Beautiful code #7 - std::thread, std::accumulate 👋

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#include <iostream>
#include <vector>
#include <thread>
#include <numeric>

// Function to calculate the sum of a portion of the array
int sumPartialArray(const std::vector<int>& array, int start, int end) {
    return std::accumulate(array.begin() + start, array.begin() + end, 0);
}

int main() {
    const int numThreads = 4;  // Number of threads to use
    const int arraySize = 1000000;  // Size of the array

    // Create and initialize the array
    std::vector<int> array(arraySize);
    for (int i = 0; i < arraySize; ++i) {
        array[i] = i + 1;
    }

    // Create a vector of threads
    std::vector<std::thread> threads(numThreads);

    // Calculate the sum using multiple threads
    int blockSize = arraySize / numThreads;
    int start = 0;
    int end = blockSize;

    std::vector<int> partialSums(numThreads);  // Vector to store partial sums

    for (int i = 0; i < numThreads; ++i) {
        // Launch a thread to calculate the sum of a portion of the array
        threads[i] = std::thread([&array, start, end, i, &partialSums]() {
            partialSums[i] = sumPartialArray(array, start, end);
        });

        // Update the start and end indices for the next thread
        start = end;
        end += blockSize;
    }

    // Wait for all the threads to finish
    for (auto& thread : threads) {
        thread.join();
    }

    // Combine the partial sums calculated by each thread
    int totalSum = std::accumulate(partialSums.begin(), partialSums.end(), 0);

    std::cout << "Total sum: " << totalSum << std::endl;

    return 0;
}