1024 * 1024 / sizeof(int)

     void f(const std::string& file_name)
     {
	std::ifstream stream(file_name, std::ios::in);
           std::list<int> list;

	int x;
	while(stream >> x)
	{
                 list.push_back(x);
                 if (list.size() == 1000 * 1000 * 1000)
                 {
                        // что-то сделать с list
                        list.resize(0);
                 }
	}
            
            // и здесь обработать оставшийся list
 
	
	stream.close();
      }

#include <fstream>
#include <iterator>
#include <string>
#include <vector>
#include <sstream>
#include <time.h>

void buf1()
{
	const clock_t begin_time = clock();
	
	std::vector<int> v(1000000);
	
	int cnt = -1;
	std::ifstream file;
	char buf[1024 * 64];
	
	file.rdbuf()->pubsetbuf(buf, sizeof buf);
	file.open("./input.txt");
	
	for (std::string line; getline(file, line);) {
		v[++cnt] = std::stoi(line);
	}
	
	std::cout << float( 1000 * (clock () - begin_time )) /  CLOCKS_PER_SEC << std::endl;
}

void buf2()
{
	const clock_t begin_time = clock();
	
	std::string file_name("./input.txt");
	
	std::ifstream stream(file_name, std::ios::in);
	std::list<int> list;

	
	std::vector<int> v(10000000);
	int idx = -1;

	int x;
	while(stream >> x)
	{
		v[++idx] =  x;
	}
	
	stream.close();
	
	std::cout << float( 1000 * (clock () - begin_time )) /  CLOCKS_PER_SEC << std::endl;
}

int main(int argc, _TCHAR* argv[])
{
	buf1();
	buf2();
	while (1);
	return 0;
}

   // вместо
   //for (std::string line; getline(file, line);) {
   //	v[++cnt] = std::stoi(line);
   //}

   // записал
   int x;
   while(file >> x)
   {
      v[++cnt] =  x;
   }

void buf3()
{
	const clock_t begin_time = clock();
	
	std::ifstream ifs("./input_file.txt", std::ios::binary);
	char buff[32 * 512];

	for (int i = 0; ; ++i){
		ifs.read(buf, sizeof(buff) / sizeof(*buff));
		for (int j = 0; j < 32 * 512; ++j){
			if (buff[j] == '-'){
			} else if(buff[j] == '\n') {
			} else {
				// Обрабатываем '0' - '9'
			}
		}
		//std::cout << std::endl;
	}
	
	std::cout << float( 1000 * (clock () - begin_time )) /  CLOCKS_PER_SEC << std::endl;
}