/* Copyright (c) 2013-2018. 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"
/* IMPLEMENTED BY PITCH PATARASUK
   Non-topoloty-specific (however, number of cores/node need to be changed)
   all-reduce operation designed for smp clusters
   It uses 2-layer communication: binomial for both intra-communication
   inter-communication*/


/* ** NOTE **
   Use -DMPICH2 if this code does not compile.
   MPICH1 code also work on MPICH2 on our cluster and the performance are similar.
   This code assume commutative and associative reduce operator (MPI_SUM, MPI_MAX, etc).
*/

//#include <star-reduction.c>

/*
This fucntion performs all-reduce operation as follow.
1) binomial_tree reduce inside each SMP node
2) binomial_tree reduce intra-communication between root of each SMP node
3) binomial_tree bcast intra-communication between root of each SMP node
4) binomial_tree bcast inside each SMP node
*/
namespace simgrid{
namespace smpi{
int Coll_allreduce_smp_binomial::allreduce(void *send_buf, void *recv_buf,
                                           int count, MPI_Datatype dtype,
                                           MPI_Op op, MPI_Comm comm)
{
  int comm_size, rank;
  void *tmp_buf;
  int tag = COLL_TAG_ALLREDUCE;
  int mask, src, dst;

  if(comm->get_leaders_comm()==MPI_COMM_NULL){
    comm->init_smp();
  }
  int num_core=1;
  if (comm->is_uniform()){
    num_core = comm->get_intra_comm()->size();
  }
  MPI_Status status;

  comm_size=comm->size();
  rank=comm->rank();
  MPI_Aint extent, lb;
  dtype->extent(&lb, &extent);
  tmp_buf = (void *) smpi_get_tmp_sendbuffer(count * extent);

  /* compute intra and inter ranking */
  int intra_rank, inter_rank;
  intra_rank = rank % num_core;
  inter_rank = rank / num_core;

  /* size of processes participate in intra communications =>
     should be equal to number of machines */
  int inter_comm_size = (comm_size + num_core - 1) / num_core;

  /* copy input buffer to output buffer */
  Request::sendrecv(send_buf, count, dtype, rank, tag,
               recv_buf, count, dtype, rank, tag, comm, &status);

  /* start binomial reduce intra communication inside each SMP node */
  mask = 1;
  while (mask < num_core) {
    if ((mask & intra_rank) == 0) {
      src = (inter_rank * num_core) + (intra_rank | mask);
      if (src < comm_size) {
        Request::recv(tmp_buf, count, dtype, src, tag, comm, &status);
        if(op!=MPI_OP_NULL) op->apply( tmp_buf, recv_buf, &count, dtype);
      }
    } else {
      dst = (inter_rank * num_core) + (intra_rank & (~mask));
      Request::send(recv_buf, count, dtype, dst, tag, comm);
      break;
    }
    mask <<= 1;
  }

  /* start binomial reduce inter-communication between each SMP nodes:
     each node only have one process that can communicate to other nodes */
  if (intra_rank == 0) {
    mask = 1;
    while (mask < inter_comm_size) {
      if ((mask & inter_rank) == 0) {
        src = (inter_rank | mask) * num_core;
        if (src < comm_size) {
          Request::recv(tmp_buf, count, dtype, src, tag, comm, &status);
          if(op!=MPI_OP_NULL) op->apply( tmp_buf, recv_buf, &count, dtype);
        }
      } else {
        dst = (inter_rank & (~mask)) * num_core;
        Request::send(recv_buf, count, dtype, dst, tag, comm);
        break;
      }
      mask <<= 1;
    }
  }

  /* start binomial broadcast inter-communication between each SMP nodes:
     each node only have one process that can communicate to other nodes */
  if (intra_rank == 0) {
    mask = 1;
    while (mask < inter_comm_size) {
      if (inter_rank & mask) {
        src = (inter_rank - mask) * num_core;
        Request::recv(recv_buf, count, dtype, src, tag, comm, &status);
        break;
      }
      mask <<= 1;
    }
    mask >>= 1;

    while (mask > 0) {
      if (inter_rank < inter_comm_size) {
        dst = (inter_rank + mask) * num_core;
        if (dst < comm_size) {
          Request::send(recv_buf, count, dtype, dst, tag, comm);
        }
      }
      mask >>= 1;
    }
  }

  /* start binomial broadcast intra-communication inside each SMP nodes */
  int num_core_in_current_smp = num_core;
  if (inter_rank == (inter_comm_size - 1)) {
    num_core_in_current_smp = comm_size - (inter_rank * num_core);
  }
  mask = 1;
  while (mask < num_core_in_current_smp) {
    if (intra_rank & mask) {
      src = (inter_rank * num_core) + (intra_rank - mask);
      Request::recv(recv_buf, count, dtype, src, tag, comm, &status);
      break;
    }
    mask <<= 1;
  }
  mask >>= 1;

  while (mask > 0) {
    dst = (inter_rank * num_core) + (intra_rank + mask);
    if (dst < comm_size) {
      Request::send(recv_buf, count, dtype, dst, tag, comm);
    }
    mask >>= 1;
  }

  smpi_free_tmp_buffer(tmp_buf);
  return MPI_SUCCESS;
}
}
}
