49 lines
1.1 KiB
C
49 lines
1.1 KiB
C
#include <pthread.h>
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#include <inttypes.h>
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#include <assert.h>
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#include <stdio.h>
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#include <stdatomic.h>
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#define RUNS (4096 * 256)
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#define THREADS 4
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static int leader[RUNS] = { 0 };
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static atomic_int nb_leaders[RUNS] = { 0 }; // used to check correctness
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void* elect(void* _tid) {
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intptr_t tid = (intptr_t) _tid;
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// For each run (or round) we try to impose ourselves as the run's leader.
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for (int r = 0; r < RUNS; r++) {
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if (leader[r] == 0) {
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leader[r] = tid;
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atomic_fetch_add(&nb_leaders[r], 1); // used to check correctness
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}
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// **Incorrect**, super wrong, plz synchronize.
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}
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}
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int main() {
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pthread_t handlers[THREADS];
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for (intptr_t i = 0; i < THREADS; i++) {
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int res = pthread_create(&handlers[i], NULL, elect, (void*)(i + 1));
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assert(!res);
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}
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for (int i = 0; i < THREADS; i++) {
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int res = pthread_join(handlers[i], NULL);
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assert(!res);
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}
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int r = 0;
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for (; r < RUNS; r++) {
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if (nb_leaders[r] != 1) {
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printf("Leader election for round %d failed.\n", r);
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break;
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}
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}
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if (r == RUNS) {
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printf("Looks correct to me! :)\n");
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}
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}
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