<li>The default logging timestamp precision has been changed from 6 digits

    to 9 digits, with a fixed format to ensure that 9 digits to the right of

    the decimal point are always printed.  Previously, default C++ iostream

    precision and formatting was used.

</li>

Controlling timestamp precision

*******************************

Timestamps are printed out in units of seconds.  When used with the default

|ns3| time resolution of nanoseconds, the default timestamp precision is 9 

digits, with fixed format, to allow for 9 digits to be consistently printed 

to the right of the decimal point.  Example:

::

  +0.000123456s RandomVariableStream:SetAntithetic(0x805040, 0)

When the |ns3| simulation uses higher time resolution such as picoseconds

or femtoseconds, the precision is expanded accordingly; e.g. for picosecond:

::

  +0.000123456789s RandomVariableStream:SetAntithetic(0x805040, 0)

When the |ns3| simulation uses a time resolution lower than microseconds,

the default C++ precision of 5 is used.

An example program at ``src\core\examples\sample-log-time-format.cc``

demonstrates how to change the timestamp formatting.

The maximum useful precision is 20 decimal digits, since Time is signed 64 

bits.

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */

/*

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation;

 *

 * This program is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU General Public License for more details.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

 */

/**

 * Example program that demonstrates how to replace the time printer.

 *

 * This program creates a sample object and schedules some methods to

 * occur at future times.  When run with no arguments, it prints out 

 * something like this:

 * \code

 * $ ./waf --run sample-log-time-format

 * RandomVariableStream:RandomVariableStream(0x184e3a0)

 * RandomVariableStream:UniformRandomVariable(0x184e3a0)

 * RandomVariableStream:SetStream(0x184e3a0, -1)

 * RandomVariableStream:SetAntithetic(0x184e3a0, 0)

 * +0.000000001s RandomVariableStream:SetAntithetic(0x184e3a0, 0)

 * +0.000000123s RandomVariableStream:SetAntithetic(0x184e3a0, 0)

 * +0.000123456s RandomVariableStream:SetAntithetic(0x184e3a0, 0)

 * +0.123456789s RandomVariableStream:SetAntithetic(0x184e3a0, 0)

 * RandomVariableStream:~RandomVariableStream(0x184e3a0)

 * \endcode

 *

 * These statements are printed out because of these two program

 * statements:

 *

 * \code

 * LogComponentEnable ("RandomVariableStream", LOG_LEVEL_ALL);

 * LogComponentEnableAll (LOG_PREFIX_TIME);

 * \endcode

 *

 * The first statement enables logging on the methods found in

 * random-variable-stream.cc.  The second prepends a time prefix

 * to logging statements.  Note that only those logging statements

 * occurring after Simulator::Run () is called have a time prefix;

 * this is because the time printer is only hooked to the simulator

 * once the simulator object is instantiated (after Simulator::Run ()

 * is called).

 *

 * To change the format, one can schedule (at simulation time 0) a 

 * replacement function for printing time.  This can be demonstrated

 * by setting the 'replace-time-printer' parameter to true:

 * \code

 * ./waf --run 'sample-log-time-format --replaceTimePrinter=1'

 * RandomVariableStream:RandomVariableStream(0x15fb080)

 * RandomVariableStream:UniformRandomVariable(0x15fb080)

 * RandomVariableStream:SetStream(0x15fb080, -1)

 * RandomVariableStream:SetAntithetic(0x15fb080, 0)

 * Replacing time printer function after Simulator::Run ()

 * 1e-09s RandomVariableStream:SetAntithetic(0x15fb080, 0)

 * 1.23e-07s RandomVariableStream:SetAntithetic(0x15fb080, 0)

 * 0.000123456s RandomVariableStream:SetAntithetic(0x15fb080, 0)

 * 0.123457s RandomVariableStream:SetAntithetic(0x15fb080, 0)

 * RandomVariableStream:~RandomVariableStream(0x15fb080)

 * \endcode

 *

 * In the above, the default C++ iostream precision is instead used

 * (which was the default for ns-3 versions 3.26 and earlier).

 *

 * In addition, the 'resolution' program argument allows one to experiment

 * with changing ns-3's time resolution from its default of Time::NS, such 

 * as Time::PS or Time::FS; the precision changes accordingly.

 *

 * The maximum useful precision is 20 decimal digits, since Time is 

 * signed 64 bits.

 */

#include "ns3/simulator.h"

#include "ns3/nstime.h"

#include "ns3/command-line.h"

#include "ns3/log.h"

#include "ns3/random-variable-stream.h"

using namespace ns3;

// Prior to ns-3.26, the time printer used default C++ iostream precision

// This function sets it back to the format used before ns-3.26

void

ReplacementTimePrinter (std::ostream &os)

{

  os << Simulator::Now ().GetSeconds () << "s";

}

void

ReplaceTimePrinter (void)

{

  std::cout << "Replacing time printer function after Simulator::Run ()" << std::endl;

  LogSetTimePrinter (&ReplacementTimePrinter);

}

int main (int argc, char *argv[])

{

  bool replaceTimePrinter = false;

  std::string resolution = "Time::NS";

  LogComponentEnable ("RandomVariableStream", LOG_LEVEL_ALL);

  LogComponentEnableAll (LOG_PREFIX_TIME);

  std::map<std::string, Time::Unit> resolutionMap = {{"Time::US", Time::US}, {"Time::NS", Time::NS}, {"Time::PS", Time::PS}, {"Time::FS", Time::FS}};

  CommandLine cmd;

  cmd.AddValue ("replaceTimePrinter", "replace time printing function", replaceTimePrinter);

  cmd.AddValue ("resolution", "time resolution", resolution);

  cmd.Parse (argc, argv);

  auto search = resolutionMap.find (resolution);

  if (search != resolutionMap.end ())

    {

      Time::SetResolution (search->second);

    }

  Ptr<UniformRandomVariable> uniformRv = CreateObject<UniformRandomVariable> ();

  if (replaceTimePrinter)

    {

      Simulator::Schedule (Seconds (0), &ReplaceTimePrinter);

    }

  Simulator::Schedule (NanoSeconds (1), &UniformRandomVariable::SetAntithetic, uniformRv, false);

  Simulator::Schedule (NanoSeconds (123), &UniformRandomVariable::SetAntithetic, uniformRv, false);

  Simulator::Schedule (NanoSeconds (123456), &UniformRandomVariable::SetAntithetic, uniformRv, false);

  Simulator::Schedule (NanoSeconds (123456789), &UniformRandomVariable::SetAntithetic, uniformRv, false);

  Simulator::Run ();

  Simulator::Destroy ();

}

    obj = bld.create_ns3_program('sample-log-time-format', ['core'])

    obj.source = 'sample-log-time-format.cc'

#include <iomanip>