snooze.cpp

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/*****************************************************************************
** Includes
*****************************************************************************/

#include <iostream>
#include <cmath>
#include <ecl/threads/priority.hpp>
#include <ecl/time_lite/functions.hpp>
#include <ecl/time/snooze.hpp>
#include <ecl/time/timestamp.hpp>

/*****************************************************************************
** Namespaces
*****************************************************************************/

namespace ecl {
namespace benchmarks {

/*****************************************************************************
** Using
*****************************************************************************/

using ecl::Duration;
using ecl::Snooze;
using ecl::StandardException;

/*****************************************************************************
** Classes
*****************************************************************************/

class LogSnooze : public Snooze {

public:
        LogSnooze(const long &ms) : Snooze(Duration(0,ms*1000000L)), count(0), avg(0.0), avg_noise(0.0), max(0), period_ms(ms) {};

        // Need to run this at least 10 times before the average is close
        // to correct.
        void log() {
                ecl::epoch_time(time_actual);
                latency = (time_actual.tv_nsec - time_value.tv_nsec)/1000000.0; // convert to ms
                if ( count == 0 ) {
                        avg = latency;
                } else {
                        avg = 0.9*avg + 0.1*latency;
                        avg_noise = 0.9*avg_noise + 0.1*fabs(latency-avg);
                }
                if ( latency > max ) { max = latency; }
                ++count;
        }

        void printLog() {
                std::cout << "Loop period [ms]:     " << period_ms << std::endl;
                std::cout << "Average latency [ms]: " << avg << std::endl;
                std::cout << "Maximum latency [ms]: " << max << std::endl;
        }

private:
        /*********************
        ** Logging Variables
        **********************/
        timespec time_actual;
        double latency;
        int count;
        double avg,avg_noise;
        double max;
        long period_ms;
};


} // namespace benchmarks
} // namespace ecl

/*****************************************************************************
** Using
*****************************************************************************/

using namespace ecl::benchmarks;

/*****************************************************************************
** Main program
*****************************************************************************/

int main() {

        try {
                ecl::set_priority(ecl::RealTimePriority4);
        } catch ( StandardException &e ) {
                // dont worry about it.
        }

    std::cout << std::endl;
    std::cout << "***********************************************************" << std::endl;
    std::cout << "                   Snooze Latency" << std::endl;
    std::cout << "***********************************************************" << std::endl;
    std::cout << "* " << std::endl;
    std::cout << "* Latency is the absolute time behind where it should be." << std::endl;
    std::cout << "* This is only a factor for the first snooze loop." << std::endl;
    std::cout << "*" << std::endl;
    std::cout << "* Latency noise is more important. After the first loop," << std::endl;
    std::cout << "* with an ideal noise value of zero, the loop will time" << std::endl;
    std::cout << "* exactly as you specify. Practically, this is not the case," << std::endl;
    std::cout << "* but you should get good results from this without having" << std::endl;
    std::cout << "* to use system timers. Use with loops which need to be" << std::endl;
    std::cout << "* 5ms or over. Faster loops really require a RTOS." << std::endl;
    std::cout << "* " << std::endl;
    std::cout << "*****************************************************************" << std::endl;
    std::cout << std::endl;
    std::cout << "Looping commencing..." << std::endl;

    LogSnooze snooze(30);
    snooze.initialise(); // Get it ready to start looping.
    for(int i = 0; i < 100; ++i ) {
        snooze();
        snooze.log();
    }
    snooze.printLog();

    std::cout << std::endl;
    std::cout << "***********************************************************" << std::endl;
    std::cout << "                      Passed" << std::endl;
    std::cout << "***********************************************************" << std::endl;
    std::cout << std::endl;

    return 0;
}