boost thread example

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  • Gary Wessle
    #1

    boost thread example


    Hi

    given the Boost thread example here
    http://www-eleves-isia.cma.fr/documentation/BoostDoc/boost_1_29_0/libs/thread/example/thread.cpp


    the code below attempts to run the example
    thread while giving the user a prompt for data input.
    I am failing to get the prompt while the thread is running, what am I
    doing wrong?

    thanks

    *************** *************** *************** *************** ****
    #include <boost/thread/thread.hpp>
    #include <boost/thread/xtime.hpp>
    #include <iostream>
    using namespace std;

    struct thread_alarm
    {
    thread_alarm(in t secs) : m_secs(secs) { }
    void operator()()
    {
    boost::xtime xt;
    boost::xtime_ge t(&xt, boost::TIME_UTC );
    xt.sec += m_secs;

    boost::thread:: sleep(xt);

    std::cout << "alarm sounded..." << std::endl;
    }

    int m_secs;
    };

    int main(){
    int secs = 5;
    std::cout << "setting alarm for 5 seconds..." << std::endl;
    for( ;; ) {
    cout << "type a number please:" << endl;
    int opt;
    cin >opt;
    switch( opt ) {
    case ( 1 ): {
    thread_alarm alarm(secs);
    boost::thread thrd(alarm);
    thrd.join();
    break;
    }
    case (99 ): cout << "Exiting ...\n"; break;
    default: cout << "you typed " << opt << endl;
    }
    }
    }
    Tags: None
    • Alf P. Steinbach
      #2
      Re: boost thread example

      * Gary Wessle:
      Hi
      >
      given the Boost thread example here
      http://www-eleves-isia.cma.fr/documentation/BoostDoc/boost_1_29_0/libs/thread/example/thread.cpp

      >
      the code below attempts to run the example
      thread while giving the user a prompt for data input.
      I am failing to get the prompt while the thread is running, what am I
      doing wrong?
      >
      thanks
      >
      *************** *************** *************** *************** ****
      #include <boost/thread/thread.hpp>
      #include <boost/thread/xtime.hpp>
      #include <iostream>
      using namespace std;
      >
      struct thread_alarm
      {
      thread_alarm(in t secs) : m_secs(secs) { }
      void operator()()
      {
      boost::xtime xt;
      boost::xtime_ge t(&xt, boost::TIME_UTC );
      xt.sec += m_secs;
      >
      boost::thread:: sleep(xt);
      >
      std::cout << "alarm sounded..." << std::endl;
      }
      >
      int m_secs;
      };
      >
      int main(){
      int secs = 5;
      std::cout << "setting alarm for 5 seconds..." << std::endl;
      for( ;; ) {
      cout << "type a number please:" << endl;
      int opt;
      cin >opt;
      switch( opt ) {
      case ( 1 ): {
      thread_alarm alarm(secs);
      boost::thread thrd(alarm);
      thrd.join();
      break;
      }
      case (99 ): cout << "Exiting ...\n"; break;
      default: cout << "you typed " << opt << endl;
      }
      }
      }
      The code above says to wait for the thread to finish before going on
      with issuing the next prompt. From your description it seems the
      program is doing exactly what the code says it should do. Btw., beware
      of doing unsynchronized i/o in threads.

      --
      A: Because it messes up the order in which people normally read text.
      Q: Why is it such a bad thing?
      A: Top-posting.
      Q: What is the most annoying thing on usenet and in e-mail?

        Comment

        • Gary Wessle
          #3
          Re: boost thread example

          "Alf P. Steinbach" <alfps@start.no writes:
          * Gary Wessle:
          Hi
          given the Boost thread example here
          http://www-eleves-isia.cma.fr/documentation/BoostDoc/boost_1_29_0/libs/thread/example/thread.cpp

          the code below attempts to run the example
          thread while giving the user a prompt for data input. I am failing
          to get the prompt while the thread is running, what am I
          doing wrong?
          thanks
          *************** *************** *************** *************** ****
          #include <boost/thread/thread.hpp>
          #include <boost/thread/xtime.hpp>
          #include <iostream>
          using namespace std;
          struct thread_alarm
          {
          thread_alarm(in t secs) : m_secs(secs) { }
          void operator()()
          {
          boost::xtime xt;
          boost::xtime_ge t(&xt, boost::TIME_UTC );
          xt.sec += m_secs;
          boost::thread:: sleep(xt);
          std::cout << "alarm sounded..." << std::endl;
          }
          int m_secs;
          };
          int main(){
          int secs = 5;
          std::cout << "setting alarm for 5 seconds..." << std::endl;
          for( ;; ) {
          cout << "type a number please:" << endl;
          int opt;
          cin >opt;
          switch( opt ) {
          case ( 1 ): {
          thread_alarm alarm(secs);
          boost::thread thrd(alarm);
          thrd.join();
          break;
          }
          case (99 ): cout << "Exiting ...\n"; break;
          default: cout << "you typed " << opt << endl;
          }
          }
          }
          >
          The code above says to wait for the thread to finish before going on
          with issuing the next prompt. From your description it seems the
          program is doing exactly what the code says it should do. Btw.,
          beware of doing unsynchronized i/o in threads.
          I need the code to issue the next prompt without waiting for the
          thread to finish so that the user can select another "opt" while the
          first thread job is still going.

            Comment

            • Gary Wessle
              #4
              Re: boost thread example

              "Alf P. Steinbach" <alfps@start.no writes:
              * Gary Wessle:
              Hi
              given the Boost thread example here
              http://www-eleves-isia.cma.fr/documentation/BoostDoc/boost_1_29_0/libs/thread/example/thread.cpp

              the code below attempts to run the example
              thread while giving the user a prompt for data input. I am failing
              to get the prompt while the thread is running, what am I
              doing wrong?
              thanks
              *************** *************** *************** *************** ****
              #include <boost/thread/thread.hpp>
              #include <boost/thread/xtime.hpp>
              #include <iostream>
              using namespace std;
              struct thread_alarm
              {
              thread_alarm(in t secs) : m_secs(secs) { }
              void operator()()
              {
              boost::xtime xt;
              boost::xtime_ge t(&xt, boost::TIME_UTC );
              xt.sec += m_secs;
              boost::thread:: sleep(xt);
              std::cout << "alarm sounded..." << std::endl;
              }
              int m_secs;
              };
              int main(){
              int secs = 5;
              std::cout << "setting alarm for 5 seconds..." << std::endl;
              for( ;; ) {
              cout << "type a number please:" << endl;
              int opt;
              cin >opt;
              switch( opt ) {
              case ( 1 ): {
              thread_alarm alarm(secs);
              boost::thread thrd(alarm);
              thrd.join();
              break;
              }
              case (99 ): cout << "Exiting ...\n"; break;
              default: cout << "you typed " << opt << endl;
              }
              }
              }
              >
              The code above says to wait for the thread to finish before going on
              with issuing the next prompt. From your description it seems the
              program is doing exactly what the code says it should do. Btw.,
              beware of doing unsynchronized i/o in threads.
              >
              if I comment out the line
              thrd.join();
              it gives me the desired effect, is that the correct way to do it?

                Comment

                • dasjotre
                  #5
                  Re: boost thread example


                  Gary Wessle wrote:
                  Hi
                  struct thread_alarm
                  {
                  thread_alarm(in t secs) : m_secs(secs) { }
                  void operator()()
                  {
                  boost::xtime xt;
                  boost::xtime_ge t(&xt, boost::TIME_UTC );
                  xt.sec += m_secs;
                  >
                  boost::thread:: sleep(xt);
                  cout is not synchronized, it might
                  overlap with main thread's output

                  <snip>
                  std::cout << "alarm sounded..." << std::endl;
                  }
                  <snip>
                  switch( opt ) {
                  case ( 1 ): {
                  thread_alarm alarm(secs);
                  boost::thread thrd(alarm);
                  join will wait till thrd terminates, that doesn't seem
                  to be what you want
                  thrd.join();
                  break;
                  }
                  case (99 ): cout << "Exiting ...\n"; break;
                  default: cout << "you typed " << opt << endl;
                  I believe you want the alarm to sound if the user
                  takes more than 5 seconds to type

                  In that case you will need to cancel the alarm
                  here. your current implementation of thread_alarm
                  doesn't provide such functionality

                  maybe looping around a flag for a fraction
                  of alarm time and then changing the flag
                  to exit the loop would do.

                  general idea:

                  struct thread_alarm
                  {
                  bool loop_;
                  thread_alarm(in t secs) : m_secs(secs) , loop_(true){ }

                  void cancel(){ loop_= false; }

                  void operator()()
                  {
                  while(loop_ && m_secs)
                  {
                  boost::xtime xt;
                  boost::xtime_ge t(&xt, boost::TIME_UTC );
                  // sleep a second at a time
                  xt.sec += 1;
                  --m_secs;
                  boost::thread:: sleep(xt);
                  }
                  if(loop_)
                  std::cout << "alarm sounded..." << std::endl;
                  }

                  int m_secs;
                  };

                    Comment

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