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## PowerPoint Slideshow about 'Orderly Broadcasting in Multidimensional Tori' - medwin

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Presentation Transcript

Outline

- Introduction and Motivation
- Types of Broadcasting
- Orderly Broadcasting
- Lower Bound on 2-dimensional Tori
- Upper Bound for 2-dimensional Tori
- Upper Bound for d-dimensional Tori
- Conclusion and Future Work

Introduction

Broadcasting : process of sending a message from one node of a communication network to the rest of the nodes.

Originator: the node of the network which initiates broadcasting by sending its message to the rest of the nodes.

Broadcast problem : the problem of determining the amount of time needed to transmit a message to every node in an interconnection network

Motivation

- Computer networks
- Parallel processing
- Cache coherence

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ConstraintsBroadcasting is subject to the following constraints:

- Each message transmission takes 1 time unit
- A node can transmit only to an adjacent node
- A node can transmit a message to 1 node in 1 time unit

Types of Broadcasting

Broadcast models can be divided into two major categories:

- Classical Broadcasting (Slater in 1977)
- Messy Broadcasting (Alshwede, Khatchadrian & Harutyunyan in 1994)

Notations

A network is modeled as a connected graph G=(V, E)

b(u) : min number of time units required to complete broadcasting when u is the originator (classical)

bm(u): max number of time units required to complete broadcasting when u is the originator (messy)

b(G) = max {b(u) | u V}

bm(G) = max {bm(u) | u V}

Classical Broadcasting

Find a scheme so as information dissemination takes the least amount of time.

Assumption: each vertex knows the

- graph topology
- originator of the message
- time the message was sent.

When a vertex is informed, it transmits the message to its neighbor in the most cleverway.

Messy Broadcasting

Analyzes broadcast schemes that take the mostamount of time

Assumption: each vertex knows nothing about the graph topology and the originator.

When a vertex is informed, it transmits the message to a randomly chosen neighbor in each time unit.

How hard is it?

Finding b(u) for an arbitrary graph isNP-Complete

Practicality

Storing information about the graph topology and the originator is not efficient in practice

Sometimes, network nodes have primitive structures with small memories that cannot store such information.

Building networks where the vertices have no decision making responsibility is easier.

Orderly Broadcasting

The neighbors of each vertex are assigned a unique number.

Assumption: each vertex knows nothing about the graph topology and the originator.

When a vertex is informed, it transmits the message first to vertex numbered 1, then to vertex numbered 2, …etc.

Orderly Broadcasting

Problem:

Find an orderingof the neighbors of all the vertices of a given graph that will minimize the broadcast time.

2-dimensional Tori

Torus Tmn: wrap-around grid with m rows & n columns

Each vertex in a 2-dimensional torus has degree 4

Diameter of Tmn is :

Every vertex in Tmn has : 1 vertex at distance D(Tmn) if m and n are even 2 vertices at distance D(Tmn) if one of m or n is odd 4 vertices at distance D(Tmn) if m and n are odd

A 2-dim Torus

Torus T69

How it works: an example T813

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How it works: an example T813

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Conclusion and Future Work

- Improve the upper and lower bound
- Find orderings for other graph types – for example Butterfly BFm, Shuffle-Exchange SEm, DeBruijn DBm, Cube-Connected Cycles CCCm, …etc)
- Study the relationship between the Classical, Messy and Orderly broadcast models.

The End

Thank You !

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