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Producer consumer pthreads program not finishing


Producer consumer pthreads program not finishing

By : Nachtfalter
Date : November 21 2020, 03:00 PM
I wish this helpful for you So I have to make a program that uses 4 producer threads and 4 consumer threads, with an array that holds 10 random numbers at a time. Once that array is full, the producer must wait until those 10 numbers are consumed by the consumer, and then the consumer waits for the array to be full again. I have to do this with 1000 random numbers.
code :
    if (bufCounter == BSIZE){
        isFull = true;
        isEmpty = false;
    }
    if (bufCounter == 0){
        isEmpty = true;
        isFull = false;
    }   


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pthreads producer-consumer deadlock

pthreads producer-consumer deadlock


By : katie biernat
Date : March 29 2020, 07:55 AM
it helps some times You used cond_empty in both sides for the wait. You signal (but never wait on) cond_full.
producer-consumer problem with pthreads

producer-consumer problem with pthreads


By : user3091529
Date : March 29 2020, 07:55 AM
it should still fix some issue Both the consumer and producer does a sleep(rand()) which will sleep for a random number of seconds between 0 and MAX_INT, in the example you give the main thread will terminate after 10 seconds. If the rand() value of the producers are above 10 they will never have the chance produce anything.
Producer Consumer program using semaphores and pthreads

Producer Consumer program using semaphores and pthreads


By : ext3063
Date : March 29 2020, 07:55 AM
it fixes the issue Maybe you should take the Compiler warnings more serious. Incorrect types and undefined functions are usually shown as warning...
I haven't checked the Logic of your program, but the principle should work:
code :
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include </usr/include/semaphore.h>

// for sleep
#include <unistd.h>

#define BUFF_SIZE   5           /* total number of slots */
#define NP          3           /* total number of producers */
#define NC          3           /* total number of consumers */
#define NITERS      4           /* number of items produced/consumed */

typedef struct
{
    int buf[BUFF_SIZE];   /* shared var */
    int in;               /* buf[in%BUFF_SIZE] is the first empty slot */
    int out;              /* buf[out%BUFF_SIZE] is the first full slot */
    sem_t full;           /* keep track of the number of full spots */
    sem_t empty;          /* keep track of the number of empty spots */

    // use correct type here
    pthread_mutex_t mutex;          /* enforce mutual exclusion to shared data */
} sbuf_t;

sbuf_t shared;


void *Producer(void *arg)
{
    int i, item, index;

    index = (int)arg;


    for (i=0; i < NITERS; i++)
    {

        /* Produce item */
        item = i;

        /* Prepare to write item to buf */

        /* If there are no empty slots, wait */
        sem_wait(&shared.empty);
        /* If another thread uses the buffer, wait */
        pthread_mutex_lock(&shared.mutex);
        shared.buf[shared.in] = item;
        shared.in = (shared.in+1)%BUFF_SIZE;
        printf("[P%d] Producing %d ...\n", index, item);
        fflush(stdout);
        /* Release the buffer */
        pthread_mutex_unlock(&shared.mutex);
        /* Increment the number of full slots */
        sem_post(&shared.full);

        /* Interleave  producer and consumer execution */
        if (i % 2 == 1) sleep(1);
    }
    return NULL;
}

void *Consumer(void *arg)
{
    int i, item, index;

    index = (int)arg;
    for (i=NITERS; i > 0; i--) {
        sem_wait(&shared.full);
        pthread_mutex_lock(&shared.mutex);
        item=i;
        item=shared.buf[shared.out];
        shared.out = (shared.out+1)%BUFF_SIZE;
        printf("[C%d] Consuming  %d ...\n", index, item);
        fflush(stdout);
        /* Release the buffer */
        pthread_mutex_unlock(&shared.mutex);
        /* Increment the number of full slots */
        sem_post(&shared.empty);

        /* Interleave  producer and consumer execution */
        if (i % 2 == 1) sleep(1);
    }
    return NULL;
}

int main()
{
    pthread_t idP, idC;
    int index;

    sem_init(&shared.full, 0, 0);
    sem_init(&shared.empty, 0, BUFF_SIZE);
    pthread_mutex_init(&shared.mutex, NULL);
    for (index = 0; index < NP; index++)
    {
        /* Create a new producer */
        pthread_create(&idP, NULL, Producer, (void*)index);
    }
    /*create a new Consumer*/
    for(index=0; index<NC; index++)
    {
        pthread_create(&idC, NULL, Consumer, (void*)index);
    }



    pthread_exit(NULL);
}
producer/consumer using Pthreads and Semaphores

producer/consumer using Pthreads and Semaphores


By : Krishna Priya
Date : March 29 2020, 07:55 AM
around this issue 1) The = operator on a string copies by value. The following code is copying by value into the 'buffer' variable. However, later you are using p1_string in an infinite loop expecting it to update. Assigning a new value to the pthread_param.buffer does not change the value of px_string. Thus, in this case the strings will always equal their initial value and string 1 will always be less than string 2.
code :
pt1_param.buffer = p1_string; //assignment by value
pt2_param.buffer = p2_string; //assignment by value
while (1)
{
    sem_wait()
    if (!getline(buffer))
        break;
    sem_post()
}
Logic error in my defined Mutex class and the way I use it in producer consumer program - pthreads

Logic error in my defined Mutex class and the way I use it in producer consumer program - pthreads


By : Felipe Morselli
Date : March 29 2020, 07:55 AM
hop of those help? Currently, you initialize mutexVariable to PTHREAD_MUTEX_INITIALIZER every time you create a new construct a new MutexClass. Consider what happens if thread A holds the mutexVariable and thread B wants to acquire the mutex:
code :
thread A tries to lock mutexVariable and succeeds
    mutexVariable = PTHRAED_MUTEX_INITIALIZER
    pthread_mutex_lock(mutexVariable)

thread B tries to lock mutexVariable and succeeds
    // this assignment overwrites the locked state thread A has stored
    mutexVariable = PTHRAED_MUTEX_INITIALIZER
    // mutex is default-initialized (not locked) - so lock it
    pthread_mutex_lock(mutexVariable)
    // both threads now believe they have the mutex
    // and all syncronization is lost

thread B unlocks mutexVariable
    // succeeds

thread A unlocks mutexVariable
    // uh.. it is not even locked any more?!
pthread_mutex_t mutexVariable = PTHRAED_MUTEX_INITIALIZER;
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