omp 并行运算，float计算误差那么大，怎么办_(语言-c++)

Question

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// 开启omp并行, float计算误差累积到了0.2.
{
    std::cout.precision(14);

    std::array<float, 100000> da;
    for (size_t i = 0; i < da.size(); i++)
        da[i] = 1.0f * i / da.size();

    long cnt = 0;
    float cf = 0;
    double cdb = 0;
#pragma omp parallel for         
    for (int i = 0; i < 100000; i++)
    {
#pragma omp critical
        {
            cnt++;
            cf += da[i];
            cdb += da[i];
        }
    }
    // x86 debug 输出: 100000    49999.6953125    49999.5    (49999.6953125这个值, 还每次都不一样)
    // x86 release 输出: 100000    49999.54296875    49999.5    (49999.54296875这个值, 还每次同样不一样)
    std::cout << cnt << " " << cf << " " << cdb << std::endl;	

    cnt = 0;
    cf = 0;
    cdb = 0;
    for (int i = 0; i < 100000; i++)
    {
        cnt++;
        cf += da[i];
        cdb += da[i];
    }

    // x86 debug 输出: 100000    49999.51171875    49999.5
    // x86 release 输出: 100000    49999.51171875    49999.5
    std::cout << cnt << " " << cf << " " << cdb << std::endl;
}

Answer 1

float误差打球，你用用精度更高的double