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H IGH - LEVEL M ULTITHREADED P ROGRAMMING [P ART III] Primož Gabrijelčič.

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Presentation on theme: "H IGH - LEVEL M ULTITHREADED P ROGRAMMING [P ART III] Primož Gabrijelčič."— Presentation transcript:

1 H IGH - LEVEL M ULTITHREADED P ROGRAMMING [P ART III] Primož Gabrijelčič

2 B ACKGROUND I NFORMATION

3 About Me Primož Gabrijelčič Programmer, consultant, writer, speaker – thedelphigeek.com – Hacking multithreaded code since 1999

4 About OmniThreadLibrary „VCL for multithreading“ Delphi 2007 – XE3[4] Open source – OpenBSD license – – omnithreadlibrary.googlecode.com Win32/Win64

5 About the Webinars Code and video: Code = free, video = $10 20 free books, courtesy of the De Novo Software,

6 High-Level Abstractions Async [/Await] Future Join ForEach ParallelTask BackgroundWorker Pipeline ForkJoin

7 Which abstraction to use? Consider data flow!

8 High-Level Abstractions Async [/Await] Future Join ForEach ParallelTask BackgroundWorker ForkJoin Pipeline Parallel iteration over data

9 ForEach

10 Iterate over … Integer range Enumerable collection (TStringList …) Thread-safe enumerable collection (OTL) Blocking collection (IOmniBlockingCollection) Anything – Custom enumerator function – Main program writing into a blocking collection

11 Special features Synchronized access to data Data prefetching Work stealing Optional output ordering Aggregation

12 aggregate := initial value for each value in source Execute(value, result) if not result.IsEmpty then Agreggator(aggregate, value)

13 Demos 35_ParallelFor 36_ParallelAggregate 38_OrderedFor

14 High-Level Abstractions Async [/Await] Future Join ForEach ParallelTask BackgroundWorker ForkJoin Pipeline Parallelization of multistage operations

15 Pipeline

16 Example

17 Web Spider

18 P ARTING N OTES

19 Keep in Mind Don’t parallelize everything Rethink the algorithm Data flow dictates the abstraction Measure the improvements Test, test and test

20 Code Will be available shortly at


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