Multiple Return Values in Cilk

In Cilk, we can demonstrate multiple return values using a structure. Here’s an example that shows how to return and use multiple values:

#include <cilk/cilk.h>
#include <iostream>
#include <utility>

// We use a std::pair to return two integers
std::pair<int, int> vals() {
    return std::make_pair(3, 7);
}

int main() {
    // Here we use structured binding (C++17 feature) to assign the returned values
    auto [a, b] = vals();
    std::cout << a << std::endl;
    std::cout << b << std::endl;

    // If you only want a subset of the returned values,
    // you can use std::tie with std::ignore
    int c;
    std::tie(std::ignore, c) = vals();
    std::cout << c << std::endl;

    return 0;
}

In this Cilk example, we’re using C++ features to mimic multiple return values:

1. The vals() function returns a std::pair<int, int>, which allows us to return two integers.

2. In the main() function, we use structured binding (a C++17 feature) to easily assign the returned values to a and b.

3. To demonstrate ignoring one of the returned values, we use std::tie with std::ignore. This is similar to using the blank identifier _ in other languages.

To compile and run this Cilk program:

$ g++ -fcilkplus multiple-return-values.cpp -o multiple-return-values
$ ./multiple-return-values
3
7
7

While Cilk doesn’t have built-in support for multiple return values like some other languages, we can achieve similar functionality using C++ features such as std::pair, structured bindings, and std::tie.

This approach allows us to return and use multiple values from a function in a clean and efficient manner, which is particularly useful when a function needs to return both a result and an error status, or when multiple related values need to be returned together.