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51 lines
1.3 KiB
C
51 lines
1.3 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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#include <math.h>
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#include <mpi.h>
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int main(int argc, char *argv[]) {
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if(argc != 2) {
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fprintf(stderr, "Uso: %s <tiros>\n", argv[0]);
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return 1;
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}
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int mi_rank, num_procs;
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MPI_Init(&argc, &argv);
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MPI_Comm_size(MPI_COMM_WORLD, &num_procs);
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MPI_Comm_rank(MPI_COMM_WORLD, &mi_rank);
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if(! mi_rank)
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printf("Procesos: %d\n", num_procs);
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srand(time(NULL) + mi_rank); // Ojo, tal vez un proceso se lanza un segundo después que otro y esta cuenta coincide.
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size_t tiros = atol(argv[1]);
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tiros = tiros / num_procs * num_procs;
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size_t positivos_parciales = 0;
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for(size_t i = 0; i < tiros / num_procs; i++) {
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double x = (double)random() / RAND_MAX;
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double y = (double)random() / RAND_MAX;
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if(x * x + y * y < 1)
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positivos_parciales++;
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}
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size_t positivos;
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MPI_Reduce(&positivos_parciales, &positivos, 1, MPI_LONG, MPI_SUM, 0, MPI_COMM_WORLD);
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if(! mi_rank) {
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double pi = 4.0 * positivos / tiros;
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printf("Tiros = %zd, Positivos = %zd\n", tiros, positivos);
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printf("π ~= %.15f\n", pi);
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printf("ε = %f%%\n", 100 * fabs(M_PI - pi) / M_PI);
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}
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MPI_Finalize();
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return 0;
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}
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