2 /*****************************************************************************
4 * Function: alltoall_ring
9 send_buff: send input buffer
10 send_count: number of elements to send
11 send_type: data type of elements being sent
12 recv_buff: receive output buffer
13 recv_count: number of elements to received
14 recv_type: data type of elements being received
17 * Descrp: Function works in P - 1 steps. In step i, node j - i -> j -> j + i.
21 ****************************************************************************/
23 smpi_coll_tuned_alltoall_ring(void *send_buff, int send_count,
24 MPI_Datatype send_type, void *recv_buff,
25 int recv_count, MPI_Datatype recv_type,
29 MPI_Aint send_chunk, recv_chunk;
30 int i, src, dst, rank, num_procs;
31 int tag = 1, success = 1; /*, failure = 0, pof2 = 1 */ ;
33 char *send_ptr = (char *) send_buff;
34 char *recv_ptr = (char *) recv_buff;
36 MPI_Comm_rank(comm, &rank);
37 MPI_Comm_size(comm, &num_procs);
38 MPI_Type_extent(send_type, &send_chunk);
39 MPI_Type_extent(recv_type, &recv_chunk);
41 send_chunk *= send_count;
42 recv_chunk *= recv_count;
44 for (i = 0; i < num_procs; i++) {
45 src = (rank - i + num_procs) % num_procs;
46 dst = (rank + i) % num_procs;
48 MPI_Sendrecv(send_ptr + dst * send_chunk, send_count, send_type, dst,
49 tag, recv_ptr + src * recv_chunk, recv_count, recv_type,