parallel reduction

// 归约操作是OpenMP编程方式给同步编程带来的特殊的编程功能，该操作// 会反复将一个二元运算符应用在一个变量和另一个值上，并把结果保存// 在原变量中，通过reduction语句提供            double zz = 0.0, Sum = 0.0;            omp_set_num_threads(2);#pragma omp parallel for reduction(+:Sum) private(zz)            for(int i = 0; i < 1000; i++)            {                zz = 2 * i;                Sum += zz;            }            cout << Sum << endl;// 另一个例子int i, n, chunk;            float a[100], b[100], result;            n = 100;            chunk = 10;            result = 0.0;            for(i = 0; i < n; i++)            {                a[i] = i * 1.0;                b[i] = i * 2.0;            }#pragma omp parallel for reduction(+:result)            for(i = 0; i < n; i++)                result = result + a[i] * b[i];            cout << result << endl;