High-level%20Multithreaded%20Programming%20[Part%20III]

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High-level Multithreaded Programming Part III

• Primož Gabrijelcic

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Background Information
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About Me

• Primož Gabrijelcic
• Programmer, consultant, writer, speaker
• thedelphigeek.com
• www.glagolite.si/delphi
• Hacking multithreaded code since 1999

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About OmniThreadLibrary

• VCL for multithreading
• Delphi 2007 XE34
• Open source OpenBSD license
• www.omnithreadlibrary.com
• omnithreadlibrary.googlecode.com
• Win32/Win64

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About the Webinars

• Code and video www.omnithreadlibrary.com/webinars
  
• Code free, video 10
• 20 free books, courtesy of the De Novo Software,
  www.denovosoftware.com

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High-Level Abstractions

• ParallelTask
• BackgroundWorker
• Pipeline
• ForkJoin

• Async /Await
• Future
• Join
• ForEach

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Which abstraction to use?

• Consider data flow!

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High-Level Abstractions

• ParallelTask
• BackgroundWorker
• ForkJoin
• Pipeline

• Async /Await
• Future
• Join
• ForEach

Parallel iteration over data
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ForEach
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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

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Special features

• Synchronized access to data
• Data prefetching
• Work stealing
• Optional output ordering
• Aggregation

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Aggregation

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

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Demos

• 35_ParallelFor
• 36_ParallelAggregate
• 38_OrderedFor

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High-Level Abstractions

• ParallelTask
• BackgroundWorker
• ForkJoin
• Pipeline

• Async /Await
• Future
• Join
• ForEach

Parallelization of multistage operations
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Pipeline
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Example
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Web Spider
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Parting Notes
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Keep in Mind

• Dont parallelize everything
• Rethink the algorithm
• Data flow dictates the abstraction
• Measure the improvements
• Test, test and test

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Code

• Will be available shortly at
• www.omnithreadlibrary.com/webinars