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Computational Steering on the GRIDUsing a 3D model to Interact with a Large Scale

Distributed Simulation in Real-Time

Michael Grønager, PhD

UNI-C / Virtual Reality Center

Present: Niels Bohr Institute

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Overview

• The GRID in 7 minutes…• Computational Steering• Examples:

• Interactive Molecular Dynamics• Interactive Fluid Dynamics

• OpenLB – an open source Lattice-Boltzmann solver

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A quick example

• Use Private Certificate to generate a time limited “Proxy”• Log in to the Grid• Define a job:

• /bin/echo “Hallo Grid”

• (demo)

• Wait for completion…

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The GRID

• What is: “The Grid”?- except for a Buzz word…

• Analogy: “The Electrical Power Grid”

• The Globus Toolkit

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Quoted from globus.org

The Grid refers to an infrastructure that enables the integrated, collaborative use of high-end computers, networks, databases, and scientific instruments owned and managed by multiple organizations. Grid applications often involve large amounts of data and/or computing and often require secure resource sharing across organizational boundaries, and are thus not easily handled by today’s Internet and Web infrastructures.

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CERN

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Storage – Raw recording rate 0.1 – 1 GBytes/sec

Accumulating at 5-8 PetaBytes/year

10 PetaBytes of disk

Processing – 200,000 of today’s fastest PCs

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NorduGrid

• A Scandinavianproduction Grid

• More than 2200CPUs• More than 30 sites

• (Grid monitor demo)

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Angio w/ Fem-Fem &Fem-Pop

AFB w/ E-S Prox.

Anast.

Angio w/Fem-Fem

AFB w/ E-E Prox.

Anast.

Preop

Computational Steering

• The ability to interact with a simulated physical model by changing border conditions, parameters or state.

• This means:• Fast interaction times < 10s• Intuitive user interface• Physical representation of the data

• And to get this we need:• Interactive parallel algorithms• Lots of computers with fast network• A lot of money or…• …resource sharing

• The perfect candidate for the GRID!

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Example: Interactive Molecular Dynamics

• VMD / NAMD 1 ported to GRID environments• … Lets start the job …• Setup:

• Client contacts Resource Broker• A worker node (or cluster) is selected to match requirements• Job is submitted

• Opens a SSH tunnel back to Client (this Laptop) using Private/Public keys

• Starts NAMD• Client starts VMD• Connects to tunneled port

• Steering established

• 1. See: University of Illinois at Urbana-Champaign: http://www.ks.uiuc.edu

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Interactive Fluid Dynamics• Traditional Navier-Stokes solvers not meant for interaction:

• Important (manual) preprocessing step building an optimal mesh.• Hard to parallelize• No Open Source code available

• The alternative: Lattice-Boltzmann Method• Easy to change border conditions on the fly• Easy to parallelize• No Open Source code available – yet …• … easy to implement

• OpenLB• True 3D Lattice Boltzmann solver• Uses ParaView for interaction and data visualization• Uses OpenSceneGraph for Virtual Reality interface

• Aim is to run OpenLB interactively on the GRID on more than 1000CPUs

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Questions?

• Sign up for a hands on Grid tutorial Tuesday the 8th of June 15.30-18.00 at the Niels Bohr Institute.Mail to: mpg@uni-c.dk / waananen@nbi.dk