银行家算法.cpp

银行家算法,实现了避免死锁的算法,是比较高级的程序

#include "string.h"  
#include "iostream.h"  
#define M 5 //总进程数  
#define N 10 //总资源数  
#define FALSE 0  
#define TRUE 1  

//M个进程对N类资源最大资源需求量  
int MAX[M][N]={{7,5,3,5,6,7,3,4,7,4},{3,4,8,7,6,3,5,6,2,2},{4,4,2,5,7,6,5,4,7,2},{2,5,3,4,4,4,3,4,2,2},{4,7,8,6,2,3,5,5,3,3}};  
//系统可用资源数  
int AVAILABLE[N]={10,10,10,10,10,10,10,10,10,10};  
//M个进程已经得到N类资源的资源量  
int ALLOCATION[M][N]={0};  
//M个进程还需要N类资源的资源量  
int NEED[M][N]={{7,5,3,5,6,7,3,4,7,4},{3,4,8,7,6,3,5,6,2,2},{4,4,2,5,7,6,5,4,7,2},{2,5,3,4,4,4,3,4,2,2},{4,7,8,6,2,3,5,5,3,3}};   
int Request[N]={0};  


void main()  
{  
int i=0,j=0;  
char flag='Y';  
void showdata();  
void changdata(int);  
void rstordata(int);  
int chkerr(int);  

showdata();  
while(flag=='Y'||flag=='y')  
{  
i=-1;  
while(i<0||i>=M)  
{  
cout<<" 请输入需申请资源的进程号（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<<"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(chkerr(i))  
{  
rstordata(i);  
showdata();  
}  
else  
showdata();  
}  
else  
showdata();  
cout<<endl;  
cout<<" 是否继续银行家算法演示,按'Y'或'y'键继续,按'N'或'n'键退出演示: ";  
cin>>flag;  
}  
}  


void showdata()  
{  
int i,j;  
cout<<" 系统可用的资源数为:"<<endl<<endl;  
cout<<" ";  
for (j=0;j<N;j++)cout<<" 资源"<<j<<": "<<AVAILABLE[j];  
cout<<endl;  
cout<<endl;  
cout<<" 各进程还需要的资源量:"<<endl<<endl;  
for (i=0;i<M;i++)  
{  
cout<<"进程"<<i<<":";  
for (j=0;j<N;j++)cout<<" 资源"<<j<<": "<<NEED[i][j];  
cout<<endl;  
}  
cout<<endl;  
cout<<" 各进程已经得到的资源量: "<<endl<<endl;  
for (i=0;i<M;i++)  
{  
cout<<"进程"<<i<<":";  
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 rstordata(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 chkerr(int s)  
{  
int WORK,FINISH[M],temp[M];  
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;  
cout<<endl;  
return 1;  
}  
}  
cout<<endl;  
cout<<" 经安全性检查，系统安全，本次分配成功。"<<endl;  
cout<<endl;  
cout<<" 本次安全序列：";  
for(i=0;i<M;i++)cout<<"进程"<<temp[i]<<"->";  
cout<<endl<<endl;;  
return 0;  
};