test_atomic.cpp revision 12751 
1/*
2  * Copyright (c) 2018, Cornell University
3  * All rights reserved.
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11  *
12  * Redistributions in binary form must reproduce the above
13  * copyright notice, this list of conditions and the following
14  * disclaimer in the documentation and/or other materials provided
15  * with the distribution.
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18  * contributors may be used to endorse or promote products derived
19  * from this software without specific prior written permission.
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21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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24  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
25  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
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29  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
30  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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34  *
35  * Authors: Tuan Ta
36  */
37
38#include <pthread.h>
39
40#include <atomic>
41#include <cstdlib>
42#include <iostream>
43
44//------------------------------------------------------------------------
45// Create n threads, run them in parallel and wait for them in the master
46// thread.
47// Each child thread increments a shared variable m times atomically
48//------------------------------------------------------------------------
49
50#define MAX_N_WORKER_THREADS 10
51
52typedef struct
53{
54    int nsteps;
55    std::atomic<int>* shared_var;
56} ThreadArg;
57
58void* func( void* args )
59{
60    ThreadArg* my_args = ( ThreadArg* ) args;
61
62    int nsteps = my_args->nsteps;
63    std::atomic<int>* shared_var = my_args->shared_var;
64
65    for ( int i = 0; i < nsteps; ++i ) {
66        std::atomic_fetch_add(shared_var, 1);
67    }
68
69    return nullptr;
70}
71
72int main( int argc, const char* argv[] )
73{
74    int n_worker_threads = 0;
75
76    // allocate all threads
77    pthread_t* threads = new pthread_t[MAX_N_WORKER_THREADS];
78
79    // variable shared among all threads
80    std::atomic<int> shared_var(0);
81
82    // number of steps each thread increments the shared_var
83    int nsteps = 1000;
84
85    // set up threads' arguments
86    ThreadArg* t_args = new ThreadArg[MAX_N_WORKER_THREADS];
87
88    int ret = 0;
89    for ( size_t tid = 0; tid < MAX_N_WORKER_THREADS; tid++ ){
90        t_args[tid].nsteps = nsteps;
91        t_args[tid].shared_var = &shared_var;
92
93        // spawn thread
94        ret = pthread_create( threads + tid, nullptr, func, &t_args[tid] );
95
96        if (ret != 0) {
97            break;
98        }
99
100        n_worker_threads++;
101    }
102
103    // sync up all threads
104    for ( int tid = 0; tid < n_worker_threads; ++tid ) {
105        pthread_join( threads[tid], nullptr );
106    }
107
108    // clean up
109    delete[] threads;
110    delete[] t_args;
111
112    // verify
113    if ( shared_var != n_worker_threads * nsteps || n_worker_threads < 1)
114        return EXIT_FAILURE;
115
116    return EXIT_SUCCESS;
117}
118