ParallelFx, bringing Mono applications in the multicore era

multicore computer are now part of our everyday life. Most desktop and laptop machines out there bundle a dual-core processor, quad-core processor or even 8-core processor by default. This multiplication of the number of core on the same chip is destined to become the way for manufacturers to remain competitive. However, developers were a bit left out in this process, having written sequential programs for ages whereas they were now required to parallelize their program to make them efficient which isn't an easy step to take.\r\n\r\nThat's why we now see the apparition of framework designed to help programmers to take advantage of this new architecture of processor by hiding away the parallel difficulty under primitives that they are used to. ParallelFx is one of such framework for the Mono and .NET world. By providing several new parallel constructs and concurrent data structures, it allows Mono applications to enter painlessly in this new multicore era.

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1. ParallelFx Bringing Mono applications in the multicore era Jérémie Laval @ jeremie.laval@gmail.com http://blog.neteril.org http://twitter.com/jeremie_laval IRC Garuma on #mono @ GIMPNet.org
2. Outline Why bother? The free lunch An awesome idea Remaining performant ParallelFx The big picture Tasks and co PLinq State of things A note for the future
3. Why bother? ParallelFx A note for the future Questions Why are we bothering with parallelization 3 / 23
4. Why bother? ParallelFx A note for the future Questions Why are we bothering with parallelization Everyone loves his single thread 3 / 23
5. Why bother? ParallelFx A note for the future Questions Why are we bothering with parallelization Everyone loves his single thread “The ideal number of thread you should use is 1” – Alan Mc Govern Mono hacker 3 / 23
6. Why bother? ParallelFx A note for the future Questions Why are we bothering with parallelization Everyone loves his single thread – Alan Mc Govern Mono hacker 3 / 23
7. Why bother? ParallelFx A note for the future Questions Why are we bothering with parallelization 4 / 23
8. Why bother? ParallelFx A note for the future Questions Why are we bothering with parallelization Because the free lunch is over! 4 / 23
9. Why bother? ParallelFx A note for the future Questions Free lunch? 70’s - 2005: Moore’s law in action Intel Processor Clock Speed (MHz) 10000 1000 100 10 1 0.1 1968 1973 1979 1984 1990 1995 2001 2006 8080 80286 80386 80486 Pentium Celeron Pentium III Pentium 4 (Prescott) Core 2 Extreme Multicore crisis is here ! Source: Smoothspan blog 5 / 23
10. Why bother? ParallelFx A note for the future Questions The awesome idea 6 / 23
11. Why bother? ParallelFx A note for the future Questions The awesome idea Can’t scale vertically? Scale horizontally! 6 / 23
12. Why bother? ParallelFx A note for the future Questions Trend of things Number of cores 1 2 4 12ish 80 Pentium Core Duo Core 2 Quad Core i7-980X Intel prototype 7 / 23
13. Why bother? ParallelFx A note for the future Questions Problem 8 / 23
14. Why bother? ParallelFx A note for the future Questions Problem No more magical free-lunch 8 / 23
15. Why bother? ParallelFx A note for the future Questions Solution Let’s break up work... ....and share it among cores 9 / 23
16. Why bother? ParallelFx A note for the future Questions Errr... 10 / 23
17. Why bother? ParallelFx A note for the future Questions Parallelization is difficult 11 / 23
18. Why bother? ParallelFx A note for the future Questions Parallelization is difficult Hard: is that stuff really thread safe? 11 / 23
19. Why bother? ParallelFx A note for the future Questions Parallelization is difficult Hard: is that stuff really thread safe? Tedious: whose turn is it to debug deadlocks? 11 / 23
20. Why bother? ParallelFx A note for the future Questions Parallelization is difficult Hard: is that stuff really thread safe? Tedious: whose turn is it to debug deadlocks? Inefficient: how many thread to use? 11 / 23
21. Why bother? ParallelFx A note for the future Questions Parallelization is difficult Hard: is that stuff really thread safe? Tedious: whose turn is it to debug deadlocks? Inefficient: how many thread to use? Too few: it’s not scaling 11 / 23
22. Why bother? ParallelFx A note for the future Questions Parallelization is difficult Hard: is that stuff really thread safe? Tedious: whose turn is it to debug deadlocks? Inefficient: how many thread to use? Too few: it’s not scaling Too much: context-switching hurts performance 11 / 23
23. Why bother? ParallelFx A note for the future Questions Parallelization is difficult Hard: is that stuff really thread safe? Tedious: whose turn is it to debug deadlocks? Inefficient: how many thread to use? Too few: it’s not scaling Too much: context-switching hurts performance What if the number of core changes? 11 / 23
24. Why bother? ParallelFx A note for the future Questions KISS time (Keep it simple, stupid) We need something different : 12 / 23
25. Why bother? ParallelFx A note for the future Questions KISS time (Keep it simple, stupid) We need something different : Automagically regulate thread usage at runtime 12 / 23
26. Why bother? ParallelFx A note for the future Questions KISS time (Keep it simple, stupid) We need something different : Automagically regulate thread usage at runtime As straightforward as possible 12 / 23
27. Why bother? ParallelFx A note for the future Questions KISS time (Keep it simple, stupid) We need something different : Automagically regulate thread usage at runtime As straightforward as possible Simulate familiar constructs 12 / 23
28. Why bother? ParallelFx A note for the future Questions KISS time (Keep it simple, stupid) We need something different : Automagically regulate thread usage at runtime As straightforward as possible Simulate familiar constructs Reuse existing code with only slight modification 12 / 23
29. Why bother? ParallelFx A note for the future Questions Enter ParallelFx ParallelFx at a glance 13 / 23
30. Why bother? ParallelFx A note for the future Questions At the heart Work-stealing scheduler Mono Application Shared work pool ParallelFX library (Scheduler) Thread Worker Local work pool OS thread Thread Worker Local work pool OS thread Steal Retrieve Manage 14 / 23
31. Why bother? ParallelFx A note for the future Questions Tasks CancellationTokenSource source = new CancellationTokenSource (); Task task = Task.Factory.StartNew (() => DoSomeStuff (), source.Token); Task continuation = task.ContinueWith ((t) => Console.WriteLine ("task finished"); source.Cancel (); t.Wait (); 15 / 23
32. Why bother? ParallelFx A note for the future Questions Future (Task<T>) static int SumParallel (Tree<int> tree, int curDepth) { const int SequentialThreshold = 3; if (tree == null) return 0; if (curDepth > SequentialThreshold) return SumSequentialInternal (tree); int right = SumParallel (tree.Right, curDepth + 1); Task<int> left = Task.Factory.StartNew (() => SumParallel (tree.Left, curDepth + 1)); return tree.Data + left.Value + right; } 16 / 23
33. Why bother? ParallelFx A note for the future Questions Parallel.For Fractal fractal = new Fractal (width, height); ColorChooser colorChooser = new ColorChooser (); Parallel.For (0, width, (i) => { for (int j = 0; j < height; j++) { ProcessPixel (i, j, fractal, colorChooser); } }); 17 / 23
34. Why bother? ParallelFx A note for the future Questions Demo: Parallel For Demo: image processing with parallel loops 18 / 23
35. Why bother? ParallelFx A note for the future Questions PLinq ParallelEnumerable.Range (1, 1000)./* ... */ ParallelEnumerable.Repeat (‘‘Rupert’’, 1000)./* ... */ enumerable.AsParallel ()./* ... */ var query = from x in Directory.GetFiles ("/etc/") .AsParallel () where x.EndsWith (".conf") select x; query.ForAll ((e) => { Console.WriteLine ("{0} from {1}", e, Thread.CurrentThread.ManagedThreadId); }); 19 / 23
36. Why bother? ParallelFx A note for the future Questions Demo: PLinq Demo: raytracing the PLinq way 20 / 23
37. Why bother? ParallelFx A note for the future Questions State of things Mono 2.6 (December 2009): .NET 4 beta 1 Task, Future, Parallel loops Concurrent collections Coordination data structures Mono 2.8 (or git master): .NET 4 compliant Enabled by default Tons of improvement With PLinq! 21 / 23
38. Why bother? ParallelFx A note for the future Questions A note for the future 22 / 23
39. Why bother? ParallelFx A note for the future Questions A note for the future GLinq: GPGPU-powered Linq 22 / 23
40. Why bother? ParallelFx A note for the future Questions A note for the future GLinq: GPGPU-powered Linq Re-use PLinq pipeline 22 / 23
41. Why bother? ParallelFx A note for the future Questions A note for the future GLinq: GPGPU-powered Linq Re-use PLinq pipeline Same design guidelines than PLinq: simplicity, transparency 22 / 23
42. Why bother? ParallelFx A note for the future Questions A note for the future GLinq: GPGPU-powered Linq Re-use PLinq pipeline Same design guidelines than PLinq: simplicity, transparency Rewrite C# code in OpenCL (Expression trees FTW!) 22 / 23
43. Why bother? ParallelFx A note for the future Questions A note for the future GLinq: GPGPU-powered Linq Re-use PLinq pipeline Same design guidelines than PLinq: simplicity, transparency Rewrite C# code in OpenCL (Expression trees FTW!) Transparent mapping of OpenCL idioms to .NET 22 / 23
44. Why bother? ParallelFx A note for the future Questions Closing the curtains 23 / 23