Lockfree ThreadPool implementation
Just some stylistic things that stick out to me:


I think it's a bit cumbersome to have all of this:

using std::cout ; using std::cin; using std::endl;
using std::mutex; using std::atomic;
using std::array; using std::function;


You're also still prefixing std:: in places, which defeats the purpose of having this.  Since you could always end up using something not already in this list, you might as well keep prefixing std:: as you're doing already, and remove all of that above.
Some of your indentation and semicolon placing are inconsistent.  In some places you indent or not, and in some places you have a space before the ending semicolon.  Keep the indentation consistent (you should utilize it) and choose what to do with all of your semicolons.
It would be more readable and maintainable to place the template statements on separate lines from the class or function, especially if either statement is lengthy:

template &lt;typename T&gt;
class Class
{
};




template &lt;typename T&gt;
void function()
{
}