Showing posts with label software engineering. Show all posts
Showing posts with label software engineering. Show all posts

Thursday, March 19, 2015

Introduction to Julia

"Julia is a fresh approach to technical computing."  boasts the startup message, flourished with colorful circles hovering above a bubbly ASCII Julia logo.  The formatting effort is not wasted, it's an exuberant promise: Julia will make the command line fun again.
apptrain_1@julia:~/workspace $ julia
   _       _ _(_)_     |  A fresh approach to technical computing
  (_)     | (_) (_)    |  Documentation:
   _ _   _| |_  __ _   |  Type "help()" to list help topics
  | | | | | | |/ _` |  |
  | | |_| | | | (_| |  |  Version 0.2.1 (2014-02-11 06:30 UTC)
 _/ |\__'_|_|_|\__'_|  |  
|__/                   |  x86_64-linux-gnu


Julia was created by four Data Scientists from MIT who began working on it around 2011.  The language is beginning to mature at a time when the Data Scientist job title is popping up on resumes as fast as Data Scientist jobs appear.  The timing is excellent.   R programming, an offshoot of S Programming , is the language of choice for today's mathematical programmer.  But it feels clunky, like a car from the last century. While Julia may not unseat R in the world of Data Analysis,  plans don't stop there.

If you want to code along with the examples in this article, jump to Getting Started with Julia and chose one of the three options to start coding.

Julia is a general purpose programming language.  It's creators have noble goals.  They want a language that is fast like C, they want it flexible with cool metaprograming capabilities like Ruby, they want parallel and distributed computing like Scala, and true Mathematical equations like MATLAB.

Why program in Julia?

1) Julia is Fast

Julia already boasts faster matrix multiplication and sorting than Go and Java.  It uses the LLVM compiler, which languages like GO use for fast compilation.   Julia uses just in time (JIT) compilation to machine code , and often achieves C like performance numbers.

2) Julia is written in Julia

Contributors need only work with a single language, which makes it easier for Julia users to become core contributors. 
"As a policy, we try to never resort to implementing things in C. This keeps us honest – we have to make Julia fast enough to allow us to do that" -Stephan Karpinski

And, as the languages co-creator Karpinski notes in the comments of the referenced post,   Writing the language itself in Julia means that when improvements are made to the compiler, both the system and user code gets faster.

3) Julia is Powerful

Like most programming languages, it's implementation is Open Source.  Anyone can work on the language or the documentation.  And like most modern programming languages, Julia has extensive metaprogramming support.  It's creators attribute the Lisp language for their inspiration:
Like Lisp, Julia represents its own code as a data structure of the language itself.
a) Optional Strong Typing
Using strong typing can speed up compiling, but Julia keeps strong typing optional, which frees up programmers who want to write dynamic routines that work on multiple types. 
julia> @code_typed(sort(arry))
1-element Array{Any,1}:
 :($(Expr(:lambda, {:v}, {{symbol("#s1939"),symbol("#s1924")},{{:v,Array{Float64,1},0},{symbol("#s1939"),Array{Any,1},18},{symbol("#s1924"),Array{Any,1},18}},{}}, :(begin $(Expr(:line, 358, symbol("sort.jl"), symbol("")))
        #s1939 = (top(ccall))(:jl_alloc_array_1d,$(Expr(:call1, :(top(apply_type)), :Array, Any, 1))::Type{Array{Any,1}},$(Expr(:call1, :(top(tuple)), :Any, :Int))::(Type{Any},Type{Int64}),Array{Any,1},0,0,0)::Array{Any,1}
        #s1924 = #s1939::Array{Any,1}
        return __sort#77__(#s1924::Array{Any,1},v::Array{Float64,1})::Array{Float64,1}

b) Introspective

Julia's introspection is awesome, particularly if you enjoy looking at native assembler code. Dissecting assembler code comes in handy when optimizing algorithms. Julia programmers have several introspection functions for optimization. Here the code_native method shows the recursive nature of a binary sort algorithm.
julia> code_native(sort,(Array{Int,1},))
        push    RBP
        mov     RBP, RSP
        push    R14
        push    RBX
        sub     RSP, 48
        mov     QWORD PTR [RBP - 56], 6
        movabs  R14, 139889005508848
        mov     RAX, QWORD PTR [R14]
        mov     QWORD PTR [RBP - 48], RAX
        lea     RAX, QWORD PTR [RBP - 56]
        mov     QWORD PTR [R14], RAX
        xorps   XMM0, XMM0
        movups  XMMWORD PTR [RBP - 40], XMM0
        mov     QWORD PTR [RBP - 24], 0
        mov     RBX, QWORD PTR [RSI]
        movabs  RAX, 139888990457040
        mov     QWORD PTR [RBP - 32], 28524096
        mov     EDI, 28524096
        xor     ESI, ESI
        call    RAX
        lea     RSI, QWORD PTR [RBP - 32]
        movabs  RCX, 139889006084144
        mov     QWORD PTR [RBP - 40], RAX
        mov     QWORD PTR [RBP - 32], RAX
        mov     QWORD PTR [RBP - 24], RBX
        mov     EDI, 128390064
        mov     EDX, 2
        call    RCX
        mov     RCX, QWORD PTR [RBP - 48]
        mov     QWORD PTR [R14], RCX
        add     RSP, 48
        pop     RBX
        pop     R14
        pop     RBP

c) Multiple Dispatch

Multiple dispatch allows Object Oriented behavior.  Each function can have several  methods designed to operate on the types of the method parameters. The appropriate method is dispatched at runtime based on the parameter types.

julia> methods(sort)
# 4 methods for generic function "sort":
sort(r::UnitRange{T<:real at="" bstractarray="" dim::integer="" pre="" r::range="" range.jl:533="" range.jl:536="" sort.jl:358="" sort.jl:368="" sort="" v::abstractarray="">

Wednesday, August 6, 2014

Using the Chromebook for Software Development

Recently I compared two nice chromebooks. The Acer 720P  and the HP 11.  Both laptops sell for around $200. I ended up buying the Acer because it has a touchscreen, and the  Haswell processor which has a long battery life.  The HP 11 would have been a great choice too, because it is so lightweight at 2.3 pounds, and charges with a standard USB charger, which would have lightened my travel bag even further.

Since then I've been using the Chromebook as my main software development machine. There are two reasons this works.

1)  Cloud Applications

The best software now runs in the cloud.

Cloud based Integrated Development Environments (IDEs) are the present and future of software development.   You can even share configurations across multiple users.  I work on some legacy projects where up to 80% of developers time is spent on configuring things like Environment Variables on the desktop. With the Cloud IDE,  repeating this nightmare for every new desktop is a thing of the past.

Fantastic utilities like Pixlr for quick graphic design, Google Drive for collaborative documentation,  Trello for task management and Bitbucket for source control make cloud developers instantly productive and happier.

2) Legacy Support

Not every software project is on the cutting edge.   When I need a specific desktop environment such as Windows, I rely on virtual machines to provide me that environment instantly.  Amazon Web Services is the pioneer in making endless resources available to Software Developers.  Their Free usage tier is a must for any engineer.  VMWare, Virtualbox and Windows Azure have also begun to provide virtual machines (VMs) in the cloud.

A hackers paradise

When it's time to play behind the scenes of the operating system,  Linux is a frequent choice.  Thanks to Crouton, You can now have an Ubuntu instance accessible from the Chrombook shell.   I already have legacy java projects running on my linux instance.  I work there when I don't want to utilize cloud resources. Linux is also great for running desktop software that can't be accessed from the cloud, such as the Kerbal Space Program, where I get to spend time above the clouds.

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