整理 | 夕颜

代码解析部分来源于 | xuyuanwai（ID:xxuyuanwai）

近日，有一位B站up主上传了一段视频，用计算机仿真程序模拟了冠状病毒传播的场景，并提醒大众不要出门活动。这个视频一经推出就得到大家的关注，让人们感受到计算机程序在这场抗疫战争中可以做出的贡献。

不久后，这条视频的up主Ele实验室又放出了本程序的GitHub开源链接，公布了这个程序的相关代码。目前，这个名为VirusBroadcast的项目已获得1000多star，作者也在简介中强调了这个基于java的模拟仿真程序由于启动仓促，还有一些不足，如果有好的想法或者能提供相关数据支持的朋友可以请提issues。

B站地址：https://www.bilibili.com/video/av86478875

GitHub地址：https://github.com/KikiLetGo/VirusBroadcast

此后，有人解析了VirusBroadcast的程序代码，下面我们就来看看它是如何一步步实现的吧：

这个程序主要利用“高斯分布”算法，简单的模拟病毒传播的场景。

它由以下程序片段构成

1、病毒对象

public class Virus {}

2、床位【隔离对象】

public class Bed extends Point{    public Bed(int x, int y) {        super(x, y);    }    private boolean isEmpty=true;public boolean isEmpty() {        return isEmpty;    }    public void setEmpty(boolean empty) {        isEmpty = empty;    }}

3、主要参数【初始状态】，假设没有隔离，潜伏期为一天

public class Constants {    public static int ORIGINAL_COUNT=50;//初始感染数量    public static float BROAD_RATE = 0.8f;//传播率    public static float SHADOW_TIME = 1;//潜伏时间    public static int HOSPITAL_RECEIVE_TIME=10;//医院收治响应时间    public static int BED_COUNT=0;//医院床位    public static float u=0.99f;//流动意向平均值}

4、医院对象，随机分布，产生床位

public class Hospital {    private int x=800;    private int y=110;private int width;    private int height=606;    public int getWidth() {        return width;    }    public int getHeight() {        return height;    }public int getX() {        return x;    }public int getY() {        return y;    }private static Hospital hospital = new Hospital();    public static Hospital getInstance(){        return hospital;    }    private Point point = new Point(800,100);    private List<Bed> beds = new ArrayList<>();private Hospital() {        if(Constants.BED_COUNT==0){            width=0;            height=0;        }        int column = Constants.BED_COUNT/100;        width = column*6;        for(int i=0;i<column;i++){            for(int j=10;j<=610;j+=6){                Bed bed = new Bed(point.getX()+i*6,point.getY()+j);                beds.add(bed);            }        }    }public Bed pickBed(){        for(Bed bed:beds){            if(bed.isEmpty()){                return bed;            }        }        return null;    }}

5、流动目的地

public class MoveTarget {    private int x;    private int y;    private boolean arrived=false;public MoveTarget(int x, int y) {        this.x = x;        this.y = y;    }public int getX() {        return x;    }public void setX(int x) {        this.x = x;    }public int getY() {        return y;    }public void setY(int y) {        this.y = y;    }public boolean isArrived() {        return arrived;    }public void setArrived(boolean arrived) {        this.arrived = arrived;    }}

6、人员【流动及感染】

public class Person {    private City city;    private int x;    private int y;    private MoveTarget moveTarget;    int sig=1;    double targetXU;    double targetYU;    double targetSig=50;    public interface State{        int NORMAL = 0;        int SUSPECTED = NORMAL+1;        int SHADOW = SUSPECTED+1;        int CONFIRMED = SHADOW+1;        int FREEZE = CONFIRMED+1;        int CURED = FREEZE+1;    }public Person(City city, int x, int y) {        this.city = city;        this.x = x;        this.y = y;        targetXU = 100*new Random().nextGaussian()+x;        targetYU = 100*new Random().nextGaussian()+y;}    public boolean wantMove(){        double value = sig*new Random().nextGaussian()+Constants.u;        return value>0;    }private int state=State.NORMAL;public int getState() {        return state;    }public void setState(int state) {        this.state = state;    }public int getX() {        return x;    }public void setX(int x) {        this.x = x;    }public int getY() {        return y;    }public void setY(int y) {        this.y = y;    }    int infectedTime=0;    int confirmedTime=0;    public boolean isInfected(){        return state>=State.SHADOW;    }    public void beInfected(){        state = State.SHADOW;        infectedTime=MyPanel.worldTime;    }public double distance(Person person){        return Math.sqrt(Math.pow(x-person.getX(),2)+Math.pow(y-person.getY(),2));    }private void freezy(){        state = State.FREEZE;    }    private void moveTo(int x,int y){        this.x+=x;        this.y+=y;    }    private void action(){        if(state==State.FREEZE){            return;        }        if(!wantMove()){            return;        }        if(moveTarget==null||moveTarget.isArrived()){double targetX = targetSig*new Random().nextGaussian()+targetXU;            double targetY = targetSig*new Random().nextGaussian()+targetYU;            moveTarget = new MoveTarget((int)targetX,(int)targetY);}int dX = moveTarget.getX()-x;        int dY = moveTarget.getY()-y;        double length=Math.sqrt(Math.pow(dX,2)+Math.pow(dY,2));if(length<1){            moveTarget.setArrived(true);            return;        }        int udX = (int) (dX/length);        if(udX==0&&dX!=0){            if(dX>0){                udX=1;            }else{                udX=-1;            }        }        int udY = (int) (dY/length);        if(udY==0&&udY!=0){            if(dY>0){                udY=1;            }else{                udY=-1;            }        }if(x>700){            moveTarget=null;            if(udX>0){                udX=-udX;            }        }        moveTo(udX,udY);}private float SAFE_DIST = 2f;public void update(){        if(state>=State.FREEZE){            return;        }        if(state==State.CONFIRMED&&MyPanel.worldTime-confirmedTime>=Constants.HOSPITAL_RECEIVE_TIME){            Bed bed = Hospital.getInstance().pickBed();            if(bed==null){                System.out.println("隔离区没有空床位");            }else{                state=State.FREEZE;                x=bed.getX();                y=bed.getY();                bed.setEmpty(false);            }        }        if(MyPanel.worldTime-infectedTime>Constants.SHADOW_TIME&&state==State.SHADOW){            state=State.CONFIRMED;            confirmedTime = MyPanel.worldTime;        }action();List<Person> people = PersonPool.getInstance().personList;        if(state>=State.SHADOW){            return;        }       for(Person person:people){           if(person.getState()== State.NORMAL){               continue;           }           float random = new Random().nextFloat();           if(random<Constants.BROAD_RATE&&distance(person)<SAFE_DIST){               this.beInfected();           }       }    }}

7、汇总人数

public class PersonPool {    private static PersonPool personPool = new PersonPool();    public static PersonPool getInstance(){        return personPool;    }List<Person> personList = new ArrayList<Person>();public List<Person> getPersonList() {        return personList;    }private PersonPool() {        City city = new City(400,400);        for (int i = 0; i < 5000; i++) {            Random random = new Random();            int x = (int) (100 * random.nextGaussian() + city.getCenterX());            int y = (int) (100 * random.nextGaussian() + city.getCenterY());            if(x>700){                x=700;            }            Person person = new Person(city,x,y);            personList.add(person);        }    }}

8、分布点

public class Point {    private int x;    private int y;public Point(int x, int y) {        this.x = x;        this.y = y;    }public int getX() {        return x;    }public void setX(int x) {        this.x = x;    }public int getY() {        return y;    }public void setY(int y) {        this.y = y;    }}

9、显示面板，设置色块【红色：感染   黄色：潜伏  绿色：安全】

public class MyPanel extends JPanel implements Runnable {   private int pIndex=0;    public MyPanel() {        this.setBackground(new Color(0x444444));    }@Override    public void paint(Graphics arg0) {        super.paint(arg0);        //draw border        arg0.setColor(new Color(0x00ff00));        arg0.drawRect(Hospital.getInstance().getX(),Hospital.getInstance().getY(),                Hospital.getInstance().getWidth(),Hospital.getInstance().getHeight());        List<Person> people = PersonPool.getInstance().getPersonList();        if(people==null){            return;        }        people.get(pIndex).update();        for(Person person:people){switch (person.getState()){                case Person.State.NORMAL:{                    arg0.setColor(new Color(0xdddddd));}break;                case Person.State.SHADOW:{                    arg0.setColor(new Color(0xffee00));}break;                case Person.State.CONFIRMED:                case Person.State.FREEZE:{                    arg0.setColor(new Color(0xff0000));}break;            }            person.update();            arg0.fillOval(person.getX(), person.getY(), 3, 3);}        pIndex++;        if(pIndex>=people.size()){            pIndex=0;        }    }public static int worldTime=0;    @Override    public void run() {        while (true) {this.repaint();try {                Thread.sleep(100);                worldTime++;            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}

10、主程序【运行】

public class Main {    public static void main(String[] args) {        MyPanel p = new MyPanel();        Thread panelThread = new Thread(p);        JFrame frame = new JFrame();        frame.add(p);        frame.setSize(1000, 800);        frame.setLocationRelativeTo(null);        frame.setVisible(true);        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);        panelThread.start();List<Person> people = PersonPool.getInstance().getPersonList();        for(int i=0;i<Constants.ORIGINAL_COUNT;i++){            int index = new Random().nextInt(people.size()-1);            Person person = people.get(index);while (person.isInfected()){                index = new Random().nextInt(people.size()-1);                person = people.get(index);            }            person.beInfected();        }    }}

首先，假设某个城市初始感染人数为50，医院床位为0【人员可随意流动】，那么城市很快会被感染，感染分布如下：

此时修改流动参数，控制人员流动，则疫情传播较慢，但也会传播开来

如果此时建立隔离区，将医院的床位数设为200张，并不随意走动则疫情很快得到有效控制

如果此时建立隔离区，将医院的床位数设为200张，但随意走动则隔离床位会很快被用完，病毒又开始扩散

此时，我们隔离区变得足够大，医务人员增加床位数到1000，则病毒也会得到有效控制

这位解析者还提醒大家，不随意走动是建立隔离区是在短时间内有效控制病毒的最好方式，现在病毒防疫进入关键时期，此时此刻我们一定要听从党中央的安排，好好呆在家里，不要随意跟人接触，早日打赢病毒阻击战，让我们的生活步入正轨。

推荐阅读 

☞百度地图可查49城患者活动轨迹；谷歌申请新操作系统商标；VS Code 1.42发布 | 极客头条

☞天才？骗子？解析Deep Tech

☞AAAI 2020论文解读：商汤科技发布新视频语义分割和光流联合学习算法

☞远程办公众生相：“云”吃饭、被窝打卡、梳妆台编程......

☞2020 年，云游戏将爆发？各大科技公司云游戏布局大曝光！

☞SIM卡交换攻击盗币猖獗，比特币从业者如何自保？

你点的每一个在看，我认真当成了喜欢