OpenMP And C++
- 1. OpenMP and C++ Sb î rlea Drago ș
- 2. Summary Why use C++ and OpenMP Why are there problems Objects in OpenMP clauses Parallelization of C++ loops STL Iterator loop problems STL Dataypes problems
- 3. 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
- 4. Why are there problems? The OpenMP specification includes C++ Compiler implementations do offer consistent behaviour OpenMP standard too restrictive for C++ syntax parallelization
- 5. Objects in OpenMP clauses
- 6. Objects in OpenMP clauses Shared = All threads access the same storage area for each shared object C all to dummyfunc expected
- 7. Objects in OpenMP clauses 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
- 8. Objects in OpenMP clauses 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
- 9. Objects in OpenMP clauses 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
- 10. Parallelization of C++ loops OpenMP Requirement: “signed integer variable” as loop index Size_t loop index stops parallelization STL iterators stop parallelization
- 13. High Level code Parallelization Options: Internal parallelization Mixed parallelization
- 14. STL datatypes std:vallarray Guaranteed 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
- 15. Reference OpenMP and C++ By Christian Terboven and Dieter an Mey