src/simple/pthread_create_para.cpp

/*
  * Copyright (c) 2018, Cornell University
  * All rights reserved.
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  * notice, this list of conditions and the following disclaimer.
  *
  * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following
  * disclaimer in the documentation and/or other materials provided
  * with the distribution.
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  * Neither the name of Cornell University nor the names of its
  * contributors may be used to endorse or promote products derived
  * from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
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  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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#include <pthread.h>

#include <cstdlib>
#include <iostream>

//------------------------------------------------------------------------
// Create n threads, run them in parallel and wait for them in the master
// thread.
// Each child thread writes its thread id to an output array
//------------------------------------------------------------------------

#define MAX_N_WORKER_THREADS 10

typedef struct
{
    int tid;
    int* output;
} ThreadArg;

void* func( void* args )
{
    ThreadArg* my_args = ( ThreadArg* ) args;

    // write tid to this thread's output
    (*my_args->output) = my_args->tid;

    return nullptr;
}

int main()
{
    int n_worker_threads = 0;

    // allocate all threads
    pthread_t* threads = new pthread_t[MAX_N_WORKER_THREADS];
    ThreadArg* t_args = new ThreadArg[MAX_N_WORKER_THREADS];

    // create an output array for all threads
    int* outputs = new int[MAX_N_WORKER_THREADS];
    int ret;

    // try to spawn as many worker threads as possible
    for ( int tid = 0; tid < MAX_N_WORKER_THREADS; ++tid ) {

        // set up thread args
        t_args[tid].tid = tid;
        t_args[tid].output = outputs + tid;

        // spawn thread
        ret = pthread_create( threads + tid, nullptr, func, &t_args[tid] );
        if (ret != 0) {
            break;
        }

        n_worker_threads++;
    }

    // sync up all threads
    for ( int tid = 0; tid < n_worker_threads; ++tid ) {
        pthread_join( threads[tid], nullptr );
    }

    // verify
    bool passed = true;
    for ( int i = 0; i < n_worker_threads; ++i ) {
        if ( outputs[i] != i ) {
            passed = false;
        }
    }

    // clean up
    delete[] threads;
    delete[] t_args;
    delete[] outputs;

    // failed if outputs are not correct or no worker thread was spawned
    if (!passed || n_worker_threads < 1)
        return EXIT_FAILURE;

    return EXIT_SUCCESS;
}