partial-reduction.c

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>

using namespace std;
const int M = 10;
const int N = 64;
float simple(float A[][N], int m, int n) {
    float sum = 0;
    for (int i = 0; i < m; i++)
        for (int j = 0; j < n; j++)
            sum += A[i][j];
    return sum;
}

float psum(float A[][N], int m, int n) {
    float psum[M] = {0};

    for (int i = 0; i < m; i++)
        for (int j = 0; j < n; j++)
            psum[i] += A[i][j];
    
    float sum = 0;
    for (int i = 0; i < m; i++)
        sum += psum[i];
    return sum;
}

int main() {
    float A[M][N];
    for (int i = 0; i < M; i++)
        for (int j = 0; j < N; j++)
            A[i][j] = 0.1;
    
    std::cout.precision(std::numeric_limits<float>::max_digits10);
    cout << simple(A, M, N) << "\n";
    cout << psum(A, M, N) << "\n";
}