#include "colls_private.h"
/* 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
   The communication are done in a pipeline fashion */

/* change number of core per smp-node
   we assume that number of core per process will be the same for all implementations */
#ifndef NUM_CORE
#define NUM_CORE 8
#endif

/* this is a default segment size for pipelining, 
   but it is typically passed as a command line argument */
int allreduce_smp_binomial_pipeline_segment_size = 4096;

/* ** NOTE **
   This code is modified from allreduce-smp-binomial.c by wrapping the code with pipeline effect as follow
   for (loop over pipelength) {
     smp-binomial main code;
   }
*/

/* ** 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).
*/

/*
This fucntion performs all-reduce operation as follow. ** in a pipeline fashion **
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
*/
int smpi_coll_tuned_allreduce_smp_binomial_pipeline(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;
  MPI_Status status;
  int num_core = NUM_CORE;

  comm_size = smpi_comm_size(comm);
  rank = smpi_comm_rank(comm);
  MPI_Aint extent;
  extent = smpi_datatype_get_extent(dtype);
  tmp_buf = (void *) xbt_malloc(count * extent);

  int intra_rank, inter_rank;
  intra_rank = rank % num_core;
  inter_rank = rank / num_core;

  int phase;
  int send_offset;
  int recv_offset;
  int pcount = allreduce_smp_binomial_pipeline_segment_size;
  if (pcount > count) {
    pcount = count;
  }

  /* 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 */
  smpi_mpi_sendrecv(send_buf, count, dtype, rank, tag,
               recv_buf, count, dtype, rank, tag, comm, &status);

  /* compute pipe length */
  int pipelength;
  pipelength = count / pcount;

  /* pipelining over pipelength (+3 is because we have 4 stages:
     reduce-intra, reduce-inter, bcast-inter, bcast-intra */
  for (phase = 0; phase < pipelength + 3; phase++) {

    /* start binomial reduce intra communication inside each SMP node */
    if (phase < pipelength) {
      mask = 1;
      while (mask < num_core) {
        if ((mask & intra_rank) == 0) {
          src = (inter_rank * num_core) + (intra_rank | mask);
          if (src < comm_size) {
            recv_offset = phase * pcount * extent;
            smpi_mpi_recv(tmp_buf, pcount, dtype, src, tag, comm, &status);
            smpi_op_apply(op, tmp_buf, (char *)recv_buf + recv_offset, &pcount, &dtype);
          }
        } else {
          send_offset = phase * pcount * extent;
          dst = (inter_rank * num_core) + (intra_rank & (~mask));
          smpi_mpi_send((char *)recv_buf + send_offset, pcount, 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 ((phase > 0) && (phase < (pipelength + 1))) {
      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) {
              recv_offset = (phase - 1) * pcount * extent;
              smpi_mpi_recv(tmp_buf, pcount, dtype, src, tag, comm, &status);
              smpi_op_apply(op, tmp_buf, (char *)recv_buf + recv_offset, &pcount, &dtype);
            }
          } else {
            dst = (inter_rank & (~mask)) * num_core;
            send_offset = (phase - 1) * pcount * extent;
            smpi_mpi_send((char *)recv_buf + send_offset, pcount, 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 ((phase > 1) && (phase < (pipelength + 2))) {
      if (intra_rank == 0) {
        mask = 1;
        while (mask < inter_comm_size) {
          if (inter_rank & mask) {
            src = (inter_rank - mask) * num_core;
            recv_offset = (phase - 2) * pcount * extent;
            smpi_mpi_recv((char *)recv_buf + recv_offset, pcount, 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) {
              //printf("Node %d send to node %d when mask is %d\n", rank, dst, mask);
              send_offset = (phase - 2) * pcount * extent;
              smpi_mpi_send((char *)recv_buf + send_offset, pcount, dtype, dst, tag, comm);
            }
          }
          mask >>= 1;
        }
      }
    }

    /* start binomial broadcast intra-communication inside each SMP nodes */
    if (phase > 2) {
      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);
          recv_offset = (phase - 3) * pcount * extent;
          smpi_mpi_recv((char *)recv_buf + recv_offset, pcount, 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) {
          send_offset = (phase - 3) * pcount * extent;
          smpi_mpi_send((char *)recv_buf + send_offset, pcount, dtype, dst, tag, comm);
        }
        mask >>= 1;
      }
    }
  }                             // for phase

  free(tmp_buf);
  return MPI_SUCCESS;
}
