使用 openMP v. 2.0 并行化过滤器迭代器

Question

我有一个大向量。我想同时增加正成员。

class is_positive_number {
public:
    bool operator()(int x) { return 0 < x; }
};

int main()
{
    int numbers_[] = { 0, -1, 4, -3, 5, 8, -2, 3, 4, -1 };
    const int N = sizeof(numbers_) / sizeof(int);   
    std::vector<int> test_vec(numbers_, numbers_ + N);

    std::cout << "max: " << omp_get_max_threads() << std::endl;
    int number_of_threads = 4;
    int SubVecLen = N / number_of_threads,
        LeftOvers = N % number_of_threads;
    int k = 0, i = 0, n = 0;
    std::vector<int> start_vec, end_vec;
    while (n < number_of_threads)
    {
        k += i;
        i = (SubVecLen + (LeftOvers-- > 0 ? 1 : 0));
        start_vec.push_back(k);
        end_vec.push_back((k + i - 1));

        ++n;
    }
    for (size_t n = 0; n < number_of_threads; n++)
    {
        std::cout << start_vec[n] << "\t" << end_vec[n] << "\n";
    }

    is_positive_number predicate;
    typedef boost::filter_iterator<is_positive_number, std::vector<int>::iterator>
        FilterIter;

#pragma omp parallel
    {
#pragma omp for
        for (int s = 0; s < 4; s++)
        {
            FilterIter filter_iter_first(predicate, test_vec.begin(), (test_vec.begin() + start_vec[omp_get_thread_num()]) );
            FilterIter filter_iter_last(predicate, test_vec.begin(), (test_vec.begin() + end_vec[omp_get_thread_num()] + 1) );

            for (auto iter = filter_iter_first;
                iter != filter_iter_last; iter++)
            {
                std::cout << "num: " << *iter << std::endl;
                (*iter) = (*iter) + 1;
            }

        }
    }

    for (size_t n = 0; n < test_vec.size(); n++)
    {
        std::cout << test_vec[n] << "\n";
    }
    return 0;
}

结果错误！

然而，我要解决的实际问题比这个更复杂。我试图简化我的问题，以便更容易理解。我还必须提到，我只能使用 openMP v.2.0。这就是为什么我尝试拆分向量并将向量的每个部分专用于特定线程的原因。

如有任何想法，我们将不胜感激。

Answer 1

您在创建过滤器迭代器时使用了错误的开始和停止索引。我附上了一个工作示例。我用 s 到 select 并行 for 语句中的线程。不确定你的版本是否也适用，所以我将其更改为我习惯的版本。

#pragma omp parallel
{
    #pragma omp for
    for (int s = 0; s < 4; s++)
    {
        /* The following lines are important */
        FilterIter filter_iter_first(predicate, test_vec.begin() + start_vec[s], (test_vec.begin() + end_vec[s] + 1));
        FilterIter filter_iter_last(predicate, test_vec.begin() + end_vec[s] + 1, (test_vec.begin() + end_vec[s] + 1));

        for (auto iter = filter_iter_first; iter != filter_iter_last; iter++)
        {
            std::cout << "num: " << *iter << std::endl;
            (*iter) = (*iter) + 1;
        }
    }
}

使用 openMP v. 2.0 并行化过滤器迭代器

parallelize filter iterator using openMP v. 2.0

c++

openmp

boost-iterators