1 /* Copyright (c) 2013-2022. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #include "../colls_private.hpp"
8 /*****************************************************************************
10 * Function: alltoall_ring
15 send_buff: send input buffer
16 send_count: number of elements to send
17 send_type: data type of elements being sent
18 recv_buff: receive output buffer
19 recv_count: number of elements to received
20 recv_type: data type of elements being received
23 * Descrp: Function works in P - 1 steps. In step i, node j - i -> j -> j + i.
27 ****************************************************************************/
30 int alltoall__ring(const void *send_buff, int send_count,
31 MPI_Datatype send_type, void *recv_buff,
32 int recv_count, MPI_Datatype recv_type,
36 MPI_Aint send_chunk, recv_chunk;
37 int i, src, dst, rank, num_procs;
38 int tag = COLL_TAG_ALLTOALL;
40 char *send_ptr = (char *) send_buff;
41 char *recv_ptr = (char *) recv_buff;
44 num_procs = comm->size();
45 send_chunk = send_type->get_extent();
46 recv_chunk = recv_type->get_extent();
48 send_chunk *= send_count;
49 recv_chunk *= recv_count;
51 for (i = 0; i < num_procs; i++) {
52 src = (rank - i + num_procs) % num_procs;
53 dst = (rank + i) % num_procs;
55 Request::sendrecv(send_ptr + dst * send_chunk, send_count, send_type, dst,
56 tag, recv_ptr + src * recv_chunk, recv_count, recv_type,