1 /* Copyright (c) 2013-2023. 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 ****************************************************************************/
28 namespace simgrid::smpi {
29 int alltoallv__ring(const void* send_buff, const int* send_counts, const int* send_disps, MPI_Datatype send_type,
30 void* recv_buff, const int* recv_counts, const int* recv_disps, MPI_Datatype recv_type,
34 MPI_Aint send_chunk, recv_chunk;
35 int i, src, dst, rank, num_procs;
36 int tag = COLL_TAG_ALLTOALLV;
38 char *send_ptr = (char *) send_buff;
39 char *recv_ptr = (char *) recv_buff;
42 num_procs = comm->size();
43 send_chunk = send_type->get_extent();
44 recv_chunk = recv_type->get_extent();
45 bool pof2 = ((num_procs != 0) && ((num_procs & (~num_procs + 1)) == num_procs));
46 for (i = 0; i < num_procs; i++) {
49 /* use exclusive-or algorithm */
52 src = (rank - i + num_procs) % num_procs;
53 dst = (rank + i) % num_procs;
56 Request::sendrecv(send_ptr + send_disps[dst] * send_chunk, send_counts[dst], send_type, dst,
57 tag, recv_ptr + recv_disps[src] * recv_chunk, recv_counts[src], recv_type,
63 } // namespace simgrid::smpi