X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/9099504f0b246a1031adb644ac0835d526a33ffd..e5ffbd7cb554dd3678545d575126a1a97d6c57c9:/docs/source/tuto_smpi/roundtrip.c

diff --git a/docs/source/tuto_smpi/roundtrip.c b/docs/source/tuto_smpi/roundtrip.c
new file mode 100644
index 0000000000..53f523b482
--- /dev/null
+++ b/docs/source/tuto_smpi/roundtrip.c
@@ -0,0 +1,42 @@
+#include <mpi.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define N (1024 * 1024 * 1)
+
+int main(int argc, char* argv[])
+{
+  int size, rank;
+  struct timeval start, end;
+  char hostname[256];
+  int hostname_len;
+
+  MPI_Init(&argc, &argv);
+
+  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
+  MPI_Comm_size(MPI_COMM_WORLD, &size);
+  MPI_Get_processor_name(hostname, &hostname_len);
+
+  // Allocate a 1 MiB buffer
+  char* buffer = malloc(sizeof(char) * N);
+
+  // Communicate along the ring
+  if (rank == 0) {
+    gettimeofday(&start, NULL);
+    printf("Rank %d (running on '%s'): sending the message rank %d\n", rank, hostname, 1);
+    MPI_Send(buffer, N, MPI_BYTE, 1, 1, MPI_COMM_WORLD);
+    MPI_Recv(buffer, N, MPI_BYTE, size - 1, 1, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
+    printf("Rank %d (running on '%s'): received the message from rank %d\n", rank, hostname, size - 1);
+    gettimeofday(&end, NULL);
+    printf("%f\n", (end.tv_sec * 1000000.0 + end.tv_usec - start.tv_sec * 1000000.0 - start.tv_usec) / 1000000.0);
+
+  } else {
+    MPI_Recv(buffer, N, MPI_BYTE, rank - 1, 1, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
+    printf("Rank %d (running on '%s'): receive the message and sending it to rank %d\n", rank, hostname,
+           (rank + 1) % size);
+    MPI_Send(buffer, N, MPI_BYTE, (rank + 1) % size, 1, MPI_COMM_WORLD);
+  }
+
+  MPI_Finalize();
+  return 0;
+}