This document discusses parallel programming in .NET 4.0. It notes that processor speeds have stopped increasing significantly and cores are increasing instead. It introduces parallel programming concepts in .NET 4.0 like PLINQ for declarative data parallelism, Parallel.For for imperative data parallelism, and tasks for splitting computations. It also discusses concurrent collections and provides examples of using PLINQ, Parallel.For, tasks, and continuations for parallel programming.

1. .Net 4.0 Threading
& Parallel Programming
Alex Moore
Consultant, HMB Inc.

2. No More Free Lunch
Processors not getting much faster

3. No More Free Lunch
transistors++

4. No More Free Lunch
transistors++ speed++

5. No More Free Lunch
transistors++ speed++

6. No More Free Lunch
transistors++ speed++
cores++

7. Elephant in the Room

8. Elephant in the Room
Parallel / Concurrent Programming is
reaching its boiling point

9. Elephant in the Room
Can’t ignore it any longer

10. New in .Net 4.0
D PLINQ
S
C Task Parallel Library
System.Threading

11. How to Express
Parallelism

12. How to Express
Parallelism
Threading sucks.

13. How to Express
Parallelism
Declarative data parallelism - PLINQ

14. How to Express
Parallelism
Declarative data parallelism - PLINQ
Imperative data parallelism - Parallel.For

15. How to Express
Parallelism
Declarative data parallelism - PLINQ
Imperative data parallelism - Parallel.For
Imperative task parallelism - Tasks

16. PLINQ
PLINQ provides us with ways to
declaratively partition and merge
our data.

17. PLINQ
from x in set
where x == somevalue
select expensiveFunction(x);

18. PLINQ
from x in set
where x == somevalue
select expensiveFunction(x);
from x in set.AsParallel()
where x == somevalue
select expensiveFunction(x);

19. For && ForEach
Task Parallel Library provides us
automatically parallelizing
versions of For and ForEach.

20. Parallel.For
for( int i = 0; i < 10; i++ )
{ ... }

21. Parallel.For
for( int i = 0; i < 10; i++ )
{ ... }
Parallel.For( 0, 10, i =>
{ ... } );

22. Parallel.ForEach
foreach( var x in set ) { ... }

23. Parallel.ForEach
foreach( var x in set ) { ... }
Parallel.ForEach( set, x => {...});

24. Tasks
Tasks allow us to split our
computations into blocks or “tasks”
that can be handled independently.

25. Tasks
A();
B();
C();
Do_Something();

26. Tasks
Task t1 = Task.Factory.StartNew(
()=> A(); );
Task t2 = Task.Factory.StartNew(
()=> B(); );
Task t3 = Task.Factory.StartNew(
()=> C(); );
Task.WaitAll(t1, t2, t3);
Do_Something();

27. Task<T>
string a = A();
int b = B();
double c = C();
Do_Something(a,b,c);

28. Task<T>
Task<string> a =
Task<string>.Factory.StartNew( ()=> A(); );
Task<int> b =
Task<int>.Factory.StartNew( ()=> B(); );
Task<double> c =
Task<double>.Factory.StartNew( ()=> C(); );
Do_Something(a.Result,b.Result,c.Result);

29. Continuations
String s = A();
Console.WriteLine(s);

30. Continuations
var t = new Task<string>(
()=> A() );
t.ContinueWith( s =>
Console.WriteLine(s) );
t.Start;

31. Concurrent Collections
• Threadsafe collections
• Use lightweight locking

32. Concurrent Collections
• BlockingCollection<T>
• ConcurrentBag<T>
• ConcurrentDictionary<T>
• ConcurrentQueue<T>
• ConcurrentStack<T>

33. Demos

34. Box of Sharp Knives

35. Box of Sharp Knives
★ Not a silver bullet for performance

36. Box of Sharp Knives
★ Not a silver bullet for performance
✓ Read, Do, and Learn

37. Questions?
Comments ?

38. How to find info
• http://msdn.microsoft.com/en-us/library/
dd460693.aspx
• http://code.msdn.microsoft.com/ParExtSamples
• Concurrent Programming on Windows
- Joe Duffy
• Patterns of Parallel Programming
- Stephen Toub

39. Thanks!
moore.alex@gmail.com
@alexmoore
www.enginerding.com