Trends inProgramming LanguagesBart J.F. De Smetblogs.bartdesmet.net/bartbartde@microsoft.com

DEMOThe Good Old Days?

Looking at the Past…

Assembler

Procedural

ObjectsManaged

Richer RuntimesEase of Use

More ControlToo low-level

Hardware Trends

x 10,000

x 100,000

x 1,000

What aboutSSD?

What about NUMA?

What aboutmany-core?

Aim Higher or Lower?

Higher Levels of Abstraction• Richer Frameworks (e.g. .NET)• Language Innovation (e.g. C#)• Improved Expressiveness (e.g. FP)

Low-Level Plumbing

Can we avoid the disconnect?

• Machine Architectures (e.g. ARM)• Power Consumption (e.g. phone)• Rich Capabilities (e.g. GPU)

Two Stories on Bridging the Gaps

GPU Acceleration Asynchronous I/O

Win32 APIs

Common Language Runtime

Task Parallel Library

C# and VB vNext

DirectX APIs

Internet Explorer 9 Rendering

HTML 5

Canvas

User

System

Established Reality!Rocket Science?

Time

Software Trends

8

• Horse-power of many-core…• …but how to program those?Concurrent

• Say what you want…• …not how it has to be done?Declarative

• Schematized, static, dynamic…• …so, what’s the sweet spot?Dynamic

• New level of expressiveness…• …how about the essence?FunctionalBut w

ill it

ble

nd?

FUNCTIONAL PROGRAMMINGIncreasing the level of abstraction

A Different Approach

Theory of Computation(Lambda Calculus, Alonzo Church)

LISP Heritage

Reality of Hardware(Memory, John Von Neumann)

Fortran Heritage

Basi

c

SmallTalk

ModulaC C++Java

C#

Sche

me

SASLHaskell

ML

Miranda

CLU

Lambda Expressions are All Around Us

var res = xs.Where(x => x % 2 == 0);C#

Dim res = xs.Where(Function(x) x Mod 2 = 0)Visual Basic

let res = xs |> Seq.filter (fun x -> x % 2 = 0);F#

var res = xs.filter(function(x) { return x % 2 == 0;});

JavaScript

auto res = find_if(xs.begin(), xs.end(), [] (int i) { return x % 2 == 0;});

C++0x

Have We Forgotten About Math?

x = x + 1

Defining Functions

No notion of time

Aargh… Those Pesky Side-Effects

let equal = sin(0.0) = sin(0.0)let sinzero = sin(0.0) in sinzero = sinzero

Binds name to value Equality != assignment

let equal = DateTime.Now = DateTime.Nowlet now = DateTime.Now in now = now

Not a pure function…

Immutability is the default

But We Like Side-Effects So Much…

// C# syntax

static void Main(string[] args){ Console.WriteLine(args.Length);}

(* F# syntax *)let main (args : string array) = printf "%d\n" args.Lengthval main : string array -> unit

In Haskell: IO unit

I/O is a side-effect

Philip Wadler

Hmm… monads

Programming in a Functional Style

FP

First class functions

Immutabledata

Referentialtransparency

Algebraic data types

Typeinference

Patternmatching

Essence

Niceties

But what’s a function?

F# – A General-Purpose Functional Style Language

Visual Studio

.NET

Functional

F#

DEMOFunctional Programming

Programming with Functions

An Exercise In Purity?$$

$$

Impure Pure

Purify yourselves, sinners!

Erik Meijer Simon Peyton-JonesWhere does

F# fit?

DYNAMIC PROGRAMMINGThe world isn’t always typed

Dynamic vs. Static

DynamicLanguages

Simple and succinct

Implicitly typed

Meta-programming

No compilation

StaticLanguages

Robust

Performant

Intelligent tools

Better scaling

REST

JavaScript

Ruby

JSON

Python

It’s a Dynamic World

• Trend on non-schematized data• Remember WSDL, SOAP, XSD?• How about REST, JSON?

• The next browser war• JavaScript on the web• Optimized scripting engines

• Towards metaprogramming?• Ruby community• Code as data

32-bit value 32-bit valueType tag

32-bit value

Type tag

32-bit value

Loop back to dispatcher

Fetch next byte codeCall generic add handler

Check for overflowStore type tag of result

Store value of result

Load type tag of aLoad type tag of i

Select add operationLoad value of aLoad value of i

Dynamic vs. Static

var a = 0;for (var i = 0; i < n; i++) { a = a + i;}

ADD instruction

10-100 X

int int

a i

Dynamic VM Advances

Interpretation

Interpretation

DynamicTyping

DynamicTyping

Operation

10-100 X

Interpreter

DynamicTyping

DynamicTyping

Operation

3-10 X

JIT Compiler

Operation

2-3 X

AdaptiveJIT Compiler

Inline CachingType Specialization

Hidden ClassesTracing

PythonBinder

RubyBinder

COMBinder

JavaScriptBinder

ObjectBinder

.NET Dynamic Programming

Dynamic Language Runtime

Expression Trees Dynamic Dispatch Call Site Caching

IronPython IronRuby C# VB.NET Others…

DEMODynamic Code and Data

Compiler as a Service

28

Class

Field

public Foo

private

string

X

CompilerCompilerSource codeSource code

SourceFile

Source codeSource code

.NET Assembly

Meta-programming Read-Eval-Print Loop

LanguageObject Model

DSL Embedding

CONCURRENT PROGRAMMINGDealing with hardware reality

Taming the Concurrency Monster

Can you keep the cores busy?

Gordon Moore

…can be hard

Concurrent programming with shared state…

Operating System Threads

Parallel Extensions in .NET 4

Parallel LINQ

Task Parallel Library Coordination Data Structures

CPU CPU …CPU CPU

Task-oriented

Data-oriented

Richcomposition

Coordinationand scheduling

TPL

Task<T> PLINQ

CDS, etc.Continuations

Task Parallel Library in .NET 4

Expressing Parallelism – A Library Approach

int[,] Multiply(int[,] m1, int[,] m2) { int m, n, o; // Left as an exercise var res = new int[m, o]; Parallel.For(0, m, i => { for (int j = 0; j < o; j++) { res[i, j] = 0; for (int k = 0; k < n; k++) { res[i, j] += m1[i, k] * m2[k, j]; } } }); return res;}

int[,] Multiply(int[,] m1, int[,] m2) { int m, n, o; // Left as an exercise var res = new int[m, o]; for (int i = 0; i < m; i++) { for (int j = 0; j < o; j++) { res[i, j] = 0; for (int k = 0; k < n; k++) { res[i, j] += m1[i, k] * m2[k, j]; } } } return res;}

Embarrassingly Parallel

Lambda expressions to the rescue

Expressing Parallelism – A Library Approach

var source = Enumerable.Range(1, 10000);var res = from x in source.AsParallel() where f(x) select g(x);

res.ForAll(x => { Process(x);});

var source = Enumerable.Range(1, 10000);var res = from x in source where f(x) select g(x);

foreach (var x in res) Process(x);

Natural Data Parallelism

Extension methods to the rescue

Asynchronous Programming – Low Hanging Fruit?

Your Program Here

Eventstriggered

I/O

completed

Packet

received

EventsCallbacks

Reactive

Asynchronous Programming Simplified

37

• Don’t block! UI programming, Windows Phone 7, Silverlight• Latency ahead! Dealing with networks, services, cloud

A blocking call!

var data = DownloadData(…);ProcessData(data);

Callback twists yourcode inside out

var data = DownloadDataAsync(…, data => { ProcessData(data);});

var data = await DownloadDataAsync(…);ProcessData(data);

No longer blocking!Visual Studio

Async CTP

DEMOUsing the TPL and the Async CTP

Potential Language Constructs

Immutability

Purity

Isolation

Exciting Times

45

• Horse-power of many-core…• …but how to program those?Concurrent

• Say what you want…• …not how it has to be done?Declarative

• Schematized, static, dynamic…• …so, what’s the sweet spot?Dynamic

• New level of expressiveness…• …how about the essence?Functional

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