yinhangjia.cpp

C++编写的关于操作系统中死锁问题的银行家算法

#include "iostream.h"
#define P 5         
#define N 4         
#define FALSE 0
#define TRUE  1
int M=5;            
int AVAILABLE[N]={1,5,2,0};  
int MAX[P][N]={{7,5,3,2},{2,3,4,3},{4,3,3,2},{5,2,3,4},{3,5,3,2}};
    
int ALLOCATION[P][N]={{0},{0},{0},{0}};
   
int NEED[P][N]={{0,0,0,2},{0,7,5,0},{1,0,0,2},{0,0,2,0},{1,6,4,2}};
   
int Request[N]={0,0,0,0}; 

void showdata( )
   {  int i,j,t;
      cout<<"      系统可用的资源数: "<<endl<<endl;
      cout<<" ";
      for (i=0;i<M;i++)
        {  for (j=0;j<N;j++)
              if (NEED[i][j]!=0)
                  break;
              if(j==N)
                for(t=0;t<N;t++)
                    AVAILABLE[t]= AVAILABLE[t]+MAX[i][t];
        }  
      for (j=0;j<N;j++)
         cout<<" 资源"<<j<<":"<<AVAILABLE[j];
      cout<<" "<<endl<<endl;
      cout<<"    各进程资源最大需求量:"<<endl<<endl;
      for (i=0;i<M;i++)
        {
          cout<<"进程"<<i<<":";
           for (j=0;j<N;j++)
             { if (NEED[i][j]!=0)
                   break;
             }
           if (j==N )   cout<<"该进程已结束" ;
           else  for (j=0;j<N;j++)
                  cout<<" 资源"<<j<<":"<<MAX[i][j];
           cout<<endl;
        }
      cout<<endl;
      cout<<"    各进程尚需要的资源量:"<<endl<<endl;
      for (i=0;i<M;i++)
        {
          cout<<"进程"<<i<<":";
          for (j=0;j<N;j++)
              { if(NEED[i][j]!=0)
                    break;
              }
          if(j==N ) cout<<"该进程已结束" ;
          else  for (j=0;j<N;j++)
                 cout<<" 资源"<<j<<":"<<NEED[i][j];
          cout<<endl;
       }
     cout<<endl;
     cout<<"    各进程已得到的资源量: "<<endl<<endl;
     for (i=0;i<M;i++)
       {
         cout<<"进程"<<i<<":";
         for (j=0;j<N;j++)
             { if (NEED[i][j]!=0)
                   break;
             }
         if(j==N )  cout<<"该进程已结束" ;
         else  for (j=0;j<N;j++)
                 cout<<" 资源"<<j<<":"<<ALLOCATION[i][j];
         cout<<endl;
       }
     cout<<endl;
   }

void changdata(int k)
  {
    int j;
    for (j=0;j<N;j++)
       {
        AVAILABLE[j]=AVAILABLE[j]-Request[j];
        ALLOCATION[k][j]=ALLOCATION[k][j]+Request[j];
        NEED[k][j]=NEED[k][j]-Request[j];
       }
  }

void comebackdata(int k)
  {
     int j;
     for (j=0;j<N;j++)
        {
       	   AVAILABLE[j]=AVAILABLE[j]+Request[j];
           ALLOCATION[k][j]=ALLOCATION[k][j]-Request[j];
           NEED[k][j]=NEED[k][j]+Request[j];
        }
  }

int check(int s)               
  {
    int WORK,FINISH[P],temp[P];
    int i,j,k=0;
    for(i=0;i<M;i++)
        FINISH[i]=FALSE;
    for(j=0;j<N;j++)
      {
        WORK=AVAILABLE[j];
        i=s;
        while(i<M)
          {
            if (FINISH[i]==FALSE&&NEED[i][j]<=WORK)
                {  WORK=WORK+ALLOCATION[i][j];
                   FINISH[i]=TRUE;
                   temp[k]=i;
                   k++;
                   i=0;
                }
            else  i++;               
          }
        for(i=0;i<M;i++)
          if(FINISH[i]==FALSE)
            {
             cout<<endl;
             cout<<" 系统不安全!!!本次资源申请不成功!!!"<<endl<<endl;
             return 1;
            }
      }
    cout<<endl;
    cout<<"  经安全性检查，系统安全，本次分配成功。"<<endl<<endl;
    cout<<"  本次安全序列：";
    for(i=0;i<M;i++) 
      cout<<"进程"<<temp[i]<<"->";
    cout<<endl<<endl;
    return 0;
}

void main()
  {
    int i,j,a;
    char flag='Y';
    char hold='y';
    while (hold=='y'||hold=='Y')
      {  cout<<"功能选择："<<endl;
         cout<<"  1. 输入新的进程资源需求向量"<<endl;
         cout<<"  2. 为某进程申请资源,并检测是否是安全状态"<<endl;
         cout<<"  3. 查看系统资源及各进程情况"<<endl;
         cout<<"  4. 退出银行家算法的模拟实验"<<endl;
         cout<<"  请选择: 【  】\b\b";
         cin>>a;
         switch (a)
          { case 1 : cout<<"进程"<<M<<"各类资源最大需求量 "<<endl;
               for (j=0;j<N;j++)
                { cout<<" 资源"<<j<<": ";
                  cin>>MAX[M][j];
                  NEED[M][j]=MAX[M][j];
                  if(MAX[M][j]>AVAILABLE[j])
                   {
                    cout<<" 进程"<<M<<"资源最大需求量大于"<<j<<"类资源的资源量!";
                    cout<<endl<<" 申请不合理，出错!请重新选择!"<<endl<<endl;
                    flag='N';
                    M--;
                    break;
                  }
               }
               M++;
               break;
             case 2:  i=-1;
              while(i<0||i>=M)
              {
               cout<<" 请输入需申请资源的进程（从0到"<<M-1<<"，否则重输入!）:";
               cin>>i;
               if(i<0||i>=M) cout<<" 输入的进程号不存在，重新输入!"<<endl;
              }
              cout<<" 请输入进程"<<i<<"申请的资源数"<<endl;
              for (j=0;j<N;j++)
              { cout<<" 资源"<<j<<": ";
                cin>>Request[j];
                if(Request[j]>NEED[i][j])
                  {
                   cout<<" 进程"<<i<<"申请的资源数大于进程"<<i<<"还需要"<<j<<"类资源的资源量!";
                   cout<<endl<<" 申请不合理，出错!请重新选择!"<<endl<<endl;
                   flag='N';
                   break;
                  }
                else
                  { if(Request[j]>AVAILABLE[j])
                    {
                     cout<<" 进程"<<i<<"申请的资源数大于系统可用"<<j<<"类资源的资源量!";
                     cout<<" 申请不合理，出错!请重新选择!"<<endl<<endl;
                     flag='N';
                     break;
                    }
                  }
               } 
              if(flag=='Y'||flag=='y')
               {
                  changdata(i);
                  if(check(i))
                   {
                    comebackdata(i);
                    showdata( );
                   }
              else
               showdata( );
             }
          break;
        case 3 : showdata(); break;
        case 4 : hold='n'; break;
        default :cout <<"  输入错误，请重新输入!!!"<<endl;
      }
    }
 }