Copyright, HiPERiSM Consulting, LLC, George Delic, Ph.D. HiPERiSM Consulting, LLC (919)484-9803...

Copyright, HiPERiSM Consulting, LLC, http://www.hiperism.com

George Delic , Ph.D.

HiPERiSM Consulting, LLC

(919)484-9803

P.O. Box 569,

Chapel Hill, NC [email protected]

http://www.hiperism.com

HiPERiSM Consulting, LLC.


CHOOSING A COMPILER FOR AQM APPLICATIONS ON LINUX

George Delic, Ph.D.

Models-3 User’s WorkshopOctober 27-29, 2003

RTP, NC


Overview

1. Introduction2. Choice of Hardware3. Choice of Compilers4. Choice of Benchmarks5. Comparing Execution Times6. Evaluation of SSE Results7. Tests for AQM’s8. Conclusions


Introduction

MotivationAQM’s are migrating to COTS hardwareLinux is preferredRich choice of compilers is now availableNeed to learn about portability issues

What is known about compilers for IA-32?CMAQ releases switch compilers w/o commentWhere is the analysis of differences in

Performance?Numerical accuracy & stability?Portability problems?


Choice of Hardware & Compilers

HardwareIntel Pentium III (933 MHz, dual processor) with

SSE extensions and 256MB L2 cacheLinux 2.4.20 kernel

Fortran compilers for IA-32Absoft 8.0Intel 7.1Lahey 5.6Portland CDK 4.0


Choice of Benchmarks

Kallman Integer and Logical AlgorithmUses only I & L operations with bit intrinsicsNegligible I/O and memory operationsSix cases with problem size scaling

Stommel Ocean Model sp Floating Point AlgorithmJacobi iteration sweep over 2-D physical

domainRegular loops optimal for testing vectorizationSix cases in the range N=2x103 to 7x103 with

N2=4 to 49 million data points


Choice of Benchmarks (cont.)

Princeton Ocean Model dp FP AlgorithmExample of “real-world” code that is

numerically unstable with sp arithmetic! 500+ vectorizable loops to exercise compilers9 procedures account for 85% of CPU time 2-Day simulation for two cases:

Small problem: 65 x 49 x 21 Large problem: 100 x 40 x 15


Comparing Execution Times: Kallman compiler switches

Compiler and version

Compiler command and selected switches

Absoft 8.0 f90 –O3 –ffixed

Intel 7.1 ifc –O3 –tpp6 -FI

Lahey 5.6 lf95 –tpp –fix

Portland 4.0 pgf90 –fast


Comparing Execution Times: Kallman (seconds)

N Absoft Intel Lahey Portland

30 0.21 0.36 0.48 0.60

44 40.38 80.19 98.45 135.29

48 6.44 13.15 16.16 22.52

52 23.03 48.20 59.30 83.28

56 197.78 412.83 509.31 712.42

60 12891.58 26734.09 32833.08 45451.38


Comparing Execution Times: Kallman (log10 seconds)

Kallman Integer & Logical Algorithm (PIII 933 MHz)

-1

0

1

2

3

4

5

1 2 3 4 5 6

Case

Lo

g1

0 o

f w

all

tim

e (

se

co

nd

s)

Absoft

Intel

Lahey

Portland


Comparing Execution Times: Kallman (ratio to Absoft time)

Kallman Integer & Logical Algorithm (PIII 933 MHz)

0

0.5

1

1.5

2

2.5

3

3.5

4

1 2 3 4 5 6

Case

Ra

tio

to

Ab

so

ft t

ime

Intel / AbsoftLahey / AbsoftPortland /Absoft


Comparing Execution Times: SOM (POM) compiler switches

(without SSE)Compiler and version


Absoft 8.0 f90 –s –cpu:p6–O3 (-N113) –ffixed

Intel 7.1 ifc –O3 (-r8) –tpp6 -FI

Lahey 5.6 lf95 –tpp (-dbl) –fix

Portland 4.0 pgf90 –fast (-r8) –Mvect


Comparing Execution Times: SOM without SSE (seconds)

N Absoft Intel Lahey Portland

2000 50.0 38.8 36.4 41.4

3000 110.5 94.4 87.7 92.7

4000 197.7 159.6 150.3 163.3

5000 305.3 224.3 246.8 253.1

6000 443.4 320.0 332.0 388.5

7000 586.5 427.6 477.9 524.4


Comparing Execution Times: SOM (without SSE)

SOM Floating Point Algorithm (PIII 933 MHz)

0

100

200

300

400

500

600

700

1 2 3 4 5 6

Case

Wa

ll t

ime

(s

ec

on

ds

)

AbsoftIntelLaheyPortland


Statistics for four compilers: SOM (without SSE)

SOM Floating Point Algorithm (PIII 933 MHz): Statistics for four compilers

0

100

200

300

400

500

600

1 2 3 4 5 6

Case

Wa

ll t

ime

(s

ec

on

ds

)

Mean

StandardDeviationCoefficient ofVariation x 1000


Comparing Execution Times: POM (without SSE)

POM Floating Point Algorithm (PIII 933 MHz)

0100200

300400500600700

800900

1000

1 2

Case

Wa

ll t

ime

(s

ec

on

ds

)

AbsoftIntelLaheyPortland

Case Absoft Intel Lahey Portland

1 909.1 826.4 728.8 836.3

2 825.1 786.9 671.2 755.3


Statistics for four compilers: Variability vs. problem size

Coefficient of Variation for four compilers(PIII 933 MHz, without SSE)

00.05

0.10.15

0.20.25

0.30.35

0.40.45

0.5

1 2 3 4 5 6

Case

Sta

nd

ard

De

via

tio

n /

Me

an

KallmanSOMPOM


Evaluation of SSE Results

IA-32 HardwareIntel Pentium III+ supports Streaming-

Single-Instruction-Multiple-Data Extensions (SSE)

Linux 2.4.20 kernel supports SSE

Fortran compilers that enable SSEIntel 7.1Portland CDK 4.0


Comparing Execution Times: SOM (POM) compiler switches

(with SSE)

Compiler and version


Intel 7.1 ifc –O3 -xK (-r8) –tpp6 -FI

Portland 4.0 pgf90 –fast (-r8) –Mvect=sse


Comparing Execution Times: SOM (with SSE)

SOM Floating Point Algorithm (PIII 933 MHz)

0

100

200

300

400

500

600

1 2 3 4 5 6

Case

Wa

ll t

ime

(s

ec

on

ds

)

IntelIntel (SSE)PortlandPortland (SSE)


Comparing Execution Times: POM (with SSE)

POM Floating Point Algorithm (PIII 933 MHz)

0

100

200

300

400

500

600

700

800

900

1 2

Case

Wa

ll t

ime

(s

ec

on

ds

)

IntelIntel (SSE)PortlandPortland (SSE)


Evaluation of SSE Results

Fortran compilers with SOM (sp)Intel 7.1

Average speed up of 1.44

Portland CDK 4.0Average speed up of 1.70

Fortran compilers with POM (dp)Intel 7.1

Average speed up of 1.25

Portland CDK 4.0Average speed up of 1.19


Tests for AQM’s

Next steps for CMAQ with four compilers:• Report on portability issues• Re-compilation of all libraries• Performance instrumentation & analysis• Numerical & stability analysis• OpenMP performance study

Please propose scenarios worthwhile using for these tests!


Conclusions

Hardware: COTS is the way to go but ……. Linux: Operating System is popular but ….. Programming Environment: rich in choices Consequences for AQM: the combination

of hardware, Linux, and programming environment needs careful on-going evaluation.

HiPERiSM is ready for this task!


HiPERiSM’s URL

http://www.hiperism.com

Talk to us about your requirements

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