PV操作(哲学家问题和生产者-消费者问题)剖析

CRITICAL_SECTIONfork[5];//定义五个临界变量，代表五更筷子
intmain(intargc,char*argv[])
{
HANDLEhthread[5];
inti;
intarg[5];
intcount = 5;
longa=0;
unsignedlongretval;
InitializeCriticalSection(&crout);} Nhomakorabea}
//等待所有线程结束
retval = WaitForMultipleObjects(5,hthread,true,INFINITE);//等待多个线程
for(a=0;a<30000000;a++);
if(retval ==WAIT_FAILED)
{
cerr<<"wait error,error code: "<<GetLastError()<<endl;
//初始化临界变量
for(i=0;i<5;i++)
{
InitializeCriticalSection(fork + i);
}
//创建五个哲学家
for(i = 0; i<5;i++)
{
arg[i] = i;
hthread[i] = CreateThread(NULL, 0, philosopher, (void*)(arg+i), 0,NULL);
{
longa=0;
for(a=0;a<30000000;a++);
EnterCriticalSection(&crout);
cout<<"process "<<who<<str<<endl;
LeaveCriticalSection(&crout);
}
操作截图
PV
解决方法一：
实现思想，我们在产生足够的产品后，唤醒消费者把生产的产品全部消耗，让后在唤醒生产者生产商品。
semaphore full=0; /*记录缓冲区中满的槽数*/
semaphore buf[N]; /*有N个槽数的缓冲区buf[N]，并实现循环缓冲队列*/
Sleep(1);
EnterCriticalSection(fork +k);//获得左边的筷子
//print(k," take left");
EnterCriticalSection(fork + (k+ 1)%5);//获得右边的筷子
//print(k," take right");
}
voidprint(intwho,constchar*str)
Sleep(1);
//Sleep((rand() %100) *5);
}
voideating(intk)
{
longa=0;
for(a=0;a<30000000;a++);
print(k," is eating...");
//Sleep((rand()%100) *5);
Sleep(1);
LeaveCriticalSection(fork + (k+1)%5);//放下右边的筷子
}
for(i = 0; i<5;i++)
{
for(a=0;a<30000000;a++);
if(CloseHandle(hthread[i]) ==false)//关闭句柄
{
cerr <<"error while close thread "<<i<<endl;
cerr <<"error code: "<<GetLastError()<<endl;
while(true)
{
thinking(n);
waiting(n);
eating(n);
}
print(n," is out!");
returnn;
}
voidthinking(intk)
{
longa=0;
for(a=0;a<30000000;a++);
print(k," is thinking...");
//print(k," give left");
LeaveCriticalSection(fork +k);//放下左边的筷子
//print(k," give right");
}
voidwaiting(intk)
{
longa=0;
for(a=0;a<30000000;a++);
print(k," is waiting...");
}
}
return0;
}
DWORDWINAPIphilosopher(LPVOIDlpParameter)
{
longa=0;
intn = ((int*)lpParameter)[0];
for(a=0;a<30000000;a++);
print(n," is in!");
//srand(time(NULL));
PV
给每个哲学家编号，规定奇数号的哲学家先拿他的左筷子，然后再去拿他的右筷子；而偶数号的哲学家则相反。这样总可以保证至少有一个哲学家可以进餐。
#include<windows.h>
#include<iostream>
#include<process.h>
#include<cstdlib>
#include<ctime>
for(a=0;a<30000000;a++);
if( hthread[i] ==INVALID_HANDLE_VALUE)//如果线程创建失败返回-1
{
cerr <<"error while create thread "<< i <<endl;
cerr <<"error code : "<< GetLastError() <<endl;
usingnamespacestd;
DWORDWINAPIphilosopher(LPVOIDlpParameter);
voidthinking(int);
voideating(int);
voidwaiting(int);
voidprint(int,constchar*);
//全局变量
CRITICAL_SECTIONcrout;//这个变量用来保证输出时不会竞争
/*用信号量解决生产者－消费者问题*/
//解决方法生产者生产10间产品，唤醒消费者，消费完后，唤醒生产者
#include <STDIO.H>
#define N 10
typedef int semaphore; /*信号量是一种特殊的整型变量*/
semaphore mutex=1; /*互斥访问*/
semaphore empty=N; /*记录缓冲区中空的槽数*/