多核错误共享

以下程序中是否会发生错误共享?

记忆

• 1个数组分为4个相等的区域: [A1, A2, B1, B2]
• 每个区域填充为64字节的倍数。

步骤

1. thread 1 write to region A1 and A2 while thread 2 write to region B1 and B2.
2. barrier
3. thread 1 read B1 and write to A1 while thread 2 read B2 and write to A2.
4. barrier
5. Go to step 1.

#include <vector>
#include <iostream>
#include <stdint.h>
int main() {
    int N = 64;
    std::vector<std::int32_t> x(N, 0);
    #pragma omp parallel
    {
        for (int i = 0; i < 1000; ++i) {
            #pragma omp for
            for (int j = 0; j < 2; ++j) {
                for (int k = 0; k < (N / 2); ++k) {
                    x[j*N/2 + k] += 1;
                }
            }
            #pragma omp for
            for (int j = 0; j < 2; ++j) {
                for (int k = 0; k < (N/4); ++k) {
                    x[j*N/4 + k] += x[N/2 + j*N/4 + k] - 1;
                }
            }
        }
    }
    for (auto i : x ) std::cout << i << " ";
    std::cout << "\n";
}

结果

32 elements of 500500 (1000 * 1001 / 2)
32 elements of 1000