Segmentation fault with NullMessageSimulatorImpl

Rui Cunha

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Jun 15, 2022, 9:54:43 AM6/15/22

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I was trying to run some tests with MPI and NS-3.35 and I encounter some issues when using the NullMessageSimulatorImpl algorithm.

When using the DistributedSimulatorImpl everything works as expected, but when switching to the NullMessageSimulatorImpl segmentation faults occur. This happens even with just a simple example with just two hosts and a Ping application.

Looking at the gdb output it appears the segmentation occurs in the ns3::NullMessageMpiInterface::SendNullMessage method when trying to send the MPI message.

I suspect this could be a bug, but before opening an issue I would like to make sure this is not a problem in my end.

Is anyone able to use NullMessageSimulatorImpl?

Rui Cunha

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Jun 15, 2022, 9:56:06 AM6/15/22

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Simple example to reproduce:

/* -*- Mode: C++; c-file-style: "gnu"; indent-tabs-mode:nil; -*- */
#include "ns3/object.h"
#include "ns3/point-to-point-helper.h"
#include <ns3/core-module.h>
#include <ns3/csma-module.h>
#include <ns3/internet-apps-module.h>
#include <ns3/internet-module.h>
#include <ns3/network-module.h>
#include "ns3/mpi-module.h"

using namespace ns3;

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

bool nullmsg = false;

CommandLine cmd;
cmd.AddValue ("nullmsg", "Enable the use of null-message synchronization", nullmsg);
cmd.Parse (argc, argv);

if (nullmsg)
{
GlobalValue::Bind ("SimulatorImplementationType",
StringValue ("ns3::NullMessageSimulatorImpl"));
}
else
{
GlobalValue::Bind ("SimulatorImplementationType",
StringValue ("ns3::DistributedSimulatorImpl"));
}

MpiInterface::Enable (&argc, &argv);

Ptr<Node> node0 = CreateObject<Node> (0);
Ptr<Node> node1 = CreateObject<Node> (1);

NodeContainer hosts;
hosts.Add (node0);
hosts.Add (node1);

NetDeviceContainer hostDevices;

PointToPointHelper p2pHelper;
hostDevices = p2pHelper.Install (hosts);

// Install the TCP/IP stack into hosts nodes
InternetStackHelper internet;
internet.Install (hosts);

// Set IPv4 host addresses
Ipv4AddressHelper ipv4helpr;
Ipv4InterfaceContainer hostIpIfaces;
ipv4helpr.SetBase ("10.1.1.0", "255.255.255.0");
hostIpIfaces = ipv4helpr.Assign (hostDevices);

if (MpiInterface::GetSystemId () == 0)
{
// Configure ping application between hosts
V4PingHelper pingHelper = V4PingHelper (hostIpIfaces.GetAddress (1));
pingHelper.SetAttribute ("Verbose", BooleanValue (true));
ApplicationContainer pingApps = pingHelper.Install (hosts.Get (0));
pingApps.Start (Seconds (0));
}

// Run the simulation
Simulator::Stop (Seconds (10));
Simulator::Run ();
Simulator::Destroy ();

MpiInterface::Disable ();
}

Tom Henderson

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Jun 20, 2022, 1:27:45 PM6/20/22

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Thanks for the report; I was able to confirm there is an issue and will ask someone to look into it. It is being tracked here: