似像我们中文作文中的思路，但是关键在于它表述方式以及用词造句，不能太中式化。这里的重点，就是描述事件经过，即“在高中的一次数学竞赛中失败，以至于灰心丧气，甚至对自己产生怀疑，而此时数学老师拿乘法的规则来比喻人生中的失败与成功的关系来鼓励我，以至于我从失败中走出来，从新赢得了下一次的数学竞赛。”而老师的话则是重中之重，因为他让我明白了道理“生活就如同数学乘法，有无数种可能，多种多样，我们要坦然面对。”也是我深深牢记的原因，以及这件事对我影响深刻的原因。

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高中英语每日一题第3周playapartin含解析新人教版必修120171011143

play a part (in) 重要程度：★☆☆☆☆难易程度：★★☆☆☆ Have you realized the part computers have ___________ in the daily life? A. made B. given C. caused D. played 【参考答案】D 【拓展延伸】 1. play a part (in) 在……中扮演一个角色；参与；在……中起作用 2. play the role of 扮演……的角色 play an important role / part in...在……中起重要作用 play the leading role / part主演；起带头作用 3. take part in 参加 for the most part多半；在很大程度上 for one’s part就某人而言，对某人来说 1. Colors play an important ___________ in the way you look. A. part B. form C. effect D. pride 2. Mr. Huang will ___________ in the movement. A. play a leading part B. take parts C. play leading part D. take a part 3. __________ part that women ___________ in society is great. A. The; plays B. A; takes C. A; plays

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playapartin的用法

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Audrey Hepburn played a leading part in directed by Steven Spielberg.( Always 直到永远/天长地久) play a part in…在……中扮演角色，在……中起作用

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medicine? 2019 E卷 Q1:英国人喜欢旧车吗？Do the British people like cars? Q2:你什么意思呢？What do you mean? Q3:英国人不太在乎穿什么衣服，对吗？ The British people care little about clothes, do they? 2012 A卷 Q1:你和你的室友相处得如何？How do you get along with your roommates? Q2:为什么你不直接与他们谈一谈？Why don’t you have a talk directly with them? Q3:你的老师的建议是什么？ What are yo ur teacher’s suggestions?/What is your teache r’s advice? 2019 B卷 Q1:我为什么不能与朋友们一起开车？Why can’t I drive with my friends? Q2:我真的需要这些规则吗？ Do I really need these rules? / Are these rules necessary for me? Q3:这些规则有什么用处？What are these rules for? / What’s the use of these rules? 2012 C卷 Q1:这本书有什么问题?What’s the problem of the book? Q2:为什么你认为情节难以相信？

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You mustn''t aim too high你不可好高骛远。 You''re really killing me!真是笑死我了! You''ve got a point there. 你说得挺有道理的。 Being criticized is awful !被人批评真是痛苦! 15 divided by 3 equals 5.15 除以3 等于5. All for one ，one for all.我为人人，人人为我。 East，west，home is best. 金窝，银窝，不如自己的草窝。 He grasped both my hands. 他紧握住我的双手。 He is physically mature.他身体已发育成熟。 I am so sorry about this. 对此我非常抱歉(遗憾)。 以上是三立在线老师带来的关于分享常用的雅思口语句型模版的详细内容，希望各位考生能从中受益，并不断改进自己的备考方法提升备考效率，从而获得理想的考试成绩。

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