openMP wordcount

OpenMP (Open Multi-Processing) is a set of programming interfaces used for parallel computing. It supports multi-platform shared memory multiprocessing programming in C, C++, and Fortran.

To implement wordcount using OpenMP, we can use the following steps:

1. Read in the input text file.
2. Split the input text file into chunks of equal size.
3. Assign each chunk to a thread.
4. Count the words in each chunk using a local word count variable.
5. Merge the local word counts into a global word count variable.
6. Print the total word count.

Here's an example implementation of wordcount using OpenMP in C++:

#include <iostream>
#include <fstream>
#include <omp.h>

int main(int argc, char* argv[]) {
    // Read input file
    std::ifstream inputFile(argv[1]);
    if (!inputFile) {
        std::cerr << "Error: Could not open input file" << std::endl;
        return 1;
    }

    // Get file size
    inputFile.seekg(0, std::ios::end);
    const size_t fileSize = inputFile.tellg();
    inputFile.seekg(0, std::ios::beg);

    // Split input file into chunks
    const size_t numThreads = omp_get_max_threads();
    const size_t chunkSize = fileSize / numThreads;
    std::vector<char> inputBuffer(fileSize);
    inputFile.read(inputBuffer.data(), fileSize);
    std::vector<char*> chunkStarts(numThreads);
    std::vector<size_t> chunkSizes(numThreads);
    for (size_t i = 0; i < numThreads; ++i) {
        chunkStarts[i] = inputBuffer.data() + i * chunkSize;
        chunkSizes[i] = (i == numThreads - 1) ? fileSize - i * chunkSize : chunkSize;
    }

    // Count words in each chunk
    size_t totalWordCount = 0;
    #pragma omp parallel for reduction(+:totalWordCount)
    for (size_t i = 0; i < numThreads; ++i) {
        char* chunkStart = chunkStarts[i];
        size_t chunkSize = chunkSizes[i];
        size_t localWordCount = 0;
        for (size_t j = 0; j < chunkSize; ++j) {
            if (std::isspace(chunkStart[j]) && !std::isspace(chunkStart[j - 1])) {
                ++localWordCount;
            }
        }
        totalWordCount += localWordCount;
    }

    // Print total word count
    std::cout << "Total word count: " << totalWordCount << std::endl;

    return 0;
}

In this implementation, we first read in the input file and split it into chunks. We then use OpenMP to assign each chunk to a thread and count the words in each chunk. Finally, we merge the local word counts into a global word count variable and print the total word count.