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/* Copyright (c) 2013-2025. The SimGrid Team. All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
* under the terms of the license (GNU LGPL) which comes with this package. */
#include "../colls_private.hpp"
/*****************************************************************************
* Function: alltoall_ring
* Return: int
* Inputs:
send_buff: send input buffer
send_count: number of elements to send
send_type: data type of elements being sent
recv_buff: receive output buffer
recv_count: number of elements to received
recv_type: data type of elements being received
comm: communicator
* Descrp: Function works in P - 1 steps. In step i, node j - i -> j -> j + i.
* Author: Ahmad Faraj
****************************************************************************/
namespace simgrid::smpi {
int alltoall__ring(const void *send_buff, int send_count,
MPI_Datatype send_type, void *recv_buff,
int recv_count, MPI_Datatype recv_type,
MPI_Comm comm)
{
MPI_Status s;
MPI_Aint send_chunk, recv_chunk;
int i, src, dst, rank, num_procs;
int tag = COLL_TAG_ALLTOALL;
char *send_ptr = (char *) send_buff;
char *recv_ptr = (char *) recv_buff;
rank = comm->rank();
num_procs = comm->size();
send_chunk = send_type->get_extent();
recv_chunk = recv_type->get_extent();
send_chunk *= send_count;
recv_chunk *= recv_count;
for (i = 0; i < num_procs; i++) {
src = (rank - i + num_procs) % num_procs;
dst = (rank + i) % num_procs;
Request::sendrecv(send_ptr + dst * send_chunk, send_count, send_type, dst,
tag, recv_ptr + src * recv_chunk, recv_count, recv_type,
src, tag, comm, &s);
}
return MPI_SUCCESS;
}
} // namespace simgrid::smpi
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