3 /*****************************************************************************
5 * Function: alltoall_spreading_simple
10 send_buff: send input buffer
11 send_count: number of elements to send
12 send_type: data type of elements being sent
13 recv_buff: receive output buffer
14 recv_count: number of elements to received
15 recv_type: data type of elements being received
18 * Descrp: Let i -> j denote the communication from node i to node j. The
19 order of communications for node i is i -> i + 1, i -> i + 2, ...,
24 ****************************************************************************/
26 smpi_coll_tuned_alltoall_simple(void * send_buff, int send_count,
27 MPI_Datatype send_type, void * recv_buff,
28 int recv_count, MPI_Datatype recv_type,
31 int i, rank, size, nreqs, err, src, dst, tag = 101;
39 MPI_Status s, * statuses;
42 MPI_Comm_size(comm, &size);
43 MPI_Comm_rank(comm, &rank);
44 MPI_Type_extent(send_type, &sndinc);
45 MPI_Type_extent(recv_type, &rcvinc);
49 /* Allocate arrays of requests. */
51 nreqs = 2 * (size - 1);
54 req = (MPI_Request *) malloc(nreqs * sizeof(MPI_Request));
55 statuses = (MPI_Status *) malloc(nreqs * sizeof(MPI_Status));
56 if (!req || !statuses)
66 /* simple optimization */
68 psnd = ((char *) send_buff) + (rank * sndinc);
69 prcv = ((char *) recv_buff) + (rank * rcvinc);
70 MPI_Sendrecv (psnd, send_count, send_type, rank, tag,
71 prcv, recv_count, recv_type,
75 /* Initiate all send/recv to/from others. */
78 qreq = req + size - 1;
79 prcv = (char*) recv_buff;
80 psnd = (char*) send_buff;
81 for (i = 0; i < size; i++)
83 src = dst = (rank + i) % size;
84 if (src == rank) continue;
85 if (dst == rank) continue;
86 MPI_Recv_init(prcv + (src * rcvinc), recv_count, recv_type, src,
88 MPI_Send_init(psnd + (dst * sndinc), send_count, send_type, dst,
92 /* Start all the requests. */
94 err = MPI_Startall(nreqs, req);
96 /* Wait for them all. */
98 err = MPI_Waitall(nreqs, req, statuses);
100 if (err != MPI_SUCCESS) {
106 for (i = 0, preq = req; i < nreqs; ++i, ++preq) {
107 err = MPI_Request_free(preq);
108 if (err != MPI_SUCCESS) {