using boost thread pool executor submit method - c++

Question

I am trying to learn boost thread pool.
not working, hope to find help here.
Some strange thing happens in the following code, when I
create an executor ea and
use async to start it till it finishes the submitted functions,
then submit other functions to this first executor ea but I don't start it,
and then go make another executor ea3 of the same type (basic_thread_pool) and different number of threads (1)
and start the 2nd executor ea3 with async,
it first executes the 1st executer ea, then the second executor ea3!
Although I just use ea3 as argument to async.
Why does this happen? and how do I prevent the execution of ea?
Does nameless scope has an effect??
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#define BOOST_THREAD_VERSION 4
#define BOOST_THREAD_PROVIDES_EXECUTORS
#define BOOST_THREAD_USES_LOG_THREAD_ID
#define BOOST_THREAD_QUEUE_DEPRECATE_OLD
#include <boost/lexical_cast.hpp> // for lexical_cast
#include <boost/thread.hpp>
#include <boost/thread/caller_context.hpp> // for BOOST_CONTEXTOF, caller_context_t, operator<<
#include <boost/thread/executors/basic_thread_pool.hpp> // for basic_thread_pool
#include <boost/thread/executors/executor.hpp> // for executor
#include <boost/thread/executors/executor_adaptor.hpp> // for executor_adaptor
#include <iostream> // for operator<<, cout, endl, ..
#include <chrono> // for operator "" ms, operator "" s
#include <thread> // for sleep_for
#include <string>
#include <vector>
static boost::mutex stdout_mutex;
template <typename A, typename B = std::string> static inline void trace(A const &a, B const& b = "") {
boost::lock_guard<boost::mutex> lock(stdout_mutex);
std::cout << a << b << std::endl;
}
static inline void trace(boost::caller_context_t const &ctx) { trace(boost::lexical_cast<std::string>(ctx)); }
namespace {
using namespace std::chrono_literals;
using std::this_thread::sleep_for;
void p1() { trace(BOOST_CONTEXTOF); sleep_for(20ms); }
void p2() { trace(BOOST_CONTEXTOF); sleep_for(1s); }
int f1() { trace(BOOST_CONTEXTOF); sleep_for(100ms); return 1; }
}
void submit_some(boost::executor &tp) {
for (int i = 0; i < 3; ++i) { tp.submit(p2); }
for (int i = 0; i < 3; ++i) { tp.submit(p1); }
}
int test_executor_adaptor() {
trace(BOOST_CONTEXTOF);
try {
boost::executor_adaptor<boost::basic_thread_pool> ea(4);
trace(BOOST_CONTEXTOF);
submit_some(ea);
{
boost::future<int> t1 = boost::async(ea, &f1);
trace(BOOST_CONTEXTOF);
trace(" t1= ", t1.get()); // problem unknown on running showing thread result before running code
std::vector<boost::future<int> > vt1;
for (int i = 0; i < 4; i++) {
vt1.push_back(boost::async(ea, &f1)); // here async starts all closures already submitted to ea
// then submit f1 to all threads in ea to work
// asynchronusly so end result will be 7 already submitted
// and 4 more f1 and return futures to only the last 4 f1
// which is submitted by async
}
for (auto &e : vt1) {
auto e_value = e.get();
trace("vt1 e_value = ", e_value);
}
}
submit_some(ea);
{
boost::executor_adaptor<boost::basic_thread_pool> ea3(1);
boost::future<int> t1 = boost::async(ea3, &f1);
std::vector<boost::future<int> > vt1;
for (int i = 0; i < 4; i++) {
vt1.push_back(
boost::async(ea3, &f1)); // here async starts all closures already submitted to ea
// then submit f1 to all threads in ea to work
// asynchronusly so end result will be 7 already submitted
// and 4 more f1 and return futures to only the last 4 f1
// which is submitted by async
}
for (auto &e : vt1) {
trace("vt1 e_value = ", e.get());
}
}
}
catch (std::exception &ex) { trace("ERROR= ", ex.what()); return 1; }
catch (...) { trace("UNKNOWN EXCEPTION"); return 2; }
trace(BOOST_CONTEXTOF);
return 0;
}
int main() {
trace(BOOST_CONTEXTOF);
return test_executor_adaptor();
}
i think that basic_thread_pool use event loop,
and this event loop is singleton,
so when i define another basic_thread_pool it just uses the same event loop,and in turn when getting futures it run all tasks on the event loop including those of other thread pools,
this is a guess but i cant find proof for it from the impl code
in case this guess is right how can i make different event loop for each basic_thread_pool.
i use msvc 14
thanks