# Presentation: 354174

## An application-based measureof cluster success Mark L. Sawley Visiting Scientist:  EPF-Lausanne, SwitzerlandPermanent address:  CSIRO Mathematical & Information Sciences, Australia

- Presented at the 4th Workshop on Distributed Supercomputers,
- New Orleans, March 9-10, 2000

## Measure of cluster success

- Question:
- 		What is the best measure of success of a general-purpose 		central distributed supercomputer (cluster) system?
- (One) Answer:
- 		A wide application community,
- 		not just a small number of heavy users
- This measure is very stringent and is comprised of more conventional
- aspects, such as performance and availability.

## Who are the potential users?

- An abbreviated history of central parallel machines at the EPFL:
- 		1986	Cray 1 (2 proc.)
- 		1988	Cray 2 (4 proc.)
- 		1994	Cray Y-MP (4 proc.)  +  Cray T3D (256 proc.)
- 		1996	SGI Origin2000 (80 proc.)
- 		1998 	Swiss Tx (8  70 proc.)
- Potential EPFL cluster community origins:
-   vector (Crays, NEC)
-   distributed memory massively parallel (Cray T3D)
-   NUMA (SGI Origin2000)
-   workstation

## Classification of users

- Require “early adapters” to encourage use by “conservative users”
- otherwise number of users will be limited.

## “Technology enthusiasts”

- Characteristics:
- not interested in application results
- main interest in future technology
- Needs:
- a system (containing hardware + software)
- performance irrelevant
- no additional software required
- access to system gurus
- sufficient time (between machine crashes)

## “Early adapters”

- Characteristics:
- interested in application results
- willing to invest in future technology
- Needs:
- robust system (hardware + software)
- good performance
- minimum amount of software (MPI, BLAS, ....)
- basic level of user support
- dedicated time (for benchmarking)

## “Conservative users”

- Characteristics:
- only interested in application results
- not willing to invest in future technology
- Needs:
- user-friendly system (looks like presently-used system)
- excellent performance (better than presently-used system)
- extensive software (debugging, visualisation, commercial codes, ...)
- high level of user support
- sufficient machine access (to complete large-scale applications)

## Examples of “early adapters” of the Swiss-T1

- Computational Fluid Dynamics–  *nsmb* (multi-block, finite volume)–  *fluent* (unstructured, finite volume)
- 	–  *speculoos* (object-oriented, spectral element)
- Granular flow
- 	–  *gfc* (discrete element method)
- Molecular Dynamics
- 	–  *lautrec* (Carr-Parrinello method)
- Structural analysis
- 	–  *crash* (object-oriented, finite element)
- Plasma transport
- 	–  *orb* (particle-in-cell, finite element)

## Examples of “conservative users”

- Two classes:
- Users porting their own codes–  need a lot of user support
- Users of existing parallel codes
- 	–  in-house
- 	–  commercial
- At the EPFL, these users can potentially come from any of the
- 11 different departments (ranging from Mathematics to Architecture).
- Both classes can be encouraged by benchmark results.

## Example of a commercial code benchmarks

*Fluent CFD code:* Suite of 9 different test cases of different size and
-                                 physical complexity (eg turbulence, combustion)

- Small class
- < 100,000 cells

- Medium class
- 100,000 – 500,000 cells

- Large class
- > 500,000 cells

- Full details: www.fluent.com/software/fl5bench

## Computational Fluid Dynamics (nsmb)

*Code:  nsmb* is a 2D/3D multi-block compressible flow solver
*Personnel:*  Jan Vos (EPFL)

## Computational Fluid Dynamics (nsmb)

- AS28G full aircraft configuration, using mesh:

- 62 unequal blocks
- 3.5 million cells
- (~ 2 GB memory required)

## Computational Fluid Dynamics (fluent)

*Code:  fluent* is a commercial 2D/3D unstructured flow solver
*Personnel:*  Mark Sawley (EPFL/CSIRO)

- Kenics static mixer

## Computational Fluid Dynamics (fluent)

## Granular flow (gfc)

*Code:  gfc* is a 2D/3D Discrete Element Method code
*Personnel:*  Mark Sawley & Paul Cleary (CSIRO)

- Hicom nutating mill

- Flow from a two-port hopper

## Granular flow (gfc)

## Molecular Dynamics (lautrec)

*Code:  lautrec* is a first-principles MD code using Carr-Parrinello method
*Personnel:*  Alessandro De Vita, Massimiliano Stengel (EPFL)
- 		   Andrew Canning, Roland Richter (SGI/Cray Research)

- DNA molecule

- bovine pancreatic
- trypsin inhibitor

- diamond-graphite
- transition

## Molecular Dynamics (lautrec)

- Performance results on Swiss-T1 baby machine using MPI on T-Net.

*big system*
- 32 water molecues
- cell dimension: 18.64 a.u.
- cut-off energy: 90 Ry
- FFT grid: 112x112x112
*medium system*
- 32 water molecules
- cell dimension: 18.64 a.u.
- cut-off energy: 30 Ry
- FFT grid: 64x64x64
*small system*
- 108 aluminium atoms
- cell dimension: 22.92 a.u.
- cut-off energy: 10 Ry
- FFT grid: 48x48x48

## Conclusion of preliminary benchmarks

- The initial timing results of application codes on the Swiss-T1 show:
- good overall performance due to Alpha ev6 processor
- good scalability up to the 12 processors available on the prototype Swiss-T1 baby
- substantially better scalability for communication-intensive applications using T-Net compared to Fast- or Giga-Ethernet