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Parallelizaton for stdlist problem

  1. Mar 14, 2013 #1
    Hi all,
    I am trying to using OpenMP to parallelize a loop in C++.
    The iterator for the loop is defined by std::list using C++ standard library containers.
    The following is an example:


    for (std::list<int>::iterator it=mylist.begin() ; it != mylist.end(); ++it)
    std::cout << ' ' << *it;

    However, I found I can not use OpenMP command to do the parallelzation (#pragma). The simulation runs very slowly. For OpenMP, the first index in the for loop must be a integer for parallelzation. Does anyone encounter the same problem and have any idea how to solve it? Thank you very much!
     
  2. jcsd
  3. Mar 14, 2013 #2

    mfb

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    2016 Award

    Staff: Mentor

    You want to parallelize "cout"s? I don't see how this is supposed to work.
     
  4. Mar 14, 2013 #3

    AlephZero

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    Science Advisor
    Homework Helper

    The basic idea of a "list" is that the entries are linked in sequence, by pointers.

    All the "nice" C++ syntax like iterators, the ++ operator, etc isn't "magic". All it does is hide the details from you (which is useful, because you don't have to change the code if you replace the list by a diferent data structure).

    The only way to parallelize access to the list entries would be to split it into several sub-lists.
     
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