Why does the function with arguments have errors?

[mirro187]

Error C2672: "CTPL ::thread_pool::push" : no matching overloaded function found
Error C2780: "STD ::future : CTPL ::thread_pool::push(F &&)" : one parameter should be input, but two are provided
Error C2893: function template "STD ::future CTPL ::thread_pool::push(F &&,Rest &&...) "specialty
Error C2672: "STD ::vector< STD ::future, STD ::allocator<_Ty> : >::emplace_back" : overloaded function not found

#include "ctpl_stl.h"
#include "iostream"
#include "string"

void f(int j)
{
std::cout << j << std::endl;

}

int main(int argc, char **argv) {

ctpl::thread_pool p(8 /* two threads in the pool */);

std::vector< std::future<int> > results;

for (int i = 0; i < 8; ++i) {
	results.emplace_back(
		p.push(f, i));
}

for (auto && result : results)
	std::cout << result.get() << ' ';
std::cout << std::endl;
getchar();

return 0;

}

[mirro187]

What's the right thing to do?

[nicolas-chan-42]

Hi I am new to CTPL too but I think that I have the answer to your question.

For functions to be pushed into thread_pool, there has to be an int argument as its first argument, the rest being the actual arguments needed by your function. So it translate to the following:

void f(int j)
should become
void f(int id, int j)

Then your program should work.

For functions with no argument by itself, e.g.

void print_something()
{
    std::cout << "HelloWorld!";
}

You will need to make it (in CTPL version):

void print_something(int id)  // Notice the added argument.
{
    std::cout << "HelloWorld!";
}

This seems to be applicable to all kinds of functions that you will passed into thread_pool, i.e. you need an int argument as the first argument, regardless of functor, function pointer, lambda, etc.

Hope this helps...