# Lamport’s Scalar Clocks - PowerPoint PPT Presentation

1 / 12

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.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

Lamport’s Scalar Clocks

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

## 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.

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

• 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

• 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

Number of Processes

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

Number of Processes

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

Number of Processes

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

No. of Messages per process

Number of Processes

### 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

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

Running with high load of processes.

### References

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

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