Agus Kurniawan Microsoft MVP. Blog

Transcription

1 Agus Kurniawan Microsoft MVP Blog

2 Agenda Reasons The Paradigm The Technology The People Code Parallel Processing PLINQ Data and Synchronization Tools Debugging Profiling

3 Why? Because Single-Core Is Slow (Single-Threaded)

4 Power Density (W/cm 2 ) The Paradigm Hardware limitations due to heat increases Moore's Law implies more Cores not higher speeds 10,000 Sun s Surface 1,000 Rocket Nozzle 100 Nuclear Reactor Hot Plate 486 Pentium processors

5 GOPS The Shift More Cores More Parallel Computing 32,768 2, Parallelism Opportunity 80X

6 The Technology Intel (C) (software.intel.com)

7 The People "Everyone does it"

8 Writing Parallel Code is Hard (Multi-Threaded & Multi-Core)

9 Multi- Threaded Programming It's not easy Error Prone From Race conditions to data sharing Hard to Debug Very hard to reproduce Easy to break (on newer hardware) Dedication and perseverance Businesses want business value not hardcore developers writing threads

10 Simple Maths Demo 1, 2, 3, 5, 7, 11, 13, 17, 19, 23...

11 Calculating Prime Numbers List<int> primes = new List<int>(); for (int i = 2; i < upper; i++) { if (SieveOfEratosthenes.IsPrime(i)) primes.add(i); }

12 "My" Parallel int corecount = Environment.ProcessorCount; int partitionsize = upper / corecount; ManualResetEvent endevent = new ManualResetEvent(false); List<int> result = new List<int>(); object lockobject = new object(); int runninginstances = corecount; for (int i = 0; i < corecount; i++) { // partition per core ThreadPool.QueueUserWorkItem(c => { int core = (int)c; int partitionstart = core * partitionsize; int partitionend = ((core + 1) * partitionsize) - 1; for (int j = partitionstart; j < partitionend; j++) { if (SieveOfEratosthenes.IsPrime(j)) { lock (lockobject) { result.add(j); } } } if (Interlocked.Decrement(ref runninginstances) == 0) { endevent.set(); } }, i); } endevent.waitone(); Static Work Distribution Potential scalability bottleneck Error Prone Error Prone Manual locking Manual Synchronization

13 Parallel Prime Numbers var result = new ConcurrentBag<int>(); Parallel.For(2, upper, (x) => { if (SieveOfEratosthenes.IsPrime(x)) { result.add(x); } }); var result = new List<int>(); for (int i = 2; i < upper; i++) { if (SieveOfEratosthenes.IsPrime(i)) result.add(i); }

14 Ray tracer Boids

15 Architecture public static void Main(string[] args) {... } Declarative Parallel Queries Imperative Parallel Algorithms Compiler (F#, C#, VB...) PLINQ Execution Engine Task Parallel Library Parallel Constructs Task Scheduling Data Structures and Coordination Concurrent Collections Synchronization & Coordination T1 T2 T1 T2 CPU CPU

16 Library - Parallel Parallel.For & Parallel.ForEach Drop in replacement for for/foreach loop Core Partitioning Scalable Cancellable Parallel.Invoke Action Invoker Cancelation API Cooperative Cancellation

17 Coordination Structures Collections ConcurrentBag<T> ConcurrentStack<T> BlockingCollection Locks & Signals SpinLock & SpinWain SemaphoreSlim Barrier CountdownEvent

18 Blend Images

19 Library - Tasks Task & Task<T> Asynchronous Execution (Blocking) Value on competition Parent & Child Relationships Continuations on success, failure or cancellation Task Scheduler Scheduler on top of the ThreadPool Abstract implementation

20 Tasks Custom Scheduling Task Stealing Priority Scheduling Round Robin IO Scheduler

21 Fractals Putting Tasks to do some work

22 Library - PLINQ LINQ but Parallel IEnumerable<T>.AsParallel() Standard Operators Parallel Extensions Partitioning and Merging API Extensions.AsParallel() Direct Use: ParallelEnumerable.Select/Where...

23 PLINQ Partitioning: Range & Stride IList<T> Range Continuous ranges Stripped Round Robin, designed for Skip&Take

24 PLINQ Partitioning: Chunk & Hash IEnumerable<T> Chunk Single Enumerator (locked), chunks of increasing size handled Hash Used for Join, GroupJoin, GroupBy, Distinct, Except, Union and Intersect

25 PLINQ Ray Tracer

26 Task Debugging Parallel Tasks All scheduled tasks All running tasks Parallel Stacks Call graphs Call stacks

27 Parallel + MS Excel 2010

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29 Resources Sessions On-Demand & Community Microsoft Certification & Training Resources Resources for IT Professionals Resources for Developers

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