/* -*- Mode: C; c-basic-offset:2 ; indent-tabs-mode:nil -*- */
/*
 * Copyright (c) 2006      The Trustees of Indiana University and Indiana
 *                         University Research and Technology
 *                         Corporation.  All rights reserved.
 * Copyright (c) 2006      The Technical University of Chemnitz. All
 *                         rights reserved.
 * Copyright (c) 2014-2015 Research Organization for Information Science
 *                         and Technology (RIST). All rights reserved.
 * Copyright (c) 2015      Los Alamos National Security, LLC. All rights
 *                         reserved.
 *
 * Author(s): Torsten Hoefler <htor@cs.indiana.edu>
 *
 */
#include "nbc_internal.h"

#ifdef NBC_CACHE_SCHEDULE
/* tree comparison function for schedule cache */
int NBC_Scan_args_compare(NBC_Scan_args *a, NBC_Scan_args *b, void *param) {
  if ((a->sendbuf == b->sendbuf) &&
      (a->recvbuf == b->recvbuf) &&
      (a->count == b->count) &&
      (a->datatype == b->datatype) &&
      (a->op == b->op) ) {
    return 0;
  }

  if (a->sendbuf < b->sendbuf) {
    return -1;
  }

  return 1;
}
#endif

/* linear iscan
 * working principle:
 * 1. each node (but node 0) receives from left neighbor
 * 2. performs op
 * 3. all but rank p-1 do sends to it's right neighbor and exits
 *
 */
int ompi_coll_libnbc_iscan(const void* sendbuf, void* recvbuf, int count, MPI_Datatype datatype, MPI_Op op,
                           struct ompi_communicator_t *comm, ompi_request_t ** request,
                           struct mca_coll_base_module_2_1_0_t *module) {
  int rank, p, res;
  ptrdiff_t gap, span;
  NBC_Schedule *schedule;
  char inplace;
  NBC_Handle *handle;
  ompi_coll_libnbc_module_t *libnbc_module = (ompi_coll_libnbc_module_t*) module;

  NBC_IN_PLACE(sendbuf, recvbuf, inplace);

  rank = ompi_comm_rank (comm);
  p = ompi_comm_size (comm);

  if (!inplace) {
    /* copy data to receivebuf */
    res = NBC_Copy (sendbuf, count, datatype, recvbuf, count, datatype, comm);
    if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
      return res;
    }
  }

  res = NBC_Init_handle(comm, &handle, libnbc_module);
  if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
    return res;
  }

#ifdef NBC_CACHE_SCHEDULE
  NBC_Scan_args *args, *found, search;

  /* search schedule in communicator specific tree */
  search.sendbuf = sendbuf;
  search.recvbuf = recvbuf;
  search.count = count;
  search.datatype = datatype;
  search.op = op;
  found = (NBC_Scan_args *) hb_tree_search ((hb_tree *) libnbc_module->NBC_Dict[NBC_SCAN], &search);
  if (NULL == found) {
#endif
    schedule = OBJ_NEW(NBC_Schedule);
    if (OPAL_UNLIKELY(NULL == schedule)) {
      NBC_Return_handle (handle);
      return OMPI_ERR_OUT_OF_RESOURCE;
    }

    /* ensure the schedule is released with the handle */
    handle->schedule = schedule;

    if(rank != 0) {
      span = opal_datatype_span(&datatype->super, count, &gap);
      handle->tmpbuf = malloc (span);
      if (NULL == handle->tmpbuf) {
        NBC_Return_handle (handle);
        return OMPI_ERR_OUT_OF_RESOURCE;
      }

      /* we have to wait until we have the data */
      res = NBC_Sched_recv ((void *)(-gap), true, count, datatype, rank-1, schedule, true);
      if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
        NBC_Return_handle (handle);
        return res;
      }

      /* perform the reduce in my local buffer */
      /* this cannot be done until handle->tmpbuf is unused :-( so barrier after the op */
      res = NBC_Sched_op ((void *)(-gap), true, recvbuf, false, count, datatype, op, schedule,
                          true);
      if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
        NBC_Return_handle (handle);
        return res;
      }
    }

    if (rank != p-1) {
      res = NBC_Sched_send (recvbuf, false, count, datatype, rank+1, schedule, false);
      if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
        NBC_Return_handle (handle);
        return res;
      }
    }

    res = NBC_Sched_commit (schedule);
    if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
      NBC_Return_handle (handle);
      return res;
    }

#ifdef NBC_CACHE_SCHEDULE
    /* save schedule to tree */
    args = (NBC_Scan_args *) malloc (sizeof (args));
    if (NULL != args) {
      args->sendbuf = sendbuf;
      args->recvbuf = recvbuf;
      args->count = count;
      args->datatype = datatype;
      args->op = op;
      args->schedule = schedule;
      res = hb_tree_insert ((hb_tree *) libnbc_module->NBC_Dict[NBC_SCAN], args, args, 0);
      if (0 == res) {
        OBJ_RETAIN(schedule);

        /* increase number of elements for A2A */
        if (++libnbc_module->NBC_Dict_size[NBC_SCAN] > NBC_SCHED_DICT_UPPER) {
          NBC_SchedCache_dictwipe ((hb_tree *) libnbc_module->NBC_Dict[NBC_SCAN],
                                   &libnbc_module->NBC_Dict_size[NBC_SCAN]);
        }
      } else {
        NBC_Error("error in dict_insert() (%i)", res);
        free (args);
      }
    }
  } else {
    /* found schedule */
    schedule = found->schedule;
    OBJ_RETAIN(schedule);
  }
#endif

  res = NBC_Start(handle, schedule);
  if (OPAL_UNLIKELY(OMPI_SUCCESS != res)) {
    NBC_Return_handle (handle);
    return res;
  }

  *request = (ompi_request_t *) handle;

  /* tmpbuf is freed with the handle */
  return OMPI_SUCCESS;
}
