Lamport s scalar clocks
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Lamport’s Scalar Clocks. Shiva Bottu. Organization. Introduction High level Implementation Details Experimentation Results Further Research. Introduction. Lamport’s logical clocks are introduced to capture causality relation in a distributed system.

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Lamport’s Scalar Clocks

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Lamport s scalar clocks

Lamport’s Scalar Clocks

Shiva Bottu


Organization

Organization

Introduction

High level Implementation Details

Experimentation

Results

Further Research


Introduction

Introduction

Lamport’s logical clocks are introduced to capture causality relation in a distributed system.

Each process Pi has a logical clock Ci and for a particular event a in P, it assigns an integer value Ci, which is timestamp of the event.

Timestamps are monotonically increasing.


High level implementation details

High level Implementation Details

  • There are 2 implementation rules that should be followed

  • Before executing event, update timestamp value

    Ci:=Ci+d

  • When sending a message, attach the timestamp. When message is received by a process, timestamp of receive event is calculated as maximum of the two timestamps (timestamp of the process and timestamp received in the message)

    Ci:=max(Ci,Cmsg)


Experimentation

Experimentation

  • Number of processes are varied.

  • Random flood algorithm is used to exchange messages between processes

  • Part 1:

    • Total number of updates are plotted against number of processes

    • Average number of updates per process against number of processes

  • Part 2:

    • Number of updates and Number of messages against number of processes

    • Number of processes against average number of messages required for each process


Part 1 a total clock updates against number of processes

Part 1(a):Total clock updates against Number of processes

Number of clock updates

Number of Processes


Part 1 b average clock updates per process against number of processes

Part 1(b):Average clock updates per process against Number of processes

Average clock updates

Number of Processes


Part 2 a no of processes vs clock updates no of processes vs no of messages required

Part 2(a): No. of Processes VS clock updates & No. of Processes VS No. of messages required

clock updates & Messages

Number of Processes


Part 2 b no of processes vs average no of messages per process

Part 2(b): No. of Processes VS Average no. of messages per process

No. of Messages per process

Number of Processes


Results

Results

From part-1(a), it is observed that the number of updates increase with increase in number of processes

From part-1(b), average number of updates per process increase with increase in number of processes

From part-2(a), we can observe that number of clock updates and number of messages increase with increase in no. of processes

From part-2(b), we can observe that average number of messages required per process increases with increase in number of processes


Further research

Further Research

To change the base algorithm from random flood to other topologies and test with the same process.

Running with high load of processes.


References

References

http://en.wikipedia.org/wiki/Lamport_timestamps

http://cnlab.kaist.ac.kr/~ikjun/data/Course_work/CS642-Distributed_Systems/papers/lamport1978.pdf


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