yinhangjiasuanfa.cpp

操作系统课程设计之银行家算法

#include "iostream.h"
#include"stdlib.h"
#define N 5
int available[3]={3,3,2}; 
int max[6][3]={{7,5,3},{3,2,2},{9,0,2},{2,2,2},{4,3,3}}; 
int allocation[6][3]={{0,1,0},{2,0,0},{3,0,2},{2,1,1},{0,0,2}}; 
int need[6][3]={{7,4,3},{1,2,2},{6,0,0},{0,1,1},{4,3,1}}; 
int stay[3][3]; 
int request[3],process[5]; 
int i,j,p,kk,h=-1;//h为除去的进程号
void tu() 
{
	cout<<"----------------资源分配表-----------------"<<endl;
	cout<<"     Max    Allocation    Need   Available"<<endl;
	cout<<"PRO A B C      A B C      A B C    A B C"<<endl;
	for(i=0;i<N;i++) 
	{
		if(i!=h)
		{
			cout<<"P"<<i<<"  "; 
			for(j=0;j<=2;j++) 
				cout<<max[i][j]<<" ";
			cout<<"     ";
			for(j=0;j<=2;j++)
				cout<<allocation[i][j]<<" ";
			cout<<"     ";
			for(j=0;j<=2;j++) 
				cout<<need[i][j]<<" ";
			cout<<"   ";
			if(i==0)
				cout<<available[0]<<" "<<available[1]<<" "<<available[2];
			cout<<endl;
		}
	}
	cout<<"------------------------------------------"<<endl;
} 
int run() 
{
	int a=1; 
	for(i=0;i<=2;i++) 
	{
		if(need[p][i]<request[i])
		{
			a=0;break;
		} 
		if(available[i]<request[i]) 
		{
			a=0;break;
		}
	} 
	if(a==1)
	{
		for(i=0;i<=2;i++) 
		{
			stay[0][i]=allocation[p][i];
			allocation[p][i]+=request[i]; 
			stay[1][i]=need[p][i];
			need[p][i]-=request[i]; 
			stay[2][i]=available[i];
			available[i]-=request[i];
		} 
	} 
	return(a); 
} 
int test() 
{
	int work[3],finish[5]={0,0,0,0,0},a,k=0,t=0;
	for(i=0;i<N;i++) 
		if((h>=0)&&(i==h))
		{
			finish[i]=1;   kk=kk-1; 
		}
	for(i=0;i<=2;i++) 
		work[i]=available[i]; 
	while(1)
	{
		for(i=0;i<=4;i++) 
		{
			if(finish[i]==0) 
			{ 
				a=1; 
				for(j=0;j<=2;j++) 
					if(need[i][j]>work[j])
					{
						a=0; break;
					} 
				if(a==1)
				{
					finish[i]=1; 
					for(j=0;j<=2;j++)
						work[j]+=allocation[i][j]; 
					process[k]=i;k++; 
				}
			}
		}
		if(t==k) break; //循环一圈无可执行进程，阻塞跳出结束
		else t=k; 
		if(k==kk) break;
	}
	if(k==kk) return(1);
	else return(0);
} 
void main() 
{
	tu(); 
	while(1) 
	{
		int l=1;
		kk=N;
		while(l)
		{
			cout<<"*******************************************"<<endl;
			cout<<"输入选择的进程(P0-P5)[-1结束]:进程P";
		    cin>>p; 
			if(p==-1)  { cout<<"退出..."<<endl;  exit(0);}
	    	if(!(p<0||p>4||p==h)&&(p!=-1)) 
			{
				cout<<"需求A资源:";cin>>request[0];
	        	cout<<"需求B资源:";cin>>request[1];
		    	cout<<"需求C资源:";cin>>request[2];
				l=0;
			}
			if(l==1)  cout<<"选择进程错误，重新输入!"<<endl;
		}
		if(run()==0) 
		{
			cout<<"资源缺乏或需求错误！"<<"进程P"<<p<<"等待..."<<endl;
			cout<<"继续..."<<endl;
		}
		else if(test()==0)
		{
			cout<<"系统进入不安全状态！"<<"进程"<<p<<"等待..."<<endl;
			cout<<"继续..."<<endl;
			for(i=0;i<=2;i++)
			{
				allocation[p][i]=stay[0][i]; 
				need[p][i]=stay[1][i]; 
				available[i]=stay[2][i];
			}
		} 
		else
		{
			tu();
			cout<<"系统安全，存在安全序列：";
			for(i=0;i<kk-1;i++) 
				cout<<"P"<<process[i]<<"->";
			cout<<"P"<<process[kk-1]<<
				endl;
		} 
		if(need[p][0]==0&&need[p][1]==0&&need[p][2]==0) 
		{
			for(i=0;i<=2;i++) 
			{
				available[i]+=max[p][i]; 
			}
			h=p;
			cout<<"释放进程P"<<p<<"资源"<<endl;
			tu();
		}
	}
}