cpu_timer.cc

Go to the documentation of this file.

// ======================================================================
//
// cpu_timer: Measure the cpu and wallclock elapsed times
//
// ======================================================================

#include "cetlib/cpu_timer.h"

#include "cetlib_except/exception.h"
#include <cerrno>
#include <sys/resource.h>

using namespace cet;

namespace {

  // ======================================================================
  // helpers:

  timeval
  real_now()
  {
    timeval now;
    gettimeofday(&now, 0);
    return now;
  }

  timeval
  cpu_now()
  {
    rusage theUsage;
    if (getrusage(RUSAGE_SELF, &theUsage) != 0) {
      throw exception("cpu_timer", "Failure in get_current_stats") << errno;
    }

    timeval now;
    now.tv_sec = theUsage.ru_stime.tv_sec + theUsage.ru_utime.tv_sec;
    now.tv_usec = theUsage.ru_stime.tv_usec + theUsage.ru_utime.tv_usec;
    return now;
  }

  double
  operator-(timeval const& t1, timeval const& t2)
  {
    double constexpr microsec_per_sec{1E-6};
    return t1.tv_sec - t2.tv_sec + (t1.tv_usec - t2.tv_usec) * microsec_per_sec;
  }
}

// ======================================================================
// accessors:

double
cpu_timer::elapsed_real_time() const
{
  return real_now() - start_real_time_;
}

double
cpu_timer::elapsed_cpu_time() const
{
  return cpu_now() - start_cpu_time_;
}

double
cpu_timer::accumulated_real_time() const
{
  return is_stopped() ? accumulated_real_time_ :
                        accumulated_real_time_ + elapsed_real_time();
}

double
cpu_timer::accumulated_cpu_time() const
{
  return is_stopped() ? accumulated_cpu_time_ :
                        accumulated_cpu_time_ + elapsed_cpu_time();
}

// ======================================================================
// mutators:

void
cpu_timer::start()
{
  if (!is_stopped())
    return;
  start_real_time_ = real_now();
  start_cpu_time_ = cpu_now();
  is_running_ = true;
}

void
cpu_timer::stop()
{
  if (!is_running())
    return;
  accumulated_real_time_ += elapsed_real_time();
  accumulated_cpu_time_ += elapsed_cpu_time();
  is_running_ = false;
}

void
cpu_timer::reset()
{
  accumulated_real_time_ = 0.0;
  accumulated_cpu_time_ = 0.0;
}

// ======================================================================