73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
/*
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* pthreads4.c - Shows how to pass parameter values to thread routines
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* The threads dereference the pointer passed to the
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* thread routine to demonstrate that memory is shared
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* between all threads
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*/
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#include <pthread.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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// Function to check if a number is prime
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// Returns 1 if prime, 0 if not prime
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int is_prime(int v)
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{
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for(int i = 2; i < v; i++) {
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if(v % i == 0) {
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return 0;
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}
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}
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return 1;
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}
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// Thread routine
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// calls is_prime to check if the input argument is prime
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// Modifies the input parameter by dereferencing the pointer
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//
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// NOTE: that parameters and return value are pointers
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void* thread_routine(void* args)
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{
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int* val = (int*)args;
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if(is_prime(*val)) {
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printf("THREAD %lu FOUND that %d is prime\n", pthread_self(), *val);
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*val = 1;
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} else {
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printf("THREAD %lu FOUND that %d is not prime\n", pthread_self(), *val);
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*val = 0;
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}
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return NULL;
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}
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int main()
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{
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int val1 = 2;
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int val2 = 100;
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// Print out the values before creating threads
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printf("Parent val1=%d val2=%d\n", val1, val2);
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// Create 2 threads
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pthread_t thr1;
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pthread_t thr2;
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if(pthread_create(&thr1, NULL, thread_routine, (void*)&val1) == -1) {
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printf("COULD NOT CREATE A THREAD\n");
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exit(EXIT_FAILURE);
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}
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if(pthread_create(&thr2, NULL, thread_routine, (void*)&val2) == -1) {
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printf("COULD NOT CREATE A THREAD\n");
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exit(EXIT_FAILURE);
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}
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// Wait for the threads to finish
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pthread_join(thr1, NULL);
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pthread_join(thr2, NULL);
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// Print out the final values
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printf("Parent val1=%d val2=%d\n", val1, val2);
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// Return success
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return 0;
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}
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