103 lines
2.4 KiB
C
103 lines
2.4 KiB
C
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#include <stdio.h>
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#include <pthread.h>
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#include <omp.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <math.h>
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#define N_THREADS 8
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#define N_DIMENSIONS 200000000
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pthread_barrier_t b;
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long *p_s;
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long *q_s;
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double res[N_THREADS];
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int active_threads[N_THREADS];
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void setup() {
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p_s = (long *) malloc(N_DIMENSIONS * sizeof(long));
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q_s = (long *) malloc(N_DIMENSIONS * sizeof(long));
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for (long i = 0; i < N_DIMENSIONS; i++) {
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p_s[i] = rand() % 10;
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q_s[i] = rand() % 10;
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}
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}
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void *calculate(void* arg) {
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int *myrank = (int *)arg;
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long mystart = (long)(N_DIMENSIONS/ (double)N_THREADS * *myrank);
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long myend = (long)(N_DIMENSIONS / (double)N_THREADS * (*myrank + 1));
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double sum = 0;
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for (long i = mystart; i < myend; i++) {
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sum += pow(p_s[i] - q_s[i], 2);
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}
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res[*myrank] = sum;
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printf("Thread2 %d finished\n", *myrank);
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fflush(stdout);
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pthread_barrier_wait( &b );
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int n_threads = N_THREADS;
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if (n_threads != 1) {
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n_threads = N_THREADS / 2;
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if (*myrank >= n_threads) {
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active_threads[*myrank] = -1;
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}
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}
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while(1) {
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if(active_threads[*myrank] != -1) {
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res[*myrank] = res[*myrank * 2] + res[*myrank *2 + 1];
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}
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pthread_barrier_wait( &b );
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n_threads = n_threads / 2;
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if (n_threads == 1 || n_threads == 0) {
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break;
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}
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if (*myrank >= n_threads) {
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//printf("Thread %d is on pause\n", *myrank);
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active_threads[*myrank] = -1;
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}
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pthread_barrier_wait( &b );
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}
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return NULL;
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}
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int main() {
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pthread_t t[N_THREADS];
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setup();
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double dt = omp_get_wtime(); // start timing
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int p[N_THREADS];
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if(N_THREADS %2 != 0 && N_THREADS >= 2) {
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printf("Number of threads must be even!\n");
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return 1;
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}
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pthread_barrier_init( &b, NULL, N_THREADS );
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for(int i = 0; i < N_THREADS; i++ ) {
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p[i] = i;
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pthread_create(&t[i], NULL, calculate, (void *)&p[i]);
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}
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for(int i=0; i<N_THREADS; i++)
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pthread_join(t[i], NULL);
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dt = omp_get_wtime() - dt; // finish timing
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printf("Execution time: %lf, caluclation result: %lf ", dt, sqrt(res[0]));
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return 0;
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// 8 THREADS: Execution time: 0.807376, caluclation result: 49748.358094
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// 4 THREADS: Execution time: 1.614672, caluclation result: 49748.358094
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// 2 THREADS: Execution time: 3.223820, caluclation result: 57445.749660
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// 1 THREADS: Execution time: 4.698835, caluclation result: 57445.749660
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}
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