/* ---------------------------------------------------------------- */
/* (C)Copyright IBM Corp.  2007, 2008                               */
/* ---------------------------------------------------------------- */
/**
 * \file ad_gpfs_wrcoll.c
 * \brief ???
 */

/* -*- Mode: C; c-basic-offset:4 ; -*- */
/*
 *   Copyright (C) 1997 University of Chicago.
 *   See COPYRIGHT notice in top-level directory.
 */

#include "adio.h"
#include "adio_extern.h"
#include "ad_gpfs.h"
#include "ad_gpfs_aggrs.h"

#ifdef BGQPLATFORM
#include <mpix.h>
#endif

#ifdef AGGREGATION_PROFILE
#include "mpe.h"
#endif
#ifdef PROFILE
#include "mpe.h"
#endif

#include <pthread.h>

#ifdef HAVE_GPFS_H
#include <gpfs.h>
#endif
#ifdef HAVE_GPFS_FCNTL_H
#include <gpfs_fcntl.h>
#endif

#include <limits.h>
/* prototypes of functions used for collective writes only. */
static void ADIOI_Exch_and_write(ADIO_File fd, const void *buf, MPI_Datatype
                         datatype, int nprocs, int myrank, ADIOI_Access
                         *others_req, ADIO_Offset *offset_list,
                         ADIO_Offset *len_list, int contig_access_count, ADIO_Offset
                         min_st_offset, ADIO_Offset fd_size,
                         ADIO_Offset *fd_start, ADIO_Offset *fd_end,
                         int *buf_idx, int *error_code);
static void ADIOI_W_Exchange_data(ADIO_File fd, const void *buf, char *write_buf,
                         ADIOI_Flatlist_node *flat_buf, ADIO_Offset
                         *offset_list, ADIO_Offset *len_list, int *send_size,
                         int *recv_size, ADIO_Offset off, int size,
                         int *count, int *start_pos, int *partial_recv,
                         int *sent_to_proc, int nprocs,
                         int myrank, int
                         buftype_is_contig, int contig_access_count,
                         ADIO_Offset min_st_offset, ADIO_Offset fd_size,
                         ADIO_Offset *fd_start, ADIO_Offset *fd_end,
                         ADIOI_Access *others_req,
                         int *send_buf_idx, int *curr_to_proc,
                         int *done_to_proc, int *hole, int iter,
                         MPI_Aint buftype_extent, int *buf_idx, int *error_code);
static void ADIOI_W_Exchange_data_alltoallv(
		ADIO_File fd, const void *buf,
		char *write_buf,					/* 1 */
		ADIOI_Flatlist_node *flat_buf,
		ADIO_Offset *offset_list,
		ADIO_Offset *len_list, int *send_size, int *recv_size,
		ADIO_Offset off, int size,				/* 2 */
		int *count, int *start_pos, int *partial_recv,
		int *sent_to_proc, int nprocs, int myrank,
		int buftype_is_contig, int contig_access_count,
		ADIO_Offset min_st_offset,
		ADIO_Offset fd_size,
		ADIO_Offset *fd_start,
		ADIO_Offset *fd_end,
		ADIOI_Access *others_req,
		int *send_buf_idx, int *curr_to_proc,			/* 3 */
		int *done_to_proc, int *hole, 				/* 4 */
		int iter, MPI_Aint buftype_extent, int *buf_idx,
		int *error_code);
static void ADIOI_Fill_send_buffer(ADIO_File fd, const void *buf, ADIOI_Flatlist_node
                           *flat_buf, char **send_buf, ADIO_Offset
                           *offset_list, ADIO_Offset *len_list, int *send_size,
                           MPI_Request *requests, int *sent_to_proc,
                           int nprocs, int myrank,
                           int contig_access_count, ADIO_Offset
                           min_st_offset, ADIO_Offset fd_size,
                           ADIO_Offset *fd_start, ADIO_Offset *fd_end,
                           int *send_buf_idx, int *curr_to_proc,
                           int *done_to_proc, int iter,
                           MPI_Aint buftype_extent);
static void ADIOI_Fill_send_buffer_nosend(ADIO_File fd, const void *buf, ADIOI_Flatlist_node
                           *flat_buf, char **send_buf, ADIO_Offset
                           *offset_list, ADIO_Offset *len_list, int *send_size,
                           MPI_Request *requests, int *sent_to_proc,
                           int nprocs, int myrank,
                           int contig_access_count, ADIO_Offset
                           min_st_offset, ADIO_Offset fd_size,
                           ADIO_Offset *fd_start, ADIO_Offset *fd_end,
                           int *send_buf_idx, int *curr_to_proc,
                           int *done_to_proc, int iter,
                           MPI_Aint buftype_extent);
static void ADIOI_Heap_merge(ADIOI_Access *others_req, int *count,
                      ADIO_Offset *srt_off, int *srt_len, int *start_pos,
                      int nprocs, int nprocs_recv, int total_elements);


void ADIOI_GPFS_WriteStridedColl(ADIO_File fd, const void *buf, int count,
                       MPI_Datatype datatype, int file_ptr_type,
                       ADIO_Offset offset, ADIO_Status *status, int
                       *error_code)
{
/* Uses a generalized version of the extended two-phase method described
   in "An Extended Two-Phase Method for Accessing Sections of
   Out-of-Core Arrays", Rajeev Thakur and Alok Choudhary,
   Scientific Programming, (5)4:301--317, Winter 1996.
   http://www.mcs.anl.gov/home/thakur/ext2ph.ps */

    ADIOI_Access *my_req;
    /* array of nprocs access structures, one for each other process in
       whose file domain this process's request lies */

    ADIOI_Access *others_req;
    /* array of nprocs access structures, one for each other process
       whose request lies in this process's file domain. */

    int i, filetype_is_contig, nprocs, nprocs_for_coll, myrank;
    int contig_access_count=0, interleave_count = 0, buftype_is_contig;
    int *count_my_req_per_proc, count_my_req_procs, count_others_req_procs;
    ADIO_Offset orig_fp, start_offset, end_offset, fd_size, min_st_offset, off;
    ADIO_Offset *offset_list = NULL, *st_offsets = NULL, *fd_start = NULL,
	*fd_end = NULL, *end_offsets = NULL;
    ADIO_Offset *gpfs_offsets0 = NULL, *gpfs_offsets = NULL;
    int  ii;

    int *buf_idx = NULL;
    ADIO_Offset *len_list = NULL;
    GPFSMPIO_T_CIO_RESET( w )
#ifdef PROFILE
	MPE_Log_event(13, 0, "start computation");
#endif

    MPI_Comm_size(fd->comm, &nprocs);
    MPI_Comm_rank(fd->comm, &myrank);

/* the number of processes that actually perform I/O, nprocs_for_coll,
 * is stored in the hints off the ADIO_File structure
 */
    nprocs_for_coll = fd->hints->cb_nodes;
    orig_fp = fd->fp_ind;

    GPFSMPIO_T_CIO_SET_GET( w, 1, 0, GPFSMPIO_CIO_T_MPIO_CRW, GPFSMPIO_CIO_LAST)
    GPFSMPIO_T_CIO_SET_GET( w, 1, 0, GPFSMPIO_CIO_T_LCOMP, GPFSMPIO_CIO_LAST )


    /* only check for interleaving if cb_write isn't disabled */
    if (fd->hints->cb_write != ADIOI_HINT_DISABLE) {
	/* For this process's request, calculate the list of offsets and
	   lengths in the file and determine the start and end offsets. */

	/* Note: end_offset points to the last byte-offset that will be accessed.
	   e.g., if start_offset=0 and 100 bytes to be read, end_offset=99*/

	ADIOI_Calc_my_off_len(fd, count, datatype, file_ptr_type, offset,
			      &offset_list, &len_list, &start_offset,
			      &end_offset, &contig_access_count);

    GPFSMPIO_T_CIO_SET_GET( w, 1, 1, GPFSMPIO_CIO_T_GATHER, GPFSMPIO_CIO_T_LCOMP )

	/* each process communicates its start and end offsets to other
	   processes. The result is an array each of start and end offsets stored
	   in order of process rank. */

	st_offsets = (ADIO_Offset *) ADIOI_Malloc(nprocs*sizeof(ADIO_Offset));
	end_offsets = (ADIO_Offset *) ADIOI_Malloc(nprocs*sizeof(ADIO_Offset));

    if (gpfsmpio_tunegather) {
            gpfs_offsets0 = (ADIO_Offset *) ADIOI_Malloc(2*nprocs*sizeof(ADIO_Offset));
            gpfs_offsets  = (ADIO_Offset *) ADIOI_Malloc(2*nprocs*sizeof(ADIO_Offset));
            for (ii=0; ii<nprocs; ii++)  {
                gpfs_offsets0[ii*2]   = 0;
                gpfs_offsets0[ii*2+1] = 0;
            }
            gpfs_offsets0[myrank*2]   = start_offset;
            gpfs_offsets0[myrank*2+1] =   end_offset;

        MPI_Allreduce( gpfs_offsets0, gpfs_offsets, nprocs*2, ADIO_OFFSET, MPI_MAX, fd->comm );

            for (ii=0; ii<nprocs; ii++)  {
                st_offsets [ii] = gpfs_offsets[ii*2]  ;
                end_offsets[ii] = gpfs_offsets[ii*2+1];
            }
            ADIOI_Free( gpfs_offsets0 );
            ADIOI_Free( gpfs_offsets  );
    } else {
	MPI_Allgather(&start_offset, 1, ADIO_OFFSET, st_offsets, 1,
		      ADIO_OFFSET, fd->comm);
	MPI_Allgather(&end_offset, 1, ADIO_OFFSET, end_offsets, 1,
		      ADIO_OFFSET, fd->comm);
    }

    GPFSMPIO_T_CIO_SET_GET(w, 1, 1, GPFSMPIO_CIO_T_PATANA, GPFSMPIO_CIO_T_GATHER )

	/* are the accesses of different processes interleaved? */
	for (i=1; i<nprocs; i++)
      if ((st_offsets[i] < end_offsets[i-1]) &&
                (st_offsets[i] <= end_offsets[i]))
                interleave_count++;
	/* This is a rudimentary check for interleaving, but should suffice
	   for the moment. */
    }

    ADIOI_Datatype_iscontig(datatype, &buftype_is_contig);

    if (fd->hints->cb_write == ADIOI_HINT_DISABLE ||
	(!interleave_count && (fd->hints->cb_write == ADIOI_HINT_AUTO)))
    {
	/* use independent accesses */
	if (fd->hints->cb_write != ADIOI_HINT_DISABLE) {
	    ADIOI_Free(offset_list);
	    ADIOI_Free(len_list);
	    ADIOI_Free(st_offsets);
	    ADIOI_Free(end_offsets);
	}

	fd->fp_ind = orig_fp;
        ADIOI_Datatype_iscontig(fd->filetype, &filetype_is_contig);

        if (buftype_is_contig && filetype_is_contig) {

            if (file_ptr_type == ADIO_EXPLICIT_OFFSET) {
                off = fd->disp + (ADIO_Offset)(fd->etype_size) * offset;
                ADIO_WriteContig(fd, buf, count, datatype,
				 ADIO_EXPLICIT_OFFSET,
				 off, status, error_code);
            }
            else ADIO_WriteContig(fd, buf, count, datatype, ADIO_INDIVIDUAL,
				  0, status, error_code);
        }
	else ADIO_WriteStrided(fd, buf, count, datatype, file_ptr_type,
			       offset, status, error_code);

	return;
    }

    GPFSMPIO_T_CIO_SET_GET( w, 1, 1, GPFSMPIO_CIO_T_FD_PART, GPFSMPIO_CIO_T_PATANA )

/* Divide the I/O workload among "nprocs_for_coll" processes. This is
   done by (logically) dividing the file into file domains (FDs); each
   process may directly access only its own file domain. */

    if (gpfsmpio_tuneblocking)
    ADIOI_GPFS_Calc_file_domains(fd, st_offsets, end_offsets, nprocs,
			    nprocs_for_coll, &min_st_offset,
			    &fd_start, &fd_end, &fd_size, fd->fs_ptr);
    else
    ADIOI_Calc_file_domains(st_offsets, end_offsets, nprocs,
			    nprocs_for_coll, &min_st_offset,
			    &fd_start, &fd_end,
			    fd->hints->min_fdomain_size, &fd_size,
			    fd->hints->striping_unit);

    GPFSMPIO_T_CIO_SET_GET( w, 1, 1, GPFSMPIO_CIO_T_MYREQ, GPFSMPIO_CIO_T_FD_PART );

    if (gpfsmpio_p2pcontig==1) {
	/* For some simple yet common(?) workloads, full-on two-phase I/O is overkill.  We can establish sub-groups of processes and their aggregator, and then these sub-groups will carry out a simplified two-phase over that sub-group.
	 *
	 * First verify that the filetype is contig and the offsets are
	 * increasing in rank order*/
	int i, inOrderAndNoGaps = 1;
	for (i=0;i<(nprocs-1);i++) {
	    if (end_offsets[i] != (st_offsets[i+1]-1))
		inOrderAndNoGaps = 0;
	}
	if (inOrderAndNoGaps && buftype_is_contig) {
	    /* if these conditions exist then execute the P2PContig code else
	     * execute the original code */
	    ADIOI_P2PContigWriteAggregation(fd, buf,
		    error_code, st_offsets, end_offsets, fd_start, fd_end);
	    /* NOTE: we are skipping the rest of two-phase in this path */
            GPFSMPIO_T_CIO_REPORT( 1, fd, myrank, nprocs)

            ADIOI_Free(offset_list);
            ADIOI_Free(len_list);
            ADIOI_Free(st_offsets);
            ADIOI_Free(end_offsets);
            ADIOI_Free(fd_start);
            ADIOI_Free(fd_end);

	    goto fn_exit;
	}
    }

/* calculate what portions of the access requests of this process are
   located in what file domains */

    if (gpfsmpio_tuneblocking)
    ADIOI_GPFS_Calc_my_req(fd, offset_list, len_list, contig_access_count,
		      min_st_offset, fd_start, fd_end, fd_size,
		      nprocs, &count_my_req_procs,
		      &count_my_req_per_proc, &my_req,
		      &buf_idx);
    else
    ADIOI_Calc_my_req(fd, offset_list, len_list, contig_access_count,
		      min_st_offset, fd_start, fd_end, fd_size,
		      nprocs, &count_my_req_procs,
		      &count_my_req_per_proc, &my_req,
		      &buf_idx);

    GPFSMPIO_T_CIO_SET_GET( w, 1, 1, GPFSMPIO_CIO_T_OTHREQ, GPFSMPIO_CIO_T_MYREQ )

/* based on everyone's my_req, calculate what requests of other
   processes lie in this process's file domain.
   count_others_req_procs = number of processes whose requests lie in
   this process's file domain (including this process itself)
   count_others_req_per_proc[i] indicates how many separate contiguous
   requests of proc. i lie in this process's file domain. */

    if (gpfsmpio_tuneblocking)
	ADIOI_GPFS_Calc_others_req(fd, count_my_req_procs,
			      count_my_req_per_proc, my_req,
			      nprocs, myrank,
			      &count_others_req_procs, &others_req);
    else
    ADIOI_Calc_others_req(fd, count_my_req_procs,
			  count_my_req_per_proc, my_req,
			  nprocs, myrank,
			  &count_others_req_procs, &others_req);

    GPFSMPIO_T_CIO_SET_GET( w, 1, 1, GPFSMPIO_CIO_T_DEXCH, GPFSMPIO_CIO_T_OTHREQ )

    ADIOI_Free(count_my_req_per_proc);
    for (i=0; i < nprocs; i++) {
	if (my_req[i].count) {
	    ADIOI_Free(my_req[i].offsets);
	    ADIOI_Free(my_req[i].lens);
	}
    }
    ADIOI_Free(my_req);

/* exchange data and write in sizes of no more than coll_bufsize. */
    ADIOI_Exch_and_write(fd, buf, datatype, nprocs, myrank,
                        others_req, offset_list,
			len_list, contig_access_count, min_st_offset,
			fd_size, fd_start, fd_end, buf_idx, error_code);

    GPFSMPIO_T_CIO_SET_GET( w, 0, 1, GPFSMPIO_CIO_LAST, GPFSMPIO_CIO_T_DEXCH )
    GPFSMPIO_T_CIO_SET_GET( w, 0, 1, GPFSMPIO_CIO_LAST, GPFSMPIO_CIO_T_MPIO_CRW )

    GPFSMPIO_T_CIO_REPORT( 1, fd, myrank, nprocs)

/* free all memory allocated for collective I/O */
    if (!buftype_is_contig) ADIOI_Delete_flattened(datatype);

    for (i=0; i<nprocs; i++) {
	if (others_req[i].count) {
	    ADIOI_Free(others_req[i].offsets);
	    ADIOI_Free(others_req[i].lens);
	    ADIOI_Free(others_req[i].mem_ptrs);
	}
    }
    ADIOI_Free(others_req);

    ADIOI_Free(buf_idx);
    ADIOI_Free(offset_list);
    ADIOI_Free(len_list);
    ADIOI_Free(st_offsets);
    ADIOI_Free(end_offsets);
    ADIOI_Free(fd_start);
    ADIOI_Free(fd_end);

fn_exit:
#ifdef HAVE_STATUS_SET_BYTES
    if (status) {
      MPI_Count bufsize, size;
      /* Don't set status if it isn't needed */
      MPI_Type_size_x(datatype, &size);
      bufsize = size * count;
      MPIR_Status_set_bytes(status, datatype, bufsize);
    }
/* This is a temporary way of filling in status. The right way is to
   keep track of how much data was actually written during collective I/O. */
#endif

    fd->fp_sys_posn = -1;   /* set it to null. */
#ifdef AGGREGATION_PROFILE
	MPE_Log_event (5013, 0, NULL);
#endif
}

static void gpfs_wr_access_start(int fd, ADIO_Offset offset, ADIO_Offset length)
{
        int rc=0;
#ifdef HAVE_GPFS_FCNTL_H
        struct {
                gpfsFcntlHeader_t header;
                gpfsAccessRange_t access;
        } take_locks;

        take_locks.header.totalLength = sizeof(take_locks);
        take_locks.header.fcntlVersion = GPFS_FCNTL_CURRENT_VERSION;
        take_locks.header.fcntlReserved = 0;

        take_locks.access.structLen = sizeof(take_locks.access);
        take_locks.access.structType = GPFS_ACCESS_RANGE;
        take_locks.access.start = offset;
        take_locks.access.length = length;
        take_locks.access.isWrite = 1;

        rc = gpfs_fcntl(fd, &take_locks);
#endif
        ADIOI_Assert(rc == 0);
}

static void gpfs_wr_access_end(int fd, ADIO_Offset offset, ADIO_Offset length)
{
        int rc=0;
#ifdef HAVE_GPFS_FCNTL_H
        struct {
                gpfsFcntlHeader_t header;
                gpfsFreeRange_t free;
        } free_locks;


        free_locks.header.totalLength = sizeof(free_locks);
        free_locks.header.fcntlVersion = GPFS_FCNTL_CURRENT_VERSION;
        free_locks.header.fcntlReserved = 0;

        free_locks.free.structLen = sizeof(free_locks.free);
        free_locks.free.structType = GPFS_FREE_RANGE;
        free_locks.free.start = offset;
        free_locks.free.length = length;

        rc = gpfs_fcntl(fd, &free_locks);
#endif
        ADIOI_Assert(rc == 0);
}

#ifdef BGQPLATFORM
/* my_start, my_end: this processes file domain.  coudd be -1,-1 for "no i/o"
 * fd_start, fd_end: arrays of length fd->hints->cb_nodes specifying all file domains */
static int gpfs_find_access_for_ion(ADIO_File fd,
	ADIO_Offset my_start, ADIO_Offset my_end,
	ADIO_Offset *fd_start, ADIO_Offset *fd_end,
	ADIO_Offset *start, ADIO_Offset *end)
{
    int my_ionode = MPIX_IO_node_id();
    int *rank_to_ionode;
    int i, nprocs, rank;
    ADIO_Offset group_start=LLONG_MAX, group_end=0;

    MPI_Comm_size(fd->comm, &nprocs);
    MPI_Comm_rank(fd->comm, &rank);

    rank_to_ionode = ADIOI_Calloc(nprocs, sizeof(int));
    MPI_Allgather(&my_ionode, 1, MPI_INT,  rank_to_ionode, 1, MPI_INT, fd->comm);

    /* rank_to_ionode now contains a mapping from MPI rank to IO node */
    /* fd->hints->ranklist[] contains a list of MPI ranks that are aggregators */
    /* fd_start[] and fd_end[] contain a list of file domains. */

    /* what we really want to do is take all the file domains associated
     * with a given i/o node and find the begin/end of that range.
     *
     * Because gpfs_fcntl hints are expected to be released, we'll pass this
     * start/end back to the caller, who will both declare and free this range
     */
    if (my_start == -1 || my_end == -1) {
	ADIOI_Free(rank_to_ionode);
	return 0; /* no work to do */
    }

    for (i=0; i<fd->hints->cb_nodes; i++ ){
	if (my_ionode == rank_to_ionode[fd->hints->ranklist[i]] ) {
	    group_start = ADIOI_MIN(fd_start[i], group_start);
	    group_end = ADIOI_MAX(fd_end[i], group_end);
	}
    }
    *start = group_start;
    *end = group_end;
    ADIOI_Free(rank_to_ionode);
    return 1;
}
#endif // BGQPLATFORM


/* If successful, error_code is set to MPI_SUCCESS.  Otherwise an error
 * code is created and returned in error_code.
 */
static void ADIOI_Exch_and_write(ADIO_File fd, const void *buf, MPI_Datatype
				 datatype, int nprocs,
				 int myrank,
				 ADIOI_Access
				 *others_req, ADIO_Offset *offset_list,
				 ADIO_Offset *len_list, int contig_access_count,
				 ADIO_Offset min_st_offset, ADIO_Offset fd_size,
				 ADIO_Offset *fd_start, ADIO_Offset *fd_end,
				 int *buf_idx, int *error_code)
{
/* Send data to appropriate processes and write in sizes of no more
   than coll_bufsize.
   The idea is to reduce the amount of extra memory required for
   collective I/O. If all data were written all at once, which is much
   easier, it would require temp space more than the size of user_buf,
   which is often unacceptable. For example, to write a distributed
   array to a file, where each local array is 8Mbytes, requiring
   at least another 8Mbytes of temp space is unacceptable. */

    /* Not convinced end_loc-st_loc couldn't be > int, so make these offsets*/
    ADIO_Offset size=0;
    int hole, i, j, m, ntimes, max_ntimes, buftype_is_contig;
    ADIO_Offset st_loc=-1, end_loc=-1, off, done, req_off;
    char *write_buf=NULL, *write_buf2=NULL;
    int *curr_offlen_ptr, *count, *send_size, req_len, *recv_size;
    int *partial_recv, *sent_to_proc, *start_pos, flag;
    int *send_buf_idx, *curr_to_proc, *done_to_proc;
    MPI_Status status;
    ADIOI_Flatlist_node *flat_buf=NULL;
    MPI_Aint buftype_extent;
    int info_flag, coll_bufsize;
    char *value;
    static char myname[] = "ADIOI_EXCH_AND_WRITE";
    pthread_t io_thread;
    void *thread_ret;
    ADIOI_IO_ThreadFuncData io_thread_args;

    *error_code = MPI_SUCCESS;  /* changed below if error */
    /* only I/O errors are currently reported */

/* calculate the number of writes of size coll_bufsize
   to be done by each process and the max among all processes.
   That gives the no. of communication phases as well. */

    value = (char *) ADIOI_Malloc((MPI_MAX_INFO_VAL+1)*sizeof(char));
    ADIOI_Info_get(fd->info, "cb_buffer_size", MPI_MAX_INFO_VAL, value,
                 &info_flag);
    coll_bufsize = atoi(value);
    ADIOI_Free(value);

    if (gpfsmpio_pthreadio == 1){
	/* ROMIO will spawn an additional thread. both threads use separate
	 * halves of the collective buffer*/
	coll_bufsize = coll_bufsize/2;
    }

    for (i=0; i < nprocs; i++) {
	if (others_req[i].count) {
	    st_loc = others_req[i].offsets[0];
	    end_loc = others_req[i].offsets[0];
	    break;
	}
    }

    for (i=0; i < nprocs; i++)
	for (j=0; j < others_req[i].count; j++) {
	    st_loc = ADIOI_MIN(st_loc, others_req[i].offsets[j]);
	    end_loc = ADIOI_MAX(end_loc, (others_req[i].offsets[j]
				       + others_req[i].lens[j] - 1));
	}

/* ntimes=ceiling_div(end_loc - st_loc + 1, coll_bufsize)*/

    ntimes = (int) ((end_loc - st_loc + coll_bufsize)/coll_bufsize);

    if ((st_loc==-1) && (end_loc==-1)) {
	ntimes = 0; /* this process does no writing. */
    }
    if (ntimes > 0) { /* only set the gpfs hint if we have io - ie this rank is
			 an aggregator -- otherwise will fail for deferred open */
      if (getenv("ROMIO_GPFS_DECLARE_ACCESS")!=NULL) {
	gpfs_wr_access_start(fd->fd_sys, st_loc, end_loc - st_loc);
      }
    }

    ADIO_Offset st_loc_ion=0, end_loc_ion=0, needs_gpfs_access_cleanup=0;
#ifdef BGQPLATFORM
    if (ntimes > 0) { /* only set the gpfs hint if we have io - ie this rank is
			 an aggregator -- otherwise will fail for deferred open */

      if (getenv("ROMIO_GPFS_DECLARE_ION_ACCESS")!=NULL) {
	if (gpfs_find_access_for_ion(fd, st_loc, end_loc, fd_start, fd_end,
		    &st_loc_ion, &end_loc_ion)) {
	    gpfs_wr_access_start(fd->fd_sys, st_loc_ion, end_loc_ion-st_loc_ion);
	    needs_gpfs_access_cleanup=1;
	}
      }
    }
#endif

    MPI_Allreduce(&ntimes, &max_ntimes, 1, MPI_INT, MPI_MAX,
		  fd->comm);

    write_buf = fd->io_buf;
    if (gpfsmpio_pthreadio == 1) {
	write_buf2 = fd->io_buf + coll_bufsize;
    }

    curr_offlen_ptr = (int *) ADIOI_Calloc(nprocs, sizeof(int));
    /* its use is explained below. calloc initializes to 0. */

    count = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    /* to store count of how many off-len pairs per proc are satisfied
       in an iteration. */

    partial_recv = (int *) ADIOI_Calloc(nprocs, sizeof(int));
    /* if only a portion of the last off-len pair is recd. from a process
       in a particular iteration, the length recd. is stored here.
       calloc initializes to 0. */

    send_size = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    /* total size of data to be sent to each proc. in an iteration.
       Of size nprocs so that I can use MPI_Alltoall later. */

    recv_size = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    /* total size of data to be recd. from each proc. in an iteration.*/

    sent_to_proc = (int *) ADIOI_Calloc(nprocs, sizeof(int));
    /* amount of data sent to each proc so far. Used in
       ADIOI_Fill_send_buffer. initialized to 0 here. */

    send_buf_idx = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    curr_to_proc = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    done_to_proc = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    /* Above three are used in ADIOI_Fill_send_buffer*/

    start_pos = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    /* used to store the starting value of curr_offlen_ptr[i] in
       this iteration */

    ADIOI_Datatype_iscontig(datatype, &buftype_is_contig);
    if (!buftype_is_contig) {
	ADIOI_Flatten_datatype(datatype);
	flat_buf = ADIOI_Flatlist;
        while (flat_buf->type != datatype) flat_buf = flat_buf->next;
    }
    MPI_Type_extent(datatype, &buftype_extent);


/* I need to check if there are any outstanding nonblocking writes to
   the file, which could potentially interfere with the writes taking
   place in this collective write call. Since this is not likely to be
   common, let me do the simplest thing possible here: Each process
   completes all pending nonblocking operations before completing. */

    /*ADIOI_Complete_async(error_code);
    if (*error_code != MPI_SUCCESS) return;
    MPI_Barrier(fd->comm);
    */

    done = 0;
    off = st_loc;

    if(gpfsmpio_pthreadio == 1)
	io_thread = pthread_self();

#ifdef PROFILE
	MPE_Log_event(14, 0, "end computation");
#endif

    for (m=0; m < ntimes; m++) {
       /* go through all others_req and check which will be satisfied
          by the current write */

       /* Note that MPI guarantees that displacements in filetypes are in
          monotonically nondecreasing order and that, for writes, the
	  filetypes cannot specify overlapping regions in the file. This
	  simplifies implementation a bit compared to reads. */

          /* off = start offset in the file for the data to be written in
                   this iteration
             size = size of data written (bytes) corresponding to off
             req_off = off in file for a particular contiguous request
                       minus what was satisfied in previous iteration
             req_size = size corresponding to req_off */

	/* first calculate what should be communicated */

#ifdef PROFILE
	MPE_Log_event(13, 0, "start computation");
#endif
	for (i=0; i < nprocs; i++) count[i] = recv_size[i] = 0;

	size = ADIOI_MIN((unsigned)coll_bufsize, end_loc-st_loc+1-done);

	for (i=0; i < nprocs; i++) {
	    if (others_req[i].count) {
		start_pos[i] = curr_offlen_ptr[i];
		for (j=curr_offlen_ptr[i]; j<others_req[i].count; j++) {
		    if (partial_recv[i]) {
			/* this request may have been partially
			   satisfied in the previous iteration. */
			req_off = others_req[i].offsets[j] +
			    partial_recv[i];
                        req_len = others_req[i].lens[j] -
			    partial_recv[i];
			partial_recv[i] = 0;
			/* modify the off-len pair to reflect this change */
			others_req[i].offsets[j] = req_off;
			others_req[i].lens[j] = req_len;
		    }
		    else {
			req_off = others_req[i].offsets[j];
                        req_len = others_req[i].lens[j];
		    }
		    if (req_off < off + size) {
			count[i]++;
      ADIOI_Assert((((ADIO_Offset)(MPIR_Upint)write_buf)+req_off-off) == (ADIO_Offset)(MPIR_Upint)(write_buf+req_off-off));
			MPI_Address(write_buf+req_off-off,
                               &(others_req[i].mem_ptrs[j]));
      ADIOI_Assert((off + size - req_off) == (int)(off + size - req_off));
			recv_size[i] += (int)(ADIOI_MIN(off + size - req_off,
                                      (unsigned)req_len));

			if (off+size-req_off < (unsigned)req_len)
			{
			    partial_recv[i] = (int) (off + size - req_off);

			    /* --BEGIN ERROR HANDLING-- */
			    if ((j+1 < others_req[i].count) &&
                                 (others_req[i].offsets[j+1] < off+size))
			    {
				*error_code = MPIO_Err_create_code(MPI_SUCCESS,
								   MPIR_ERR_RECOVERABLE,
								   myname,
								   __LINE__,
								   MPI_ERR_ARG,
								   "Filetype specifies overlapping write regions (which is illegal according to the MPI-2 specification)", 0);
				/* allow to continue since additional
				 * communication might have to occur
				 */
			    }
			    /* --END ERROR HANDLING-- */
			    break;
			}
		    }
		    else break;
		}
		curr_offlen_ptr[i] = j;
	    }
	}

#ifdef PROFILE
	MPE_Log_event(14, 0, "end computation");
	MPE_Log_event(7, 0, "start communication");
#endif
        if (gpfsmpio_comm == 1)
	ADIOI_W_Exchange_data(fd, buf, write_buf, flat_buf, offset_list,
                            len_list, send_size, recv_size, off, size, count,
                            start_pos, partial_recv,
                            sent_to_proc, nprocs, myrank,
			    buftype_is_contig, contig_access_count,
			    min_st_offset, fd_size, fd_start, fd_end,
			    others_req, send_buf_idx, curr_to_proc,
                            done_to_proc, &hole, m, buftype_extent, buf_idx,
			    error_code);
	else
        if (gpfsmpio_comm == 0)
	ADIOI_W_Exchange_data_alltoallv(fd, buf, write_buf, flat_buf, offset_list,
                            len_list, send_size, recv_size, off, size, count,
                            start_pos, partial_recv,
                            sent_to_proc, nprocs, myrank,
			    buftype_is_contig, contig_access_count,
			    min_st_offset, fd_size, fd_start, fd_end,
			    others_req, send_buf_idx, curr_to_proc,
                            done_to_proc, &hole, m, buftype_extent, buf_idx,
			    error_code);
        if (*error_code != MPI_SUCCESS) return;
#ifdef PROFILE
	MPE_Log_event(8, 0, "end communication");
#endif

	flag = 0;
	for (i=0; i<nprocs; i++)
	    if (count[i]) flag = 1;

	if (flag) {
	    char round[50];
	    sprintf(round, "two-phase-round=%d", m);
	    setenv("LIBIOLOG_EXTRA_INFO", round, 1);
      ADIOI_Assert(size == (int)size);
	    if (gpfsmpio_pthreadio == 1) {
		/* there is no such thing as "invalid pthread identifier", so
		 * we'll use pthread_self() instead.  Before we do I/O we want
		 * to complete I/O from any previous iteration -- but only a
		 * previous iteration that had I/O work to do (i.e. set 'flag')
		 */
		if(!pthread_equal(io_thread, pthread_self())) {
		    pthread_join(io_thread, &thread_ret);
		    *error_code = *(int *)thread_ret;
		    if (*error_code != MPI_SUCCESS) return;
		    io_thread = pthread_self();

		}
		io_thread_args.fd = fd;
		/* do a little pointer shuffling: background I/O works from one
		 * buffer while two-phase machinery fills up another */
		io_thread_args.buf = write_buf;
		ADIOI_SWAP(write_buf, write_buf2, char*);
		io_thread_args.io_kind = ADIOI_WRITE;
		io_thread_args.size = size;
		io_thread_args.offset = off;
		io_thread_args.status = status;
		io_thread_args.error_code = *error_code;
		if ( (pthread_create(&io_thread, NULL,
			ADIOI_IO_Thread_Func, &(io_thread_args))) != 0)
		    io_thread = pthread_self();
	    } else {
		ADIO_WriteContig(fd, write_buf, (int)size, MPI_BYTE,
			ADIO_EXPLICIT_OFFSET, off, &status, error_code);
		if (*error_code != MPI_SUCCESS) return;
	    }
	}

	off += size;
	done += size;
    }
    if (gpfsmpio_pthreadio == 1) {
	if ( !pthread_equal(io_thread, pthread_self()) ) {
	    pthread_join(io_thread, &thread_ret);
	    *error_code = *(int *)thread_ret;
	}
    }

    for (i=0; i<nprocs; i++) count[i] = recv_size[i] = 0;
#ifdef PROFILE
	MPE_Log_event(7, 0, "start communication");
#endif
    for (m=ntimes; m<max_ntimes; m++)
	/* nothing to recv, but check for send. */
        if (gpfsmpio_comm == 1)
	ADIOI_W_Exchange_data(fd, buf, write_buf, flat_buf, offset_list,
                            len_list, send_size, recv_size, off, size, count,
                            start_pos, partial_recv,
                            sent_to_proc, nprocs, myrank,
			    buftype_is_contig, contig_access_count,
			    min_st_offset, fd_size, fd_start, fd_end,
			    others_req, send_buf_idx,
                            curr_to_proc, done_to_proc, &hole, m,
                            buftype_extent, buf_idx, error_code);
	else
        if (gpfsmpio_comm == 0)
	ADIOI_W_Exchange_data_alltoallv(fd, buf, write_buf, flat_buf, offset_list,
                            len_list, send_size, recv_size, off, size, count,
                            start_pos, partial_recv,
                            sent_to_proc, nprocs, myrank,
			    buftype_is_contig, contig_access_count,
			    min_st_offset, fd_size, fd_start, fd_end,
			    others_req, send_buf_idx,
                            curr_to_proc, done_to_proc, &hole, m,
                            buftype_extent, buf_idx, error_code);
        if (*error_code != MPI_SUCCESS) return;
#ifdef PROFILE
	MPE_Log_event(8, 0, "end communication");
#endif

    ADIOI_Free(curr_offlen_ptr);
    ADIOI_Free(count);
    ADIOI_Free(partial_recv);
    ADIOI_Free(send_size);
    ADIOI_Free(recv_size);
    ADIOI_Free(sent_to_proc);
    ADIOI_Free(start_pos);
    ADIOI_Free(send_buf_idx);
    ADIOI_Free(curr_to_proc);
    ADIOI_Free(done_to_proc);

    if (ntimes != 0 && getenv("ROMIO_GPFS_DECLARE_ACCESS")!=NULL) {
	gpfs_wr_access_end(fd->fd_sys, st_loc, end_loc-st_loc);
    }

    if (needs_gpfs_access_cleanup) {
	gpfs_wr_access_end(fd->fd_sys, st_loc_ion, end_loc_ion-st_loc_ion);
	needs_gpfs_access_cleanup=0;
    }

    unsetenv("LIBIOLOG_EXTRA_INFO");
}


/* Sets error_code to MPI_SUCCESS if successful, or creates an error code
 * in the case of error.
 */
static void ADIOI_W_Exchange_data(ADIO_File fd, const void *buf, char *write_buf,
				  ADIOI_Flatlist_node *flat_buf, ADIO_Offset
				  *offset_list, ADIO_Offset *len_list, int *send_size,
				  int *recv_size, ADIO_Offset off, int size,
				  int *count, int *start_pos,
				  int *partial_recv,
				  int *sent_to_proc, int nprocs,
				  int myrank, int
				  buftype_is_contig, int contig_access_count,
				  ADIO_Offset min_st_offset,
				  ADIO_Offset fd_size,
				  ADIO_Offset *fd_start, ADIO_Offset *fd_end,
				  ADIOI_Access *others_req,
				  int *send_buf_idx, int *curr_to_proc,
				  int *done_to_proc, int *hole, int iter,
				  MPI_Aint buftype_extent, int *buf_idx,
				  int *error_code)
{
    int i, j, k, *tmp_len, nprocs_recv, nprocs_send, err;
    char **send_buf = NULL;
    MPI_Request *requests, *send_req;
    MPI_Datatype *recv_types;
    MPI_Status *statuses, status;
    int *srt_len, sum;
    ADIO_Offset *srt_off;
    static char myname[] = "ADIOI_W_EXCHANGE_DATA";

/* exchange recv_size info so that each process knows how much to
   send to whom. */

    MPI_Alltoall(recv_size, 1, MPI_INT, send_size, 1, MPI_INT, fd->comm);

    /* create derived datatypes for recv */

    nprocs_recv = 0;
    for (i=0; i<nprocs; i++) if (recv_size[i]) nprocs_recv++;

    recv_types = (MPI_Datatype *)
	ADIOI_Malloc((nprocs_recv+1)*sizeof(MPI_Datatype));
/* +1 to avoid a 0-size malloc */

    tmp_len = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    j = 0;
    for (i=0; i<nprocs; i++) {
	if (recv_size[i]) {
/* take care if the last off-len pair is a partial recv */
	    if (partial_recv[i]) {
		k = start_pos[i] + count[i] - 1;
		tmp_len[i] = others_req[i].lens[k];
		others_req[i].lens[k] = partial_recv[i];
	    }
	    ADIOI_Type_create_hindexed_x(count[i],
		  &(others_req[i].lens[start_pos[i]]),
	             &(others_req[i].mem_ptrs[start_pos[i]]),
			 MPI_BYTE, recv_types+j);
	    /* absolute displacements; use MPI_BOTTOM in recv */
	    MPI_Type_commit(recv_types+j);
	    j++;
	}
    }

    /* To avoid a read-modify-write, check if there are holes in the
       data to be written. For this, merge the (sorted) offset lists
       others_req using a heap-merge. */

    sum = 0;
    for (i=0; i<nprocs; i++) sum += count[i];
    srt_off = (ADIO_Offset *) ADIOI_Malloc((sum+1)*sizeof(ADIO_Offset));
    srt_len = (int *) ADIOI_Malloc((sum+1)*sizeof(int));
    /* +1 to avoid a 0-size malloc */

    ADIOI_Heap_merge(others_req, count, srt_off, srt_len, start_pos,
                     nprocs, nprocs_recv, sum);

/* for partial recvs, restore original lengths */
    for (i=0; i<nprocs; i++)
        if (partial_recv[i]) {
            k = start_pos[i] + count[i] - 1;
            others_req[i].lens[k] = tmp_len[i];
        }
    ADIOI_Free(tmp_len);

    /* check if there are any holes. If yes, must do read-modify-write.
     * holes can be in three places.  'middle' is what you'd expect: the
     * processes are operating on noncontigous data.  But holes can also show
     * up at the beginning or end of the file domain (see John Bent ROMIO REQ
     * #835). Missing these holes would result in us writing more data than
     * recieved by everyone else. */
    *hole = 0;
    if (off != srt_off[0]) /* hole at the front */
        *hole = 1;
    else { /* coalesce the sorted offset-length pairs */
        for (i=1; i<sum; i++) {
            if (srt_off[i] <= srt_off[0] + srt_len[0]) {
		int new_len = srt_off[i] + srt_len[i] - srt_off[0];
		if (new_len > srt_len[0]) srt_len[0] = new_len;
	    }
            else
                break;
        }
        if (i < sum || size != srt_len[0]) /* hole in middle or end */
            *hole = 1;
	}

    ADIOI_Free(srt_off);
    ADIOI_Free(srt_len);

    if (nprocs_recv) {
	if (*hole) {
	    const char * stuff = "data-sieve-in-two-phase";
	    setenv("LIBIOLOG_EXTRA_INFO", stuff, 1);
	    ADIO_ReadContig(fd, write_buf, size, MPI_BYTE,
			    ADIO_EXPLICIT_OFFSET, off, &status, &err);
	    /* --BEGIN ERROR HANDLING-- */
	    if (err != MPI_SUCCESS) {
		*error_code = MPIO_Err_create_code(err,
						   MPIR_ERR_RECOVERABLE, myname,
						   __LINE__, MPI_ERR_IO,
						   "**ioRMWrdwr", 0);
		return;
	    }
	    /* --END ERROR HANDLING-- */
	    unsetenv("LIBIOLOG_EXTRA_INFO");
	}
    }

    nprocs_send = 0;
    for (i=0; i < nprocs; i++) if (send_size[i]) nprocs_send++;

    if (fd->atomicity) {
        /* bug fix from Wei-keng Liao and Kenin Coloma */
        requests = (MPI_Request *)
	    ADIOI_Malloc((nprocs_send+1)*sizeof(MPI_Request));
        send_req = requests;
    }
    else {
        requests = (MPI_Request *)
            ADIOI_Malloc((nprocs_send+nprocs_recv+1)*sizeof(MPI_Request));
        /* +1 to avoid a 0-size malloc */

        /* post receives */
        j = 0;
        for (i=0; i<nprocs; i++) {
            if (recv_size[i]) {
                MPI_Irecv(MPI_BOTTOM, 1, recv_types[j], i, myrank+i+100*iter,
                          fd->comm, requests+j);
                j++;
            }
        }
	send_req = requests + nprocs_recv;
    }

/* post sends. if buftype_is_contig, data can be directly sent from
   user buf at location given by buf_idx. else use send_buf. */

#ifdef AGGREGATION_PROFILE
    MPE_Log_event (5032, 0, NULL);
#endif
    if (buftype_is_contig) {
	j = 0;
	for (i=0; i < nprocs; i++)
	    if (send_size[i]) {
		MPI_Isend(((char *) buf) + buf_idx[i], send_size[i],
  		            MPI_BYTE, i,  myrank+i+100*iter, fd->comm,
                                  send_req+j);
		j++;
                buf_idx[i] += send_size[i];
	    }
    }
    else if (nprocs_send) {
	/* buftype is not contig */
	send_buf = (char **) ADIOI_Malloc(nprocs*sizeof(char*));
	for (i=0; i < nprocs; i++)
	    if (send_size[i])
		send_buf[i] = (char *) ADIOI_Malloc(send_size[i]);

	ADIOI_Fill_send_buffer(fd, buf, flat_buf, send_buf,
                           offset_list, len_list, send_size,
			   send_req,
                           sent_to_proc, nprocs, myrank,
                           contig_access_count,
                           min_st_offset, fd_size, fd_start, fd_end,
                           send_buf_idx, curr_to_proc, done_to_proc, iter,
                           buftype_extent);
        /* the send is done in ADIOI_Fill_send_buffer */
    }

    if (fd->atomicity) {
        /* bug fix from Wei-keng Liao and Kenin Coloma */
        j = 0;
        for (i=0; i<nprocs; i++) {
            MPI_Status wkl_status;
	    if (recv_size[i]) {
	        MPI_Recv(MPI_BOTTOM, 1, recv_types[j], i, myrank+i+100*iter,
		          fd->comm, &wkl_status);
	        j++;
	    }
        }
    }

    for (i=0; i<nprocs_recv; i++) MPI_Type_free(recv_types+i);
    ADIOI_Free(recv_types);

    if (fd->atomicity) {
        /* bug fix from Wei-keng Liao and Kenin Coloma */
        statuses = (MPI_Status *) ADIOI_Malloc((nprocs_send+1) * \
                                         sizeof(MPI_Status));
         /* +1 to avoid a 0-size malloc */
    }
    else {
        statuses = (MPI_Status *) ADIOI_Malloc((nprocs_send+nprocs_recv+1) * \
                                     sizeof(MPI_Status));
        /* +1 to avoid a 0-size malloc */
    }

#ifdef NEEDS_MPI_TEST
    i = 0;
    if (fd->atomicity) {
        /* bug fix from Wei-keng Liao and Kenin Coloma */
        while (!i) MPI_Testall(nprocs_send, send_req, &i, statuses);
    }
    else {
        while (!i) MPI_Testall(nprocs_send+nprocs_recv, requests, &i, statuses);
    }
#else
    if (fd->atomicity)
        /* bug fix from Wei-keng Liao and Kenin Coloma */
        MPI_Waitall(nprocs_send, send_req, statuses);
    else
        MPI_Waitall(nprocs_send+nprocs_recv, requests, statuses);
#endif

#ifdef AGGREGATION_PROFILE
    MPE_Log_event (5033, 0, NULL);
#endif
    ADIOI_Free(statuses);
    ADIOI_Free(requests);
    if (!buftype_is_contig && nprocs_send) {
	for (i=0; i < nprocs; i++)
	    if (send_size[i]) ADIOI_Free(send_buf[i]);
	ADIOI_Free(send_buf);
    }
}


#define ADIOI_BUF_INCR \
{ \
    while (buf_incr) { \
        size_in_buf = ADIOI_MIN(buf_incr, flat_buf_sz); \
        user_buf_idx += size_in_buf; \
        flat_buf_sz -= size_in_buf; \
        if (!flat_buf_sz) { \
            if (flat_buf_idx < (flat_buf->count - 1)) flat_buf_idx++; \
            else { \
                flat_buf_idx = 0; \
                n_buftypes++; \
            } \
            user_buf_idx = flat_buf->indices[flat_buf_idx] + \
                              (ADIO_Offset)n_buftypes*(ADIO_Offset)buftype_extent; \
            flat_buf_sz = flat_buf->blocklens[flat_buf_idx]; \
        } \
        buf_incr -= size_in_buf; \
    } \
}


#define ADIOI_BUF_COPY \
{ \
    while (size) { \
        size_in_buf = ADIOI_MIN(size, flat_buf_sz); \
  ADIOI_Assert((((ADIO_Offset)(MPIR_Upint)buf) + user_buf_idx) == (ADIO_Offset)(MPIR_Upint)((MPIR_Upint)buf + user_buf_idx)); \
  ADIOI_Assert(size_in_buf == (size_t)size_in_buf); \
        memcpy(&(send_buf[p][send_buf_idx[p]]), \
               ((char *) buf) + user_buf_idx, size_in_buf); \
        send_buf_idx[p] += size_in_buf; \
        user_buf_idx += size_in_buf; \
        flat_buf_sz -= size_in_buf; \
        if (!flat_buf_sz) { \
            if (flat_buf_idx < (flat_buf->count - 1)) flat_buf_idx++; \
            else { \
                flat_buf_idx = 0; \
                n_buftypes++; \
            } \
            user_buf_idx = flat_buf->indices[flat_buf_idx] + \
                              (ADIO_Offset)n_buftypes*(ADIO_Offset)buftype_extent; \
            flat_buf_sz = flat_buf->blocklens[flat_buf_idx]; \
        } \
        size -= size_in_buf; \
        buf_incr -= size_in_buf; \
    } \
    ADIOI_BUF_INCR \
}

static void ADIOI_Fill_send_buffer(ADIO_File fd, const void *buf, ADIOI_Flatlist_node
                           *flat_buf, char **send_buf, ADIO_Offset
                           *offset_list, ADIO_Offset *len_list, int *send_size,
                           MPI_Request *requests, int *sent_to_proc,
                           int nprocs, int myrank,
                           int contig_access_count,
                           ADIO_Offset min_st_offset, ADIO_Offset fd_size,
                           ADIO_Offset *fd_start, ADIO_Offset *fd_end,
                           int *send_buf_idx, int *curr_to_proc,
                           int *done_to_proc, int iter,
                           MPI_Aint buftype_extent)
{
/* this function is only called if buftype is not contig */

    int i, p, flat_buf_idx;
    ADIO_Offset flat_buf_sz, size_in_buf, buf_incr, size;
    int jj, n_buftypes;
    ADIO_Offset off, len, rem_len, user_buf_idx;

/*  curr_to_proc[p] = amount of data sent to proc. p that has already
    been accounted for so far
    done_to_proc[p] = amount of data already sent to proc. p in
    previous iterations
    user_buf_idx = current location in user buffer
    send_buf_idx[p] = current location in send_buf of proc. p  */

    for (i=0; i < nprocs; i++) {
	send_buf_idx[i] = curr_to_proc[i] = 0;
	done_to_proc[i] = sent_to_proc[i];
    }
    jj = 0;

    user_buf_idx = flat_buf->indices[0];
    flat_buf_idx = 0;
    n_buftypes = 0;
    flat_buf_sz = flat_buf->blocklens[0];

    /* flat_buf_idx = current index into flattened buftype
       flat_buf_sz = size of current contiguous component in
	                 flattened buf */

    for (i=0; i<contig_access_count; i++) {
	off     = offset_list[i];
	rem_len = len_list[i];

	/*this request may span the file domains of more than one process*/
  while (rem_len != 0) {
	    len = rem_len;
	    /* NOTE: len value is modified by ADIOI_Calc_aggregator() to be no
	     * longer than the single region that processor "p" is responsible
	     * for.
	     */
	    p = ADIOI_GPFS_Calc_aggregator(fd,
				      off,
				      min_st_offset,
				      &len,
				      fd_size,
				      fd_start,
				      fd_end);

	    if (send_buf_idx[p] < send_size[p]) {
		if (curr_to_proc[p]+len > done_to_proc[p]) {
		    if (done_to_proc[p] > curr_to_proc[p]) {
			size = ADIOI_MIN(curr_to_proc[p] + len -
                                done_to_proc[p], send_size[p]-send_buf_idx[p]);
			buf_incr = done_to_proc[p] - curr_to_proc[p];
			ADIOI_BUF_INCR
      ADIOI_Assert((curr_to_proc[p] + len - done_to_proc[p]) == (unsigned)(curr_to_proc[p] + len - done_to_proc[p]));
		        buf_incr = curr_to_proc[p] + len - done_to_proc[p];
      ADIOI_Assert((done_to_proc[p] + size) == (unsigned)(done_to_proc[p] + size));
			curr_to_proc[p] = done_to_proc[p] + size;
		        ADIOI_BUF_COPY
		    }
		    else {
			size = ADIOI_MIN(len,send_size[p]-send_buf_idx[p]);
			buf_incr = len;
      ADIOI_Assert((curr_to_proc[p] + size) == (unsigned)((ADIO_Offset)curr_to_proc[p] + size));
			curr_to_proc[p] += size;
			ADIOI_BUF_COPY
		    }
		    if (send_buf_idx[p] == send_size[p]) {
			MPI_Isend(send_buf[p], send_size[p], MPI_BYTE, p,
				myrank+p+100*iter, fd->comm, requests+jj);
			jj++;
		    }
		}
		else {
        ADIOI_Assert((curr_to_proc[p] + len) == (unsigned)((ADIO_Offset)curr_to_proc[p] + len));
		    curr_to_proc[p] += len;
		    buf_incr = len;
		    ADIOI_BUF_INCR
		}
	    }
	    else {
		buf_incr = len;
		ADIOI_BUF_INCR
            }
	    off     += len;
	    rem_len -= len;
	}
    }
    for (i=0; i < nprocs; i++)
	if (send_size[i]) sent_to_proc[i] = curr_to_proc[i];
}



static void ADIOI_Heap_merge(ADIOI_Access *others_req, int *count,
		      ADIO_Offset *srt_off, int *srt_len, int *start_pos,
		      int nprocs, int nprocs_recv, int total_elements)
{
    typedef struct {
	ADIO_Offset *off_list;
	ADIO_Offset *len_list;
	int nelem;
    } heap_struct;

    heap_struct *a, tmp;
    int i, j, heapsize, l, r, k, smallest;

    a = (heap_struct *) ADIOI_Malloc((nprocs_recv+1)*sizeof(heap_struct));

    j = 0;
    for (i=0; i<nprocs; i++)
	if (count[i]) {
	    a[j].off_list = &(others_req[i].offsets[start_pos[i]]);
	    a[j].len_list = &(others_req[i].lens[start_pos[i]]);
	    a[j].nelem = count[i];
	    j++;
	}

    /* build a heap out of the first element from each list, with
       the smallest element of the heap at the root */

    heapsize = nprocs_recv;
    for (i=heapsize/2 - 1; i>=0; i--) {
	/* Heapify(a, i, heapsize); Algorithm from Cormen et al. pg. 143
           modified for a heap with smallest element at root. I have
           removed the recursion so that there are no function calls.
           Function calls are too expensive. */
	k = i;
	while (1) {
	    l = 2*(k+1) - 1;
	    r = 2*(k+1);

	    if ((l < heapsize) &&
		(*(a[l].off_list) < *(a[k].off_list)))
		smallest = l;
	    else smallest = k;

	    if ((r < heapsize) &&
		(*(a[r].off_list) < *(a[smallest].off_list)))
		smallest = r;

	    if (smallest != k) {
		tmp.off_list = a[k].off_list;
		tmp.len_list = a[k].len_list;
		tmp.nelem = a[k].nelem;

		a[k].off_list = a[smallest].off_list;
		a[k].len_list = a[smallest].len_list;
		a[k].nelem = a[smallest].nelem;

		a[smallest].off_list = tmp.off_list;
		a[smallest].len_list = tmp.len_list;
		a[smallest].nelem = tmp.nelem;

		k = smallest;
	    }
	    else break;
	}
    }

    for (i=0; i<total_elements; i++) {
        /* extract smallest element from heap, i.e. the root */
	srt_off[i] = *(a[0].off_list);
	srt_len[i] = *(a[0].len_list);
	(a[0].nelem)--;

	if (!a[0].nelem) {
	    a[0].off_list = a[heapsize-1].off_list;
	    a[0].len_list = a[heapsize-1].len_list;
	    a[0].nelem = a[heapsize-1].nelem;
	    heapsize--;
	}
	else {
	    (a[0].off_list)++;
	    (a[0].len_list)++;
	}

	/* Heapify(a, 0, heapsize); */
	k = 0;
	while (1) {
	    l = 2*(k+1) - 1;
	    r = 2*(k+1);

	    if ((l < heapsize) &&
		(*(a[l].off_list) < *(a[k].off_list)))
		smallest = l;
	    else smallest = k;

	    if ((r < heapsize) &&
		(*(a[r].off_list) < *(a[smallest].off_list)))
		smallest = r;

	    if (smallest != k) {
		tmp.off_list = a[k].off_list;
		tmp.len_list = a[k].len_list;
		tmp.nelem = a[k].nelem;

		a[k].off_list = a[smallest].off_list;
		a[k].len_list = a[smallest].len_list;
		a[k].nelem = a[smallest].nelem;

		a[smallest].off_list = tmp.off_list;
		a[smallest].len_list = tmp.len_list;
		a[smallest].nelem = tmp.nelem;

		k = smallest;
	    }
	    else break;
	}
    }

    ADIOI_Free(a);
}


static void ADIOI_W_Exchange_data_alltoallv(
		ADIO_File fd, const void *buf,
		char *write_buf,					/* 1 */
		ADIOI_Flatlist_node *flat_buf,
		ADIO_Offset *offset_list,
		ADIO_Offset *len_list, int *send_size, int *recv_size,
		ADIO_Offset off, int size,				/* 2 */
		int *count, int *start_pos, int *partial_recv,
		int *sent_to_proc, int nprocs, int myrank,
		int buftype_is_contig, int contig_access_count,
		ADIO_Offset min_st_offset,
		ADIO_Offset fd_size,
		ADIO_Offset *fd_start,
		ADIO_Offset *fd_end,
		ADIOI_Access *others_req,
		int *send_buf_idx, int *curr_to_proc,			/* 3 */
		int *done_to_proc, int *hole, 				/* 4 */
		int iter, MPI_Aint buftype_extent, int *buf_idx,
		int *error_code)
{
    int i, j, k=0, nprocs_recv, nprocs_send, *tmp_len, err;
    char **send_buf = NULL;
    MPI_Request *send_req=NULL;
    MPI_Status status;
    int rtail, stail;
    char *sbuf_ptr, *to_ptr;
    int  len;
    int  *sdispls, *rdispls;
    char *all_recv_buf, *all_send_buf;
    int *srt_len, sum;
    ADIO_Offset *srt_off;
    static char myname[] = "ADIOI_W_EXCHANGE_DATA";
    double io_time;

    io_time = MPI_Wtime();
  /* exchange recv_size info so that each process knows how much to
     send to whom. */
    MPI_Alltoall(recv_size, 1, MPI_INT, send_size, 1, MPI_INT, fd->comm);

    gpfsmpio_prof_cw[GPFSMPIO_CIO_T_DEXCH_RECV_EXCH] += MPI_Wtime() - io_time;
    io_time = MPI_Wtime();

    nprocs_recv = 0;
    for (i=0; i<nprocs; i++) if (recv_size[i]) { nprocs_recv++; }
    nprocs_send = 0;
    for (i=0; i<nprocs; i++) if (send_size[i]) { nprocs_send++; }

  /* receiver side data structures */
    rdispls = (int *) ADIOI_Malloc( nprocs * sizeof(int) );
    rtail = 0;
    for (i=0; i<nprocs; i++) { rdispls[i] = rtail; rtail += recv_size[i]; }

        /* data buffer */
    all_recv_buf = (char *) ADIOI_Malloc( rtail );

  /* sender side data structures */
    sdispls = (int *) ADIOI_Malloc( nprocs * sizeof(int) );
    stail = 0;
    for (i=0; i<nprocs; i++) { sdispls[i] = stail; stail += send_size[i]; }

        /* data buffer */
    all_send_buf = (char *) ADIOI_Malloc( stail );
    if (buftype_is_contig) {
	for (i=0; i<nprocs; i++)
	{
	    if (send_size[i]) {
		sbuf_ptr = all_send_buf + sdispls[i];
		memcpy( sbuf_ptr, buf + buf_idx[i], send_size[i] );
		buf_idx[i] += send_size[i];
	    }
	}
    } else {
	send_buf = (char **) ADIOI_Malloc( nprocs * sizeof(char *) );
	for (i=0; i<nprocs; i++)
	    send_buf[i] = all_send_buf + sdispls[i];
	ADIOI_Fill_send_buffer_nosend(fd, buf, flat_buf, send_buf,
                           offset_list, len_list, send_size,
			   send_req,
                           sent_to_proc, nprocs, myrank,
                           contig_access_count,
                           min_st_offset, fd_size, fd_start, fd_end,
                           send_buf_idx, curr_to_proc, done_to_proc, iter,
                           buftype_extent);
	ADIOI_Free(send_buf);
    }

    gpfsmpio_prof_cw[GPFSMPIO_CIO_T_DEXCH_SETUP] += MPI_Wtime() - io_time;

    io_time = MPI_Wtime();
  /* alltoallv */
    MPI_Alltoallv(
            all_send_buf, send_size, sdispls, MPI_BYTE,
            all_recv_buf, recv_size, rdispls, MPI_BYTE,
            fd->comm );

    ADIOI_Free( all_send_buf );
    ADIOI_Free(sdispls);

    gpfsmpio_prof_cw[GPFSMPIO_CIO_T_DEXCH_NET] += MPI_Wtime() - io_time;
    io_time = MPI_Wtime();
  /* data sieving pre-read */
  /* To avoid a read-modify-write, check if there are holes in the
     data to be written. For this, merge the (sorted) offset lists
     others_req using a heap-merge. */

    sum = 0;
    for (i=0; i<nprocs; i++) sum += count[i];
    srt_off = (ADIO_Offset *) ADIOI_Malloc((sum+1)*sizeof(ADIO_Offset));
    srt_len = (int *) ADIOI_Malloc((sum+1)*sizeof(int));

    ADIOI_Heap_merge(others_req, count, srt_off, srt_len, start_pos,
                     nprocs, nprocs_recv, sum);

    /* check if there are any holes */
    *hole = 0;
    /* See if there are holes before the first request or after the last request*/
    if((srt_off[0] > off) ||
       ((srt_off[sum-1] + srt_len[sum-1]) < (off + size)))
    {
       *hole = 1;
    }
    else /* See if there are holes between the requests, if there are more than one */
      for (i=0; i<sum-1; i++)
        if (srt_off[i]+srt_len[i] < srt_off[i+1]) {
            *hole = 1;
            break;
        }

    ADIOI_Free(srt_off);
    ADIOI_Free(srt_len);

    gpfsmpio_prof_cw[GPFSMPIO_CIO_T_DEXCH_SORT] += MPI_Wtime() - io_time;
    io_time = MPI_Wtime();
    if (nprocs_recv) {
        if (*hole) {
            ADIO_ReadContig(fd, write_buf, size, MPI_BYTE,
                            ADIO_EXPLICIT_OFFSET, off, &status, &err);
            /* --BEGIN ERROR HANDLING-- */
            if (err != MPI_SUCCESS) {
                *error_code = MPIO_Err_create_code(err,
                                                   MPIR_ERR_RECOVERABLE, myname,
                                                   __LINE__, MPI_ERR_IO,
                                                   "**ioRMWrdwr", 0);
                return;
            }
            /* --END ERROR HANDLING-- */
        }
    }
    gpfsmpio_prof_cw[GPFSMPIO_CIO_T_DEXCH_SIEVE] += MPI_Wtime() - io_time;

  /* scater all_recv_buf into 4M cb_buffer */
    tmp_len = (int *) ADIOI_Malloc(nprocs*sizeof(int));
    for (i=0; i<nprocs; i++)
    {
        if (recv_size[i]) {
            if (partial_recv[i]) {
                k = start_pos[i] + count[i] - 1;
                tmp_len[i] = others_req[i].lens[k];
                others_req[i].lens[k] = partial_recv[i];
            }

            sbuf_ptr = all_recv_buf + rdispls[i];
            for (j=0; j<count[i]; j++) {
                ADIOI_ENSURE_AINT_FITS_IN_PTR(others_req[i].mem_ptrs[ start_pos[i]+j ]);
                to_ptr = (char *) ADIOI_AINT_CAST_TO_VOID_PTR ( others_req[i].mem_ptrs[ start_pos[i]+j ] );
                len    =           others_req[i].lens[     start_pos[i]+j ]  ;
                memcpy( to_ptr, sbuf_ptr, len );
                sbuf_ptr += len;
            }

	    /* restore */
            if (partial_recv[i]) {
                k = start_pos[i] + count[i] - 1;
                others_req[i].lens[k] = tmp_len[i];
            }

        }
    }

    ADIOI_Free( tmp_len );
    ADIOI_Free( all_recv_buf );
    ADIOI_Free(rdispls);
    return;
}

static void ADIOI_Fill_send_buffer_nosend(ADIO_File fd, const void *buf, ADIOI_Flatlist_node
                           *flat_buf, char **send_buf, ADIO_Offset
                           *offset_list, ADIO_Offset *len_list, int *send_size,
                           MPI_Request *requests, int *sent_to_proc,
                           int nprocs, int myrank,
                           int contig_access_count,
                           ADIO_Offset min_st_offset, ADIO_Offset fd_size,
                           ADIO_Offset *fd_start, ADIO_Offset *fd_end,
                           int *send_buf_idx, int *curr_to_proc,
                           int *done_to_proc, int iter,
                           MPI_Aint buftype_extent)
{
/* this function is only called if buftype is not contig */

    int i, p, flat_buf_idx;
    ADIO_Offset flat_buf_sz, size_in_buf, buf_incr, size;
    int jj, n_buftypes;
    ADIO_Offset off, len, rem_len, user_buf_idx;

/*  curr_to_proc[p] = amount of data sent to proc. p that has already
    been accounted for so far
    done_to_proc[p] = amount of data already sent to proc. p in
    previous iterations
    user_buf_idx = current location in user buffer
    send_buf_idx[p] = current location in send_buf of proc. p  */

    for (i=0; i < nprocs; i++) {
	send_buf_idx[i] = curr_to_proc[i] = 0;
	done_to_proc[i] = sent_to_proc[i];
    }
    jj = 0;

    user_buf_idx = flat_buf->indices[0];
    flat_buf_idx = 0;
    n_buftypes = 0;
    flat_buf_sz = flat_buf->blocklens[0];

    /* flat_buf_idx = current index into flattened buftype
       flat_buf_sz = size of current contiguous component in
	                 flattened buf */

    for (i=0; i<contig_access_count; i++) {
	off     = offset_list[i];
	rem_len = len_list[i];

	/*this request may span the file domains of more than one process*/
  while (rem_len != 0) {
	    len = rem_len;
	    /* NOTE: len value is modified by ADIOI_Calc_aggregator() to be no
	     * longer than the single region that processor "p" is responsible
	     * for.
	     */
	    p = ADIOI_GPFS_Calc_aggregator(fd,
				      off,
				      min_st_offset,
				      &len,
				      fd_size,
				      fd_start,
				      fd_end);

	    if (send_buf_idx[p] < send_size[p]) {
		if (curr_to_proc[p]+len > done_to_proc[p]) {
		    if (done_to_proc[p] > curr_to_proc[p]) {
			size = ADIOI_MIN(curr_to_proc[p] + len -
                                done_to_proc[p], send_size[p]-send_buf_idx[p]);
			buf_incr = done_to_proc[p] - curr_to_proc[p];
			ADIOI_BUF_INCR
      ADIOI_Assert((curr_to_proc[p] + len - done_to_proc[p]) == (unsigned)(curr_to_proc[p] + len - done_to_proc[p]));
		        buf_incr = curr_to_proc[p] + len - done_to_proc[p];
      ADIOI_Assert((done_to_proc[p] + size) == (unsigned)(done_to_proc[p] + size));
			curr_to_proc[p] = done_to_proc[p] + size;
		        ADIOI_BUF_COPY
		    }
		    else {
			size = ADIOI_MIN(len,send_size[p]-send_buf_idx[p]);
			buf_incr = len;
      ADIOI_Assert((curr_to_proc[p] + size) == (unsigned)((ADIO_Offset)curr_to_proc[p] + size));
			curr_to_proc[p] += size;
			ADIOI_BUF_COPY
		    }
		    /* moved to alltoallv */
		    /*
		    if (send_buf_idx[p] == send_size[p]) {
			MPI_Isend(send_buf[p], send_size[p], MPI_BYTE, p,
				myrank+p+100*iter, fd->comm, requests+jj);
			jj++;
		    }
		    */
		}
		else {
        ADIOI_Assert((curr_to_proc[p] + len) == (unsigned)((ADIO_Offset)curr_to_proc[p] + len));
		    curr_to_proc[p] += (int)len;
		    buf_incr = len;
		    ADIOI_BUF_INCR
		}
	    }
	    else {
		buf_incr = len;
		ADIOI_BUF_INCR
            }
	    off     += len;
	    rem_len -= len;
	}
    }
    for (i=0; i < nprocs; i++)
	if (send_size[i]) sent_to_proc[i] = curr_to_proc[i];
}
