The Julia Language - RWTH Aachen Universityhpac.rwth-aachen.de/teaching/sem-lsc-13/Julia.pdf · “Julia has the performance of a statically compiled language while providing the

The Julia LanguageSeminar Talk

Francisco Vidal Meca

Languages for Scientific Computing Aachen, January 16, 2014

Why Julia?

Many languages, each one a trade-offMultipurpose language:

scientific computingmachine learningdata mininglarge-scale linear algebradistributed and parallel computing

"In short, because we are greedy. (We) want to have it all." [1]

The Julia Language 3

Julia and Scientific Computing

Julia is "A fresh approach to technical computing"

High level and highperformanceEasy syntaxParallelism & CloudcomputingGraphsFree and Open sourceDeveloped in the MITVersion 1.0 releasedFebruary 2012


About Julia

Multi-paradigmHomoiconicDynamicEasy integration with C/FortranMultiple-dispatchJust-in-time(JIT) LLVM-based compilerFree and open source

Core under MIT licenseLibraries under GPL, LGPL, BSDEnvironment under GPL

Numerical accuracy


Parallelism and Cloud computing

Key factor in Julia’s designBuilding blocks fordistributed computationMultiple worker processes

LocalRemote

Different from otherenvironments such as MPI

Built on remote referencesand remote callsSimplified with macros,e.g., @paralell

Examplefunction TicToc(N)

tic();nh = @parallel (+) for i=1:N

int(randbool())end;s=toc();println("Num. Heads: $nh ")println("in $s seconds")

end


Mathematical functions

Extensive Math function library

Integrates C and Fortran librariesLinear AlgebraRandom number generationSignal processingString processing


Integration

Calling external functions in C/FortranNeed to be Shared LibraryCalled directly with ccal

Exampleccal((:function,"library") ,RetType,InputTypes,Inputs)

julia> t = ccall( (:clock, "libc"), Int32, ())2292761

julia> t2292761


Performance

101

102

100

10-1

104

103

MatlabGo RMathematicaPythonFortran OctaveJavaScriptJulia

benchmark

fib

mandel

pi_sum

rand_mat_mul

rand_mat_stat

printfd

quicksort

parse_int

Figure: Benchmark times [1] relative to C 1.

1Smaller is better, C performance = 1.0


Plotting with Julia

Not in the core Julia System

Add-on package "Winston"

Julia and GNUplot

inset

−1

−0.5

0

0.5

1

0 1 2 3 4 5 6

−1

−0.5

0

0.5

1

0 1 2 3 4 5 6

Figure: Error bars and plotcomposition.


title!

−1

−0.5

0

0.5

1

Θi

0 2 4 6 8Σx2i

a points

b points

slope

0

20

40

60

80

100

0 20 40 60 80 100

title

x label

−1

−1/2

0

1/2

1

right

10 100 1000top

−1

−0.5

0

0.5

1

left

3 4 5 6 7 8 9bottom


Developer community

External packagesBuilt in package managerIJulia

Browser-based graphicalnotebook interfaceIPython and JuliacommunityE.g.: Prof. Edelman’snotes for the ParallelComputing class

Active communityMailing listGitHubYoutube channel“JuliaLanguage”StackOverflowUsers meetup (today inSan Francisco Bay Area). . .


http://beowulf.csail.mit.edu/18.337/calendar.html

http://beowulf.csail.mit.edu/18.337/calendar.html

Conclusion

Multi-purpose languageHigh level and easy syntaxHigh performanceGraphsParallelism & CloudcomputingIntegrationFree and Open Source

UsesBigFloats, Combinatorics,StatisticsLAPACK for Linear algebraSuiteSparse for SparsefactorizationsProvides BLAS functionswrappersSignal processing, FFTfunctions from FFTW


Conclusion


Example

function mandel(z)c = zmaxiter = 80for n = 1:maxiter

if abs(z) > 2return n-1

endz = z^2 + c

endreturn maxiter

end


Conclusion


101

102

100

10-1

104

103

MatlabGo RMathematicaPythonFortran OctaveJavaScriptJulia

benchmark

fib

mandel

pi_sum

rand_mat_mul

rand_mat_stat

printfd

quicksort

parse_int


Conclusion



Conclusion


Example

dzeros(100,100,10)dones(100,100,10)drand(100,100,10)dfill(x, 100,100,10)


Conclusion


Easy integration withCFortranShellPipes


So. . . what is Julia?

“Julia has the performance of a statically compiled languagewhile providing the interactive, dynamic experience andproductivity that scientists have come to expect....Julia is a game changer for high performance computing." [4]

Try Julia! Online Julia + tutorialhttp://forio.com/julia/repl/


http://forio.com/julia/repl/

References

Leah HansonShah, V.; Edelman, A.; Karpinski, S.; Bezanson, J.; Kepner, JThe Julia Language (Last accessed on Jan 2014)http://julialang.org

Leah HansonLearn Julia in Y minutes (Last accessed on Nov 2013)http://learnxinyminutes.com/docs/julia/

Douglas EadlineParallel Julia (Last accessed on Dec 2013)HPC - ADMIN Magazine http://www.admin-magazine.com/HPC/Articles/Parallel-Julia-Jumping-Right-In

Shah, V.; Edelman, A.; Karpinski, S.; Bezanson, J.; Kepner, JNovel algebras for advanced analytics in JuliaHigh Performance Extreme Computing Conference (HPEC), 2013


http://julialang.org

http://learnxinyminutes.com/docs/julia/

http://www.admin-magazine.com/HPC/Articles/Parallel-Julia-Jumping-Right-In

http://www.admin-magazine.com/HPC/Articles/Parallel-Julia-Jumping-Right-In

Demo and examples

See how Julia works:1 @parallel example and number of processors2 Alternating harmonic series approximation3 Plots

Feel free to ask!


Performance (2)

Figure: Benchmark times [1] relative to C.


IJulia

Figure: IJulia Screenshot


Debugging in Julia

Debugging is possible in JuliaNot integrated (yet) into the core language

Only guidelines to debug Julia’s C code in the FAQ section 2

Found some documentation about it in GitHubJulia Debugging Procedures using GDB 3

Prototype interactive debugger “Debug” as external package 4

2http://docs.julialang.org/en/latest/manual/faq3https://gist.github.com/staticfloat/61884184https://github.com/toivoh/Debug.jl


http://docs.julialang.org/en/latest/manual/faq

https://gist.github.com/staticfloat/6188418

https://github.com/toivoh/Debug.jl

The Julia Language - RWTH Aachen Universityhpac.rwth-aachen.de/teaching/sem-lsc-13/Julia.pdf · “Julia has the performance of a statically compiled language while providing the

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