NS-3学习之main-random-topology.cc_ns3 randomrectanglepositionallocato-优快云博客

本文链接：https://blog.youkuaiyun.com/Jerry_liu20080504/article/details/122604848

/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/*
 * Copyright (c) 2006,2007 INRIA
 *
 * 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
 *
 */

#include "ns3/core-module.h"
#include "ns3/mobility-module.h"

using namespace ns3;

/**
 * Function called when there is a course change
 * \param context event context
 * \param position a pointer to the mobility model
 */
static void CourseChange(std::string context,
		Ptr<const MobilityModel> position) {
	Vector pos = position->GetPosition();
	std::cout << "context:" << context << " ,time:" << Simulator::Now()
			<< ", pos=" << position << ", x=" << pos.x << ", y=" << pos.y
			<< ", z=" << pos.z << std::endl;
}

int main(int argc, char *argv[]) {
	CommandLine cmd(__FILE__);
	cmd.Parse(argc, argv);

	NodeContainer c;
	c.Create(100);

	MobilityHelper mobility;
	/*
	 * ns-3: ns3::RandomDiscPositionAllocator Class Reference
	 * https://www.nsnam.org/docs/release/3.35/doxygen/classns3_1_1_random_disc_position_allocator.html
	 *  Rho:极坐标极径
	 *  UniformRandomVariable:均匀分布随机数生成器
	 *  个人理解，是以X和Y为坐标原点，以该原点为圆心，以Rho（随机数）为半径的圆内随机生成节点。
	 */
	mobility.SetPositionAllocator("ns3::RandomDiscPositionAllocator", "X",
			StringValue("100.0"), "Y", StringValue("100.0"), "Rho",
			StringValue("ns3::UniformRandomVariable[Min=90|Max=100]"));

//	mobility.SetMobilityModel("ns3::ConstantPositionMobilityModel");
	//2D随即游走模型
	mobility.SetMobilityModel("ns3::RandomWalk2dMobilityModel", "Bounds",
			RectangleValue(Rectangle(-5000, 5000, -5000, 5000)));
	mobility.Install(c);

	Config::Connect("/NodeList/*/$ns3::MobilityModel/CourseChange",
			MakeCallback(&CourseChange));

	Simulator::Stop(Seconds(100.0));

	Simulator::Run();

	Simulator::Destroy();
	return 0;
}

源码出处：NS-3 3.35 源码包中的src/mobility/examples/main-random-topology.cc

个人按照标题理解该示例应该是想建立一个随机的拓扑图，如果目的是这个，那该例子无可厚非，做到了。但是，例子中有一段代码：
Config::Connect("/NodeList/*/$ns3::MobilityModel/CourseChange", MakeCallback(&CourseChange));
该代码应该是在节点位置或者运动速度发生变化时回调函数CourseChange 被调用
（参考：
(50条消息) NS-3学习笔记 5_hhhparty的博客-优快云博客
https://blog.youkuaiyun.com/hhhparty/article/details/78189789
）
但是，移动模型设置为mobility.SetMobilityModel("ns3::ConstantPositionMobilityModel");静态的，也就是说节点位置是固定的。所以，--vis 运行启动该例子后，发现根本没有触发CourseChange 函数。尝试将移动模型修改为2D 游走模型后，触发了CourseChange函数，同时可以从控制台输出看到每个节点的位置变化情况。

运行效果如图：