std::condition_variable is a class for waiting for thread execution until the condition is satisfied.
Used in combination with std::mutex.
I tried the wait() function in std::condition_variable.
This is combined with std::unique_lock<std::mutex>.
I thought of the following specifications.
As shown in the figure, create multiple threads.
All threads are in Wait state.
Then let the threads run one by one.
Make mutex and condition_variable management class.
The created thread is waited using condition_variable.
Sleeping for 1 second immediately after passing Wait.
Then execution request is made to the next thread.
struct turn_thread
{
std::mutex f_mtx_
std::condition_variable f_cond_
std::vector<String> f_strings_
void processing_from_standby(int process_num)
{
std::unique_lock<std::mutex> ulk(f_mtx_
//After waiting, execute processing.
f_cond_.wait(ulk
f_strings_.push_back(TimeToStr(Now()) + " process_num=" + IntToStr(process_num
//1 second sleep.
std::this_thread::sleep_for(std::chrono::seconds(1
//Only one of the waiting threads is executed.
f_cond_.notify_one
}
inline void start_and_join(std::vector<std::thread>& vthreads1)
{
f_cond_.notify_one
for (auto& th:vthreads1)
{
th.join
}
}
Thread creation function
It is a button event of C++Builder.
We create 10 threads, but they are all waited.
Thereafter, to perform one single thread start_and_join() function.
void __fastcall TForm1::Button1Click(TObject *Sender)
{
//
TDateTime dt1{Now()};
std::vector<std::thread> vthreads1
turn_thread turn1
for (int i = 0 i < 10 i++)
{
vthreads1.push_back(std::thread([i, &turn1](){
turn1.processing_from_standby(i
}));
}
turn1.start_and_join(vthreads1
for (auto& str1: turn1.f_strings_)
{
Memo1->Lines->Append(str1
}
dt1 = Now() - dt1
Memo1->Lines->Append(TimeToStr(dt1
}
//---------------------------------------------------------------------------
Execution result
Threads are executed in an irregular way one by one.
