哲学家就餐问题在 linux 上的程序实现

来源：互联网发布：分析软件有哪些编辑：程序博客网时间：2024/06/05 13:27

与windows 平台的实现类似，
程序上稍有不同。
PhilosopherDining.cpp
#include <iostream>
#include <string>
#include <pthread.h>
#include <unistd.h>
#include <semaphore.h>
#include "RasUtil.h"
using namespace std;
const unsigned int PHILOSOPHER_NUM=5;
const char THINKING=1;
const char HUNGRY=2;
const char DINING=3;
// each fork has a semaphore
sem_t semph[PHILOSOPHER_NUM];
// Mutex for printing
pthread_mutex_t mutex;
void* philosopherProc(void* param);
int main(int argc, char* argv[])
{
int i;
srand(getpid());
pthread_t philosopherThread[PHILOSOPHER_NUM];
int phId[PHILOSOPHER_NUM];
pthread_mutex_init(&mutex, NULL);
for (i=0; i<PHILOSOPHER_NUM; i++)
{
         phId[i] = i;
  sem_init(&semph[i], 0, 1);
  pthread_create(&philosopherThread[i], NULL, philosopherProc, (void*)(&phId[i]));
  usleep(50);
}
sleep(3);
return 0;
}
void* philosopherProc(void* param)
{
int myid;
char idStr[128];
char stateStr[128];
char mystate;
int ret;
unsigned int leftFork;
unsigned int rightFork;
myid = *((int*)(param));
RasUtil::intToStr(myid, idStr);

cout << "philosopher " << myid << " begin......" << endl;
//usleep(10);
// initial state is THINKING
mystate = THINKING;
leftFork = (myid) % PHILOSOPHER_NUM;
rightFork = (myid + 1) % PHILOSOPHER_NUM;
while (true)
{
  switch(mystate)
  {
  case THINKING:
   // changing my state
   mystate = HUNGRY;
   strcpy(stateStr, "HUNGRY");
   break;
  case HUNGRY:
   strcpy(stateStr, "HUNGRY");
   // first test the left fork ...
   ret = sem_trywait(&semph[leftFork]);
   if (ret == 0)

{
    // left fork is ok, take it up !
    // then test the right fork ...
    ret = sem_trywait(&semph[rightFork]);
    if (ret == 0)
    {
     // right fork is also ok !
     // changing my state
     mystate = DINING;
     strcpy(stateStr, "DINING");
    }
    else
    {
     // right fork is being used by others, so I must put down
     // the left fork.
     sem_post(&semph[leftFork]);
    }
   }
   break;
  case DINING:
   // put down both the left and right fork
   sem_post(&semph[leftFork]);
   sem_post(&semph[rightFork]);
   // changing my state
   mystate = THINKING;
   strcpy(stateStr, "THINKING");
   break;
  }
  // print my state
  pthread_mutex_lock(&mutex);
  cout << "philosopher " << myid << " is : " << stateStr << endl;
  pthread_mutex_unlock(&mutex);

  // sleep a random time : between 1 - 5 s
  int sleepTime;
  sleepTime = 1 + (int)(5.0*rand()/(RAND_MAX+1.0));
  usleep(sleepTime*10);
}
}
RasUtil.h : 完成整数转换为字符串
#ifndef _RasUtil_h_
#define _RasUtil_h_
class RasUtil
{
public:
static inline void intToStr(int i, char* str);

};

inline void RasUtil::intToStr(int i, char* str)
{
    int dec;
    int sign;
    char* p;
    p = ecvt(i, 10, &dec, &sign);

strcpy(str, p);
str[dec] = 0;
}
#endif