For_Each and Reduce Algorithms
This lesson goes into the details of reduce algorithm and its working.
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for_each Algorithm
In the serial version of for_each, the version that was available before C++17 you get a unary function as a return value from the algorithm.
Returning such an object is not possible in a parallel version, as the order of invocations is indeterminate.
Here’s a basic example:
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void ForEachTest() {std::vector<int> v(100);std::iota(v.begin(), v.end(), 0);std::for_each(std::execution::par, v.begin(), v.end(),[](int& i) { i += 10; });std::for_each_n(std::execution::par, v.begin(), v.size() / 2,[](int& i) { i += 10; });}int main() {ForEachTest();return 0;}
The first for_each algorithm will update all of the elements of a vector, while the second execution will work only on the first half of the container.