86 lines
2.8 KiB
C
86 lines
2.8 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <mpi.h>
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int main(int argc, char *argv[])
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{
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int size;
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int my_rank;
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int data_size = -100;
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int *buffer_send, *buffer_recv;
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int tag;
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MPI_Status status;
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int l;
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char name[MPI_MAX_PROCESSOR_NAME];
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// Make sure that the command line has one argument (the size of the data)
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if (argc != 2)
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{
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printf("usage : limite <data size>\n");
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return EXIT_FAILURE;
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}
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MPI_Init(&argc, &argv);
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// Make sure exactly 2 MPI processes are used
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MPI_Comm_size(MPI_COMM_WORLD, &size);
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if (size != 2)
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{
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printf("%d MPI processes used, please use 2.\n", size);
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MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
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}
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MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
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MPI_Get_processor_name(name, &l);
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printf("process %d of %d on processor named %s\n", my_rank, size, name);
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// Prepare parameters
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data_size = atoi(argv[1]);
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printf("The size of the data is %d\n", data_size);
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buffer_send = (int *)malloc(data_size * sizeof(int));
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buffer_recv = (int *)malloc(data_size * sizeof(int));
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buffer_send[0] = (my_rank == 0) ? 12345 : 67890;
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tag = 0;
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if (my_rank == 0)
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{
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// node 0 sends its buffer buffer_send of size data_size to node 1
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MPI_Send(buffer_send, data_size, MPI_INT, 1, tag, MPI_COMM_WORLD);
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// node 0 receives in its buffer buffer_recv data from node 1
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MPI_Recv(buffer_recv, data_size, MPI_INT, 1, tag, MPI_COMM_WORLD, &status);
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printf("MPI process %d received value %d from MPI process %d.\n", my_rank, buffer_recv[0], 1);
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}
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else
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{
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// node 1 sends its buffer buffer_send of size data_size to node 0
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MPI_Send(buffer_send, data_size, MPI_INT, 0, tag, MPI_COMM_WORLD);
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// node 1 receives in its buffer buffer_recv data from node 0
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MPI_Recv(buffer_recv, data_size, MPI_INT, 0, tag, MPI_COMM_WORLD, &status);
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printf("MPI process %d received value %d from MPI process %d.\n", my_rank, buffer_recv[0], 0);
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}
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free(buffer_send);
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free(buffer_recv);
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MPI_Finalize();
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return EXIT_SUCCESS;
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}
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// (a) rappelez pour quelle taille de message (petite, grande), MPI Send aura un comportement asynchrone (resp. synchrone)
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// ->
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// (b) que va-t-il se passer quand votre programme, compl ́et ́e comme indiqu ́e, sera appel ́e avec une taille de message qui fera que MPI Send sera synchrone ?
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// -> deadlock, on passe en synchrone
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// (c) estimez `a 10 entiers pr`es, la taille limite sur deux noeuds du mˆeme ordinateur ?
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// -> 16383
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// (d) proposez une solution pour que l’ ́echange entre les deux noeuds puissent se faire au del`a de cette limite (plusieurs r ́eponses possibles). Vous avez la possibilit ́e de les tester en dehors de la s ́eance.
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// -> découper le buffer de telle manière à n'envoyer que des petits buffers en asynchrone
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// -> changer ordre send/recv du deuxième noeud
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