OpenMP And C++

OpenMP And C++

• 1.
  OpenMP and C++Sb î rlea Drago ș
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  Summary Why useC++ and OpenMP Why are there problems Objects in OpenMP clauses Parallelization of C++ loops STL Iterator loop problems STL Dataypes problems
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  Why use C++and OpenMP? OpenMP = fast implementation for parallel programs C++ = fast and mentenable implementation for large programs Both are useful when TTM is important
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  Why are thereproblems? The OpenMP specification includes C++ Compiler implementations do offer consistent behaviour OpenMP standard too restrictive for C++ syntax parallelization
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  Objects in OpenMPclauses
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  Objects in OpenMPclauses Shared = All threads access the same storage area for each shared object C all to dummyfunc expected
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  Objects in OpenMPclauses Private = Each thread should have its own instance of a variable. A new list item of the same type, with automatic storage duration, is allocated. Calls to constructor, dummyfunc , destructor expected
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  Objects in OpenMPclauses Firstprivate = Each thread should have its own instance of a variable, and the variable should be initialized with the value of the variable before the parallel construct. Copy constructor, dummyfunc, destructor calls expected
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  Objects in OpenMPclauses Lastprivate = the enclosing context's version of the variable is set equal to the private version of whichever thread executes the final iteration (for-loop construct) or last section (#pragma sections). Assignment operator call expected
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  Parallelization of C++loops OpenMP Requirement: “signed integer variable” as loop index Size_t loop index stops parallelization STL iterators stop parallelization
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  STL Iterator problem
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  STL Iterator problem
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  High Level codeParallelization Options: Internal parallelization Mixed parallelization
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  STL datatypes std:vallarrayGuaranteed initialization with 0 All data in memory of one processor (ccNUMA disadvantage) Solutions: STL modification => compiler dependent Custom allocator (std:vector) Solaris page migration=>Solaris dependent
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  Reference OpenMP andC++ By Christian Terboven and Dieter an Mey
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  Questions? Thank You!