操作系统实验_利用银行家算法避免死锁

//
//操作系统实验:
//利用银行家算法避免死锁
//

#include "iostream.h"
#include "iomanip.h"

#define max_source 20
#define max_process 100

int available[max_source];
int max[ max_process ][ max_source ];
int allocation[ max_process ][max_source ];
int need[ max_process ][ max_source ];
int request[ max_source ];
int requestPID;
int source;    //当前系统所具有的资源种类
int process;   //当前系统的进程数

//返回值
//1:表示请求的资源>还分配的资源
//2:表示请求的资源>系统剩余的资源
//3:表示不存在安全序列
//0:成功
int banker( int securitySequence[] )
{
 int i , j , k;
 
 for( i = 0 ; i < source ; i++ )
 {
  if( request[i] > need[requestPID][i] )
   return 1;
 }

 for( i = 0 ; i < source ; i++ )
 {
  if( request[i] > available[i] )
   return 2;
 }

 for( i = 0 ; i < source ; i++ )
 {
  available[i] -= request[i];
  allocation[requestPID][i] += request[i];
  need[requestPID][i] -= request[i];
 }

 int finish[ max_process ] = { 0 };
 int work[ max_source ];
 int currSelect;
 for( i = 0 ; i < source ; i++ )
  work[i] = available[i];
 for( k = 0 ; k < process ; k++ )
 {
  bool flag = false;
  ////输出过程
  //cout<<"work"<<endl;
  //for( i = 0 ; i < source ; i++ )
  // cout<<setw(5)<<work[i];
  //
  //cout<<endl<<"need"<<endl;
  for( i = 0 ; i < process && !flag ; i++ )
  {
   if( finish[i] == 0 )
   {
    flag = true;
    for( j = 0 ; j < source && flag; j++ )
    {
     //
     //cout<<setw(5)<<need[i][j];
     if( need[i][j] > work[j] )
      flag = false;
    }
    //
    //cout<<endl;
   }
   currSelect = i;
  }
  if( !flag )
  {
   for( j = 0 ; j < source ; j++ )
   {
    available[j] += request[j];
    allocation[requestPID][j] -= request[j];
    need[requestPID][j] += request[j];
   }
   return 3;
  }
  finish[currSelect] = k+1;
  //
  //cout<<"allocation"<<endl;
  for( j = 0 ; j < source ; j++ )
  {
   work[j] += allocation[currSelect][j];
   //
   //cout<<setw(5)<<allocation[currSelect][j];
  }
  //
  //cout<<endl<<"当前选择"<<currSelect<<endl;
  //cout<<"----------------------------------------"<<endl;
 }
 for( i = 0 ; i < process ; i++ )
 {
  j = 0;
  while( finish[j] != i + 1 )
   j++;
  securitySequence[i] = j;
 }

 return 0;
}

//setCurrentState
void setCurrentState()
{
 source = 3;
 process = 5;
 int a[] = { 3 , 3 , 2 };
 int m[][ max_source ] = {
    { 7 , 5 , 3 } ,
    { 3 , 2 , 2 } ,
    { 9 , 0 , 2 } ,
    { 2 , 2 , 2 } ,
    { 4 , 3 , 3 } ,
    };
 int al[][ max_source ] = {
    { 0 , 1 , 0 } ,
    { 2 , 0 , 0 } ,
    { 3 , 0 , 2 } ,
    { 2 , 1 , 1 } ,
    { 0 , 0 , 2 }
    };
 int re[] = { 1 , 0 , 2 };
 int i , j;

 cout<<"当前可用资源数:"<<endl;
 for( i = 0 ; i < source ; i++ )
 {
  available[i] = a[i];
  cout<<setw(5)<<available[i];
 }
 cout<<endl<<endl;

 cout<<"当前进程所需资源的最大数:"<<endl;
 for( i = 0 ; i < process ; i++ )
 {
  for( j = 0 ; j < source ; j++ )   
  {
   max[i][j] = m[i][j];
   cout<<setw(5)<<max[i][j];
  }
  cout<<endl;
 }
 cout<<endl;

 cout<<"当前进程已分配到资源数:"<<endl;
 for( i = 0 ; i < process ; i++ )
 {
  for( j = 0 ; j < source ; j++ )   
  {
   allocation[i][j] = al[i][j];
   cout<<setw(5)<<allocation[i][j];
  }
  cout<<endl;
 }
 cout<<endl;

 cout<<"当前进程还需分配的资源数:"<<endl;
 for( i = 0 ; i < process ; i++ )
 {
  for( j = 0 ; j < source ; j++ )   
  {
   need[i][j] = max[i][j] - allocation[i][j];
   cout<<setw(5)<<need[i][j];
  }
  cout<<endl;
 }
 cout<<endl;

 requestPID = 1;
 cout<<"进程 "<<requestPID<<" 请求的资源向量:"<<endl;
 for( i = 0 ; i < source ; i++ )
 {
  request[i] = re[i];
  cout<<setw(5)<<request[i];
 }
 cout<<endl<<endl;
}

void main()
{
 //为进行一次模拟实验
 //设置系统的当前状态
 setCurrentState();

 int securitySequence[ max_process ] = { 0 };

 cout<<"调用银行家算法..."<<endl;
 int error = banker( securitySequence );
 if( !error )
 {
  cout<<"可以响应该请求，响应后存在安全序列:"<<endl;
  for( int i = 0 ; i < process ; i++ )
   cout<<setw(5)<<securitySequence[i];
  cout<<endl;
 }
 else
 {
  cout<<"无法响应该请求."<<endl;
 }
}