91 lines
1.8 KiB
C
91 lines
1.8 KiB
C
#include <limits.h>
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#include <pthread.h>
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#include "suma.h"
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enum { NTHREADS = 8 };
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typedef struct {
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int *a;
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int n;
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Set start;
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Set end;
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Set found;
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} BuscarArgs;
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static Set total_combinaciones(int n) {
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if (n >= (int)(sizeof(Set) * CHAR_BIT))
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return ~(Set)0;
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return ((Set)1 << n) - 1;
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}
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static Set buscar_rango(int a[], int n, Set start, Set end) {
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if (start == 0 || start > end)
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return 0;
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Set k = start;
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while (1) {
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long long sum = 0;
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for (int i = 0; i < n; i++) {
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if (k & ((Set)1 << i))
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sum += a[i];
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}
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if (sum == 0)
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return k;
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if (k == end)
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break;
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k++;
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}
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return 0;
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}
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static void *buscar_thread(void *ptr) {
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BuscarArgs *args = ptr;
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args->found = buscar_rango(args->a, args->n, args->start, args->end);
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return NULL;
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}
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Set buscar(int a[], int n) {
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Set comb = total_combinaciones(n);
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Set base = comb / NTHREADS;
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Set extra = comb % NTHREADS;
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Set next = 1;
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pthread_t tids[NTHREADS];
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BuscarArgs args[NTHREADS];
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int created = 0;
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for (int t = 0; t < NTHREADS; t++) {
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Set len = base + (Set)(t < (int)extra);
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args[t].a = a;
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args[t].n = n;
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args[t].start = next;
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args[t].end = (len == 0) ? next - 1
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: (t == NTHREADS - 1 ? comb : next + len - 1);
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args[t].found = 0;
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if (len != 0)
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next = args[t].end + 1;
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if (pthread_create(&tids[t], NULL, buscar_thread, &args[t]) != 0) {
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for (int i = 0; i < created; i++)
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pthread_join(tids[i], NULL);
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return buscar_rango(a, n, 1, comb);
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}
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created++;
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}
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Set best = 0;
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for (int t = 0; t < NTHREADS; t++) {
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pthread_join(tids[t], NULL);
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if (args[t].found != 0 && (best == 0 || args[t].found < best))
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best = args[t].found;
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}
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return best;
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}
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