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Scalable Agent-based Modelling with Cloud HPC Resources for Social

Simulations

Peter Wittek – University of BorasXavier Rubio-Campillo – Barcelona Supercomputing Centre

Introduction

Computer simulation is increasingly used as a research tool in Humanities and Social Sciences projects

ABM is one the most promising tools, but its computing requirements can be high

HPC is the answer to this issue, but there are few applications of social simulation in these environments...

Why? What role plays Cloud Computing in the solution?

Agent-Based Modelling in Social Sciences

Inspired on SugarScape model

Two key concepts:Agent → individual entityEnvironment → cellular automata

The agent is defined by:Attributes defining its internal stateA “step” method containing predefined rules of behavior

ABM benefits & issues

ABM is attractive to social scientists because:Bottom-up approach to social phenomenaHeterogeneity and environment Advanced decision-making processesCloser to social science & humanities thinking

But we need to address some problems:Wrong understanding of what a model is (and is not)How to develop and understand a piece of software?How to analyze and share results?

ABM computational challenges

How can we distribute an execution in an efficient way?

Is possible to use more than 1 CPU/node?

How to serialize a constant rate of data without bottlenecks?

An example: distributing past societies

The requirements are diverse, given the broad scope of ABMWe need to address these challenges for different scenarios

i.e.: to model past societies we should take into account these properties:

Importance of environmentLow number of agentsIntensive local communication

How can we use this information to distribute the ABM?

The Pandora framework

Pandora is an open-source C++ framework developed to accomplish this task.Implementation & execution:

Automatic generation of code for parallel executionPython interfaceDistributed serialization (HDF5)

Analysis:GIS support (GRASS) & Statistical support (R package)Cassandra: an ABM visualization tool

Pandora workflow

Distributing the simulation

Order of execution

Breaking sequentiality

From:step()

To:updateKnowledge()selectAction()execute()updateState()

ABM in the cloud

HPC-CC is an interesting option because:ABM requires considerable computational powerSeveral Humanities/Social Sciences departments do not have access to HPC resourcesIt is difficult to share data

...but how this solution can impact the performance of an ABM framework like Pandora?

The experimental model

We will explore this problem with a model currently in use for archaeologists: gujaratSimThis ABM explores interactions between 2 populations competing for resources in a common environment:

hunter/gatherersPastoralists

Some details of gujaratSim are:Advanced decision making process (Markov Decision Process)Intensive use of enviromental data (biomass, water, etc.)Exploration of different population sizes

Infrastructures

The experiment will test 2 CC environments and a supercomputing infrastructure:

CC → Amazon Web ServicesEC2-regularEC2-clusterEC2-cluster unthrottled

Supercomputer → Mare NostrumEach node has 2 dual core IBM PowerPc 970 MP at 2.3 GhZMyrinet high-speed network

Performance experiments

We will test 2 different configurations with 2x2 and 3x3 nodes

CPU intensiveLow number of agentsIntensive MDP algorithm

Communication intensiveHigh number of agents'Wired' (rule-based) agent behavior

CPU intensive benchmark

Parallel efficiency

Load balance

CPU intensive MPI trace

Communication intensive benchmark

Parallel efficiency

Load balance

Communication intensive MPI trace

Conclusions

ABM is one of the most promising computational tools for investigating social phenomenaWe need to fulfill its computational requirements using HPCCloud-based HPC and multiplatform software are needed for this task

...can we develop GPU-based solutions?

...can we lower technical knowledge needed to develop distributed ABMs?

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Thank you!

There is a need for cloud HPC in social simulationPandora allows to deploy ABM in a cloud-based solutionSupercomputers and Cloud-HPC are complementary, given the diversity of problems to solve

xavier.rubio@bsc.es

If you are interested you can download Pandora from: http://github.com/xrubio/pandora