CODEWITHSUNDEEP
c++openmpvalarray
001001
001001

Reputation: 588

How to efficiently slice c++ vector with omp?

I am having a hard time understanding the relationship between omp parallel and vector slicing within each thread.

I was trying with std::vector but switched to std:valarray to try and minimize the slice copying, although I assume it is not relevant here.

For example, there is a vector:

std::valarray<custType> myvec(dataset.size());

I have some efficient functions that take a vector as input and do some computation, so I want to maximize the chunk size and pass the sliced valarray.

The general idea is:

    std::valarray<custType> myvec(dataset.size());
#pragma omp parallel for schedule(static)
    for (int i = 0; i < dataset.size(); i++) {
        // Get the start and end index of this chunk
        std::slice indexSlice(thread_start to thread_end);
        // Assign the orginal datasets values to the newly calculated ones
        dataset[indexSlice] = vectorizedFunction(myvec[indexSlice]);
    }

When using omp parallel for, I don't understand how to get all indices at once so that I can slice the vector to send to a function (as shown in the indexSlice being thread_start to thread_end).

The other approach/idea was to make my own chunk definitions of (start,end) indices, then parallelize the for loop over those chunks, but this seems like a weird solution when there is a parallelization library already. Is there an easier/cleaner/better way to do it (like how I am trying above), or is making a set of chunk indices the right way?

Upvotes: 1

Views: 156

Answers (0)

Related Questions