std::async doesn't parallelize tasks
c++, c++11, gcc
Solution
You might need to add a launch policy of `std::launch::async`:
std::async(std::launch::async, foo);
Problem
Using C++11 std::async in this snippet: ``` int foo() { ::sleep(2); return 123; } int main() { future<int> r1(async(foo)); int r2 = foo(); cout << r1.get() + r2 << endl; return 0; } ``` It produces the right result, but runs both foo's serially (whole app runs 4 seconds). Compiled as: `g++ -std=gnu++11 -O2 foo.cc -lpthread` (Ubuntu 12.10 64bit, gcc 4.7.2)