Agent-based Model Simulationwith Twister

Bingjing Zhang, zhangbj@indiana.edu

Lilian Weng, weng@indiana.edu

B649 Term Project Presentation

Problem Statement

• Run the agent-based modeling (ABM)[1] simulation in parallel.

• Reason: Sequential iterations on a single machine are too slow

[1] E. Bonabeau. Agent-based modeling: Methods and techniques for simulating human systems.

Proceedings of the National Academy of Sciences, 99:7280–7287, 2002.

Experiment

• A model simulating Twitter mechanism:– Users are connected through the social network– Each user has a screen of messages from neighbors,

and a memory of topics he is interested in.– Users send messages chosen from screen or memory

C - capacity of the screen and memory.Pn - probability to introduce a new topic.Pr - probability to re-post a message from the screen.α - the priority of topics in the memory compared to the screen messages, and therefore the probability of posting about the memory topics is αPr.

ArchitectureDesign of the Application

Broadcasting on Twister

• Broadcasting– Chain Broadcasting– All-to-all Minimum-spanning Tree

Chain Broadcasting Protocolsend

get ack

send

Driver Daemon 0receive

handle data

send

Daemon 1

ack receive

handle data

send

ack

receive

handle data

get ack

ack receive

handle data

get ack

send

send

get ack

Daemon 2

receive

handle data

ack

receive

handle data

ack

ack

get ack

get ack

“Handle data” is done by spawning another thread

“Send” and “Receive” are done in a manner of “buffer by buffer”

MST broadcasting

Driver sends data portions to different nodes

MST Leaf Node

MST Root Node

Twister Driver

All-to-all-MST Broadcasting Protocal

MST Broadcasting Protocol

[3] Ernie Chan et, al. Collective Communication: Theory, Practice, and Experience. Concurrency and

Computation: Practice and Experience. 2007

Implementation: Model Classes

Implementation: TwisterMessagepublic void fromTwisterMessage(TwisterMessage message) throws SerializationException {

message.writeInt(a);…

}

public void toTwisterMessage(TwisterMessage message) throws SerializationException {

this.a = message.readInt();…

}

Results: Broadcasting Efficiency 80 PG nodes, 2 switches, 50 Iterations, Data Size(Each Iteration) 200KB ~ 200MB, Data

Size(Total) 1GB ~ 5GB

Results: Simulation Result Validation

Memory Length – number of topics in memoryTopic Popularity – number of distinct user who have used a certain topicTopic Prevalence – number of posts containing a certain topic

Thank you! Question?