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私はセマフォを理解しようとしていますが、私の実装では制約を与えて問題を解決することはできません。私は制約付きで6つのスレッドを使用しています。 3は0と1を待たなければならない。 4は起動前に1と2を待たなければなりません。 5は0と2を待つ必要があります。私はこの特定の問題に対してswitch文を使用することに決めましたが、どこが間違っているのか分からないようです。セマフォに関する問題
#include <iostream>
#include <sched.h>
#include <time.h>
#include <pthread.h>
#include "sem.h"
#include <cstdlib>
#define THREAD_COUNT 6
using namespace std;
extern sim_semaphore create_sim_sem(int) ;
extern void wait_sem (sim_semaphore) ;
extern void signal_sem (sim_semaphore) ;
pthread_mutex_t stdoutLock ;
int thrds_finished ;
// global sync variables
sim_semaphore support_ready[THREAD_COUNT] ;
sim_semaphore finished ;
/* These are global variable to represent threads created
dynamically. */
pthread_t thr[THREAD_COUNT] ;
/* This is included to facilitate adding random delays in the code
-- as a debugging aid. */
extern long random(void);
int checking = 0 ;
/* A data type - a struct (class) with an int field to represent
a thread ID. */
struct threadIdType
{
int id ;
};
void init()
{
if (0!=pthread_mutex_init(&stdoutLock, NULL))
{ cout << "MUTEX INITIALIZATION FAILURE!" << endl ;
exit(-1) ;}
thrds_finished = 0 ;
finished = create_sim_sem(0) ;
int count ;
for (count = 0; count < THREAD_COUNT ; count++)
{
support_ready[count] = create_sim_sem(0) ;
}
/* This initializes a random number generator */
srandom(time((time_t *) 0));
}
void rand_delay(int max)
{
int m_delay, j ;
m_delay = (int) random()%max ;
for (j=0; j<m_delay; j++) sched_yield();
}
void childMessage (int ID)
{
pthread_mutex_lock(&stdoutLock) ;
cout << "Child # " << ID
<< " has completed its assignment.\n" ;
pthread_mutex_unlock(&stdoutLock) ;
}
void * child(void * idPtr)
{
int me = ((threadIdType *) (idPtr))->id, temp ;
rand_delay(100) ;
// wait constraints
switch(me)
{
case 0: break ; // thread 0 just 'goes'
case 1: break ; // thread 1 just 'goes'
case 2: break ; // thread 2 just 'goes'
case 3: wait_sem (support_ready[0]) ;
wait_sem (support_ready[1]) ; // thread 3 waits for both 0 and 1
break ;
case 4: wait_sem (support_ready[1]) ;
wait_sem (support_ready[2]) ; // thread 4 waits for both 1 and 2
break ;
case 5: wait_sem (support_ready[0]) ;
wait_sem (support_ready[2]) ; // thread 5 waits for both 0 and 2
break ;
default: pthread_mutex_lock(&stdoutLock) ;
cout << "\n\nBAD VALUE TO CASE STATMENT!!\n\n" ;
pthread_mutex_unlock(&stdoutLock) ;
exit (-1); break ;
}
rand_delay(1000) ;
/* Next increment thrds_finished - to keep track
of how many child processes have finished their
tasks. */
/* Here put code you may need for protecting
thrds_finished. */
/* HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH */
/* HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH */
/* This code increments thrds_finished in a way
that magnifies the problem if the critical section
problem is not solved correctly. Of course,
do not change this part of the code. */
temp = thrds_finished ;
rand_delay(1000) ;
temp++ ;
rand_delay(1000) ;
thrds_finished = temp ;
/* Here put additional code you may need for protecting
thrds_finished. */
/* HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH */
/* HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH */
/* Announce completion of the assignment. */
childMessage(me) ;
switch(me)
{
case 0: signal_sem(support_ready[0]);
signal_sem(support_ready[0]); // thread 0 signals for threads 3 5
break ;
case 1: signal_sem(support_ready[1]) ; // thread 1 signals for 3 4
signal_sem(support_ready[1]) ;
break ;
case 2: signal_sem(support_ready[2]) ; // thread 2 signals for 4 5
signal_sem(support_ready[2]) ;
break;
case 3: break;
case 4: break;
case 5: signal_sem (finished); break; // thread 5 signals to the mother
default: pthread_mutex_lock(&stdoutLock) ;
cout << "\n\nBAD VALUE TO CASE STATMENT!!\n\n" ;
pthread_mutex_unlock(&stdoutLock) ;
exit (-1); break ;
}
pthread_exit ((void *)0) ;
}
// spawn child threads and waits for them to finish
void mother()
{
int i;
threadIdType * idPtr ;
/* Create child threads numbered 1 through 8. */
pthread_mutex_lock(&stdoutLock) ;
cout << "Mother Begins Spawning Threads.\n" << endl ;
pthread_mutex_unlock(&stdoutLock) ;
for (i = 0; i < THREAD_COUNT ; i++)
{
idPtr = new threadIdType ; /* allocate memory for struct */
idPtr->id = i ; /* records current index as the child's ID */
if (0!=pthread_create(&thr[i], NULL, child, (void *) idPtr))
{ pthread_mutex_lock(&stdoutLock) ; /* 'error out' code here */
cout << "THREAD CREATION FAILURE!" << endl ;
pthread_mutex_unlock(&stdoutLock) ;
exit(-1) ; }
if (0!=pthread_detach(thr[i]))
{ pthread_mutex_lock(&stdoutLock) ;/* 'error out' code here */
cout << "THREAD DETACHMENT FAILURE!" << endl ;
pthread_mutex_unlock(&stdoutLock) ;
exit(-1) ;}
}
rand_delay(3000) ; /* Simulate whatever may delay the mother thread */
pthread_mutex_lock(&stdoutLock) ;
cout << "Mother Finishes Spawning Threads.\n" << endl ;
pthread_mutex_unlock(&stdoutLock) ;
/* Some synchronization code is needed here to make the mother
behave correctly - she is not supposed to exit until after
all the children have finished their tasks. */
wait_sem (finished) ;
pthread_mutex_lock(&stdoutLock) ;
cout << "\nAll children have now reported that they finished.\n" ;
cout << "The value of the thrds_finished counter is: " ;
cout << thrds_finished << ".\n" ;
if (thrds_finished != THREAD_COUNT)
cout << "BAD COUNTER VALUE!! - Critical Section Problem Failure!!\n" ;
cout << "Mother exiting ... \n\n" ;
pthread_mutex_unlock(&stdoutLock) ;
return ;
}
int main()
{
cout << "\nWelcome to The Child Thread Workplace!\n\n" ;
/* This calls the function that performs initializations. */
init();
/* Execute the mother() function */
mother();
return 0 ;
}
このスレッドは、子スレッドを生成するマザー関数にシグナルを送信し、それらが終了するのを待つ必要があります。
私の問題は、私がコンパイルして実行したときに、すべてのスレッドが完了しているとは限らず、与えられた制約から同期していないように見えることです。
C++ 11を使用していますか？もしそうなら、私はそれに答えることができます – DeepakKg
はい私はこれがC++を使用していると信じています11 – sippycup