COCOA(1/19) Real Time Systems LAB. COCOA MAY 31, 2001 김경임, 박성호

COCOA (1/19) Real Time Systems LAB.

COCOACOCOA

MAY 31, 2001김경임 , 박성호


Contents• Background• COCOA Overview• System Architecture• Key Technologies• Application Area• Evaluation• Conclusion• References


Background• A Thesis in Aerospace engineering, Pennsylvania

State Univ. by Anirudh Modi, 1999– “Unsteady separated flow simulations using a

cluster of workstations”

• Need to a suitable platform for the efficiency & accuracy of PUMA(a parallel flow solver) – Resolving several steady solutions– A fully three-dimensional unsteady separated flow

around a sphere

• PUMA : the Parallel Unstructured Maritime Aerodynamics

• Financial support : the Rotorcraft Center of Excellence(RCOE) at Penn State


COCOA Overview• The COst effective COmputing Array(COCOA)

• A Beowulf cluster that have 50 processors

• To bring low cost parallel computing– The whole system cost approximately $100,000 (1998 US dollars)

• Performance – the benchmark shows that was almost twice as fast

as the Penn State IBM SP (older RS/6000-370 nodes) supercomputer for this applications


System Architecture• Computing Node(26 WS-410 Dell W/S )

– Dual 400MHz Intel Pentium II Processors w/512K L2 Cache

– 512MB SDRAM– 4GB UW-SCSI2 Disk– 3com 3c509B 100Mbits/sec Fast Ethernet Card– 32x SCSI CD-ROM Drive– 1.44MB FDD– Cables

• In addition,– One Baynetworks 450T 24-way 100Mbits/sec Switch– Two 16-way Monitor/keyboard/mouse Switches– Four 500 kVa APC UPS – For one server : one monitor, keyboard, mouse and

54GB extra UW-SCSI2 HDD


System Architecture cont.

• Setting up H/W

Node1 Node2 Node3 Node25

Switch

Server

...


System Architecture cont.• Operating System

– RedHat Linux 5.1

• Software– Base packages from RedHat Linux 5.1,

Kernel#2.0.36– Freeware GNU C/C++ compiler(gcc, pgcc)– Fortran77/90 compiler & Debugger by Portland

Group– Freeware MPI libraries for parallel programming in

C/C++/Fortran77/90– ssh-1.2.26 for secure access– DQS v3.0, a queueing system– Scientific Visualization Software TECPLOT from

Amtec Corp.


Key Technologies• Beowulf Cluster

– A system which usually consists of one server node, and one or more client nodes connected together via Ethernet or some other fast network

– Developed for large scale computing, such as aerodynamics, atmosphere, physics, etc.

– First Developed at 1994 in NASA

– Low price supercomputing is possible• High performance/low price processors• High speed network devices available

– Numerous Beowulf clusters developed• Used in various computational science fields


Key Technologies cont.

• DQS (Distributed Queuing System)– Developed to experiment batch queuing system at the Super-computer Computations Research Institute,

Florida State Univ.– Provide a single coherent allocation and management

• MPI (Message Passing Interface)– Standard for parallel programming

• SSH (Secure Shell)– Program for logging & executing commands into/on a

remote machine– Provides secure encrypted communication inter-un-

trusted hosts over an insecure network


Application Area• Analysis maritime aerodynamics

– Analysis flows over complex configurations (like ships and helicopter fuselages)

– Use PUMA

– Details of problem:Helicopter can safely land on frigate in the North Sea only 10 percent of the time in winter


PUMA (Parallel Unstructured Maritime

Aerodynamics)

• Program for analysis of internal and external non-reacting compressible flows over arbitrarily complex 3D geometries

• Written entirely in ANSI C using MPI library for message passing and hence highly portable giving good performance



Aerodynamics) cont.• Use domain decomposition

– Domain decomposition• Distribute data across processes, and each process

performing approximately same operation on the data• Problem level parallelism, but loop level (not SIMD)• Minimize communications cost

– Functional decomposition• Divides a problem into several distinct tasks that may be

executed in parallel

• Parallelization in PUMA– Each compute node read its own portion of the grid file

at startup– Each compute node generate the flow solution over the

given grid, parallelly



Aerodynamics) cont.CAD Package,

GridTool, VGrid ...

Make grid

PUMA

Generates the flow solution over the given grid, parallellyand

combine the solution into a single file

toTecplot utility,Tecplot

Display the solution



Aerodynamics) cont.• Modifications to PUMA

– Modify PUMA to read several hundred lines at a time and broadcasting the combined data to every processor using a reasonably sized buffer

– Modify MPI to combine several small messages into one before starting communication

Mbits/sec vs Packet size on COCOA

for MPI_Send/Recv test



Aerodynamics) cont.

Improvement in PUMA performance after combining several small MPI messages into

one


Evaluation

Total Mflops vs Number of Processors on COCOA for PUMA

test case

Speed-up vs Number of Processors on COCOA for PUMA

test case


Evaluation cont.

NAS Parallel Benchmark on COCOA:comparison with other machines for Class “C” LU

test


Conclusion• Beowulf class supercomputer (PC, Linux, MPI, DQS, SSH)

• Cost effective supercomputer for numerical simulations– Almost twice as fast compared to the Penn State IBM-SP

supercomputer,for our production codes including PUMA, given the same number of processors, while being built at a fraction of the cost ($100,000(1998 US dollars)).

• Be suitable for only numerical simulation part (weather, fluid...) that doesn’t have high communication to computation ratios, because of the high communication latency.

• Good scalability with most of the MPI applications used

• The Object, to build Cost effective supercomputer for numerical simulations dealt with at Penn State has been fulfilled.


References• COCOA : http://cocoa.ihpca.psu.edu

• NAS Parallel Benchmarks : http://science.nas.nasa.gov/Software/NPB

• Beowulf : http://www.beowulf.org

• RedHat : http://www.redhat.com

• MPI : http://www.mcs.anl.gov/mpi

• DQS : http://www.scri.fsu.edu/~pasko/dqs.html

• Tons of references…

Documents

COCOA(1/19) Real Time Systems LAB. COCOA MAY 31, 2001 김경임, 박성호