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"
10 /*****************************************************************************
12 * Function: alltoall_2dmesh_shoot
17 send_buff: send input buffer
18 send_count: number of elements to send
19 send_type: data type of elements being sent
20 recv_buff: receive output buffer
21 recv_count: number of elements to received
22 recv_type: data type of elements being received
25 * Descrp: Function realizes the alltoall operation using the 2dmesh
26 algorithm. It actually performs allgather operation in x dimension
27 then in the y dimension. Each node then extracts the needed data.
28 The communication in each dimension follows "simple."
32 ****************************************************************************/
33 static int alltoall_check_is_2dmesh(int num, int *i, int *j)
36 x = sqrt(double(num));
55 namespace simgrid::smpi {
57 int alltoall__2dmesh(const void *send_buff, int send_count,
58 MPI_Datatype send_type,
59 void *recv_buff, int recv_count,
60 MPI_Datatype recv_type, MPI_Comm comm)
65 int i, j, src, dst, rank, num_procs, count, num_reqs;
66 int X, Y, send_offset, recv_offset;
67 int my_row_base, my_col_base, src_row_base, block_size;
68 int tag = COLL_TAG_ALLTOALL;
71 num_procs = comm->size();
72 extent = send_type->get_extent();
74 if (not alltoall_check_is_2dmesh(num_procs, &X, &Y))
77 my_row_base = (rank / Y) * Y;
78 my_col_base = rank % Y;
80 block_size = extent * send_count;
82 unsigned char* tmp_buff1 = smpi_get_tmp_sendbuffer(block_size * num_procs * Y);
83 unsigned char* tmp_buff2 = smpi_get_tmp_recvbuffer(block_size * Y);
89 auto* statuses = new MPI_Status[num_reqs];
90 auto* reqs = new MPI_Request[num_reqs];
91 MPI_Request* req_ptr = reqs;
93 count = send_count * num_procs;
95 for (i = 0; i < Y; i++) {
96 src = i + my_row_base;
100 recv_offset = (src % Y) * block_size * num_procs;
101 *(req_ptr++) = Request::irecv(tmp_buff1 + recv_offset, count, recv_type, src, tag, comm);
104 for (i = 0; i < Y; i++) {
105 dst = i + my_row_base;
108 Request::send(send_buff, count, send_type, dst, tag, comm);
111 Request::waitall(Y - 1, reqs, statuses);
114 for (i = 0; i < Y; i++) {
115 send_offset = (rank * block_size) + (i * block_size * num_procs);
116 recv_offset = (my_row_base * block_size) + (i * block_size);
118 if (i + my_row_base == rank)
119 Request::sendrecv((char *) send_buff + recv_offset, send_count, send_type,
121 (char *) recv_buff + recv_offset, recv_count, recv_type,
122 rank, tag, comm, &s);
125 Request::sendrecv(tmp_buff1 + send_offset, send_count, send_type,
127 (char *) recv_buff + recv_offset, recv_count, recv_type,
128 rank, tag, comm, &s);
132 for (i = 0; i < X; i++) {
133 src = (i * Y + my_col_base);
136 src_row_base = (src / Y) * Y;
138 *(req_ptr++) = Request::irecv((char *) recv_buff + src_row_base * block_size, recv_count * Y,
139 recv_type, src, tag, comm);
142 for (i = 0; i < X; i++) {
143 dst = (i * Y + my_col_base);
148 for (j = 0; j < Y; j++) {
149 send_offset = (dst + j * num_procs) * block_size;
151 if (j + my_row_base == rank)
152 Request::sendrecv((char *) send_buff + dst * block_size, send_count,
153 send_type, rank, tag, tmp_buff2 + recv_offset, recv_count,
154 recv_type, rank, tag, comm, &s);
156 Request::sendrecv(tmp_buff1 + send_offset, send_count, send_type,
158 tmp_buff2 + recv_offset, recv_count, recv_type,
159 rank, tag, comm, &s);
161 recv_offset += block_size;
164 Request::send(tmp_buff2, send_count * Y, send_type, dst, tag, comm);
166 Request::waitall(X - 1, reqs, statuses);
169 smpi_free_tmp_buffer(tmp_buff1);
170 smpi_free_tmp_buffer(tmp_buff2);
173 } // namespace simgrid::smpi