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Architecture of Computing Systems (Lecture Notes in Computer ...

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Response Time (milliseconds)<br />

14<br />

12<br />

10<br />

8<br />

6<br />

4<br />

2<br />

Response Time<br />

Effect <strong>of</strong> the Degree <strong>of</strong> Neighborhood on Resource Discovery 185<br />

0<br />

0 10 20 30 40 50 60 70 80 90 100 110<br />

Degree <strong>of</strong> Neighborhood<br />

(a)<br />

Response Time (milliseconds)<br />

30<br />

25<br />

20<br />

15<br />

10<br />

5<br />

Response Time<br />

0<br />

0 1 2 3 4 5 6<br />

Number <strong>of</strong> Matchmaker<br />

Fig. 5. (a) Response time with vary<strong>in</strong>g the degree <strong>of</strong> neighborhood <strong>in</strong> the completely<br />

decentralized (P2P) approach. (b) Response time <strong>of</strong> centralized and multiple adaptive<br />

matchmakers approach.<br />

once the number <strong>of</strong> hops goes beyond 60 (Figure 5a). The over proportional<br />

<strong>in</strong>crease <strong>in</strong> response time is due to the communication overhead <strong>in</strong>curred with<br />

the <strong>in</strong>creased degree <strong>of</strong> neighborhood <strong>in</strong> the completely decentralized (P2P) ad<br />

hoc gird.<br />

We observe an <strong>in</strong>crease <strong>in</strong> the response time <strong>of</strong> multiple adaptive matchmakers<br />

approach with <strong>in</strong>creased number <strong>of</strong> matchmakers (Figure 5b). This<br />

<strong>in</strong>crease is due to the segmentation <strong>of</strong> the ad hoc grid and due to <strong>in</strong>creased communication<br />

as expla<strong>in</strong>ed <strong>in</strong> Section 5. The experiments were also executed under<br />

resource <strong>in</strong>tensive and task <strong>in</strong>tensive network conditions. We observed the same<br />

trend <strong>of</strong> the matchmak<strong>in</strong>g efficiency and response time as discussed above.<br />

It can be concluded from the above discussion that neither a completely<br />

centralized nor a completely decentralized (P2P) is generally a suitable <strong>in</strong>frastructures<br />

for resource discovery <strong>in</strong> an ad hoc grid. A completely centralized<br />

<strong>in</strong>frastructure is not scalable and can have a s<strong>in</strong>gle po<strong>in</strong>t <strong>of</strong> failure. On the other<br />

hand, a completely decentralized (P2P) <strong>in</strong>frastructure <strong>in</strong>curs excessive communication<br />

overhead that results <strong>in</strong> an <strong>in</strong>creased response time and decreased<br />

matchmak<strong>in</strong>g efficiency. An <strong>in</strong>termediate <strong>in</strong>frastructure hav<strong>in</strong>g multiple adaptive<br />

matchmakers seems most efficient <strong>in</strong> terms <strong>of</strong> response time and <strong>in</strong> f<strong>in</strong>d<strong>in</strong>g<br />

matches. The <strong>in</strong>termediate <strong>in</strong>frastructure with multiple adaptive matchmakers<br />

should be preferred whenever possible <strong>in</strong> the ad hoc grid.<br />

7 Conclusions<br />

In this paper, we analyzed the effect <strong>of</strong> vary<strong>in</strong>g the degree <strong>of</strong> neighborhood<br />

on resource discovery <strong>in</strong> a local ad hoc grid. For this purpose we def<strong>in</strong>ed and<br />

implemented the degree <strong>of</strong> neighborhood for participat<strong>in</strong>g nodes. Results were<br />

obta<strong>in</strong>ed for completely centralized, multiple adaptive matchmakers and for completely<br />

decentralized resource discovery approaches <strong>in</strong> an ad hoc grid. Results<br />

(b)

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