path: root/src/H5FDmpio.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * Copyright by the Board of Trustees of the University of Illinois.         *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the files COPYING and Copyright.html.  COPYING can be found at the root   *
 * of the source code distribution tree; Copyright.html can be found at the  *
 * root level of an installed copy of the electronic HDF5 document set and   *
 * is linked from the top-level documents page.  It can also be found at     *
 * http://hdfgroup.org/HDF5/doc/Copyright.html.  If you do not have          *
 * access to either file, you may request a copy from help@hdfgroup.org.     *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*
 * Programmer:  Robb Matzke <matzke@llnl.gov>
 *              Thursday, July 29, 1999
 *
 * Purpose:  This is the MPI-2 I/O driver.
 *
 */

/* Interface initialization */
#define H5_INTERFACE_INIT_FUNC  H5FD_mpio_init_interface


#include "H5private.h"    /* Generic Functions      */
#include "H5Dprivate.h"    /* Dataset functions      */
#include "H5Eprivate.h"    /* Error handling        */
#include "H5Fprivate.h"    /* File access        */
#include "H5FDprivate.h"  /* File drivers        */
#include "H5FDmpi.h"            /* MPI-based file drivers    */
#include "H5Iprivate.h"    /* IDs            */
#include "H5MMprivate.h"  /* Memory management      */
#include "H5Pprivate.h"         /* Property lists                       */

#ifdef H5_HAVE_PARALLEL

/*
 * The driver identification number, initialized at runtime if H5_HAVE_PARALLEL
 * is defined. This allows applications to still have the H5FD_MPIO
 * "constants" in their source code.
 */
static hid_t H5FD_MPIO_g = 0;

/*
 * The view is set to this value
 */
static char H5FD_mpi_native_g[] = "native";

/*
 * The description of a file belonging to this driver.
 * The EOF value is only used just after the file is opened in order for the
 * library to determine whether the file is empty, truncated, or okay. The MPIO
 * driver doesn't bother to keep it updated since it's an expensive operation.
 */
typedef struct H5FD_mpio_t {
    H5FD_t  pub;    /*public stuff, must be first    */
    MPI_File  f;    /*MPIO file handle      */
    MPI_Comm  comm;    /*communicator        */
    MPI_Info  info;    /*file information      */
    int         mpi_rank;       /* This process's rank                  */
    int         mpi_size;       /* Total number of processes            */
    haddr_t  eof;    /*end-of-file marker      */
    haddr_t  eoa;    /*end-of-address marker      */
    haddr_t  last_eoa;  /* Last known end-of-address marker  */
} H5FD_mpio_t;

/* Private Prototypes */

/* Callbacks */
static void *H5FD_mpio_fapl_get(H5FD_t *_file);
static void *H5FD_mpio_fapl_copy(const void *_old_fa);
static herr_t H5FD_mpio_fapl_free(void *_fa);
static H5FD_t *H5FD_mpio_open(const char *name, unsigned flags, hid_t fapl_id,
            haddr_t maxaddr);
static herr_t H5FD_mpio_close(H5FD_t *_file);
static herr_t H5FD_mpio_query(const H5FD_t *_f1, unsigned long *flags);
static haddr_t H5FD_mpio_get_eoa(const H5FD_t *_file, H5FD_mem_t type);
static herr_t H5FD_mpio_set_eoa(H5FD_t *_file, H5FD_mem_t type, haddr_t addr);
static haddr_t H5FD_mpio_get_eof(const H5FD_t *_file);
static herr_t  H5FD_mpio_get_handle(H5FD_t *_file, hid_t fapl, void** file_handle);
static herr_t H5FD_mpio_read(H5FD_t *_file, H5FD_mem_t type, hid_t dxpl_id, haddr_t addr,
            size_t size, void *buf);
static herr_t H5FD_mpio_write(H5FD_t *_file, H5FD_mem_t type, hid_t dxpl_id, haddr_t addr,
            size_t size, const void *buf);
static herr_t H5FD_mpio_flush(H5FD_t *_file, hid_t dxpl_id, unsigned closing);
static herr_t H5FD_mpio_truncate(H5FD_t *_file, hid_t dxpl_id, hbool_t closing);
static int H5FD_mpio_mpi_rank(const H5FD_t *_file);
static int H5FD_mpio_mpi_size(const H5FD_t *_file);
static MPI_Comm H5FD_mpio_communicator(const H5FD_t *_file);

/* MPIO-specific file access properties */
typedef struct H5FD_mpio_fapl_t {
    MPI_Comm    comm;    /*communicator      */
    MPI_Info    info;    /*file information    */
} H5FD_mpio_fapl_t;

/* The MPIO file driver information */
static const H5FD_class_mpi_t H5FD_mpio_g = {
    {   /* Start of superclass information */
    "mpio",          /*name      */
    HADDR_MAX,          /*maxaddr    */
    H5F_CLOSE_SEMI,        /* fc_degree    */
    NULL,          /*sb_size    */
    NULL,          /*sb_encode    */
    NULL,          /*sb_decode    */
    sizeof(H5FD_mpio_fapl_t),      /*fapl_size    */
    H5FD_mpio_fapl_get,        /*fapl_get    */
    H5FD_mpio_fapl_copy,      /*fapl_copy    */
    H5FD_mpio_fapl_free,       /*fapl_free    */
    0,                        /*dxpl_size    */
    NULL,          /*dxpl_copy    */
    NULL,          /*dxpl_free    */
    H5FD_mpio_open,        /*open      */
    H5FD_mpio_close,        /*close      */
    NULL,          /*cmp      */
    H5FD_mpio_query,                    /*query      */
    NULL,          /*get_type_map    */
    NULL,          /*alloc      */
    NULL,          /*free      */
    H5FD_mpio_get_eoa,        /*get_eoa    */
    H5FD_mpio_set_eoa,         /*set_eoa    */
    H5FD_mpio_get_eof,        /*get_eof    */
    H5FD_mpio_get_handle,                       /*get_handle            */
    H5FD_mpio_read,        /*read      */
    H5FD_mpio_write,        /*write      */
    H5FD_mpio_flush,        /*flush      */
    H5FD_mpio_truncate,        /*truncate    */
    NULL,                                       /*lock                  */
    NULL,                                       /*unlock                */
    H5FD_FLMAP_DICHOTOMY                        /*fl_map                */
    },  /* End of superclass information */
    H5FD_mpio_mpi_rank,                         /*get_rank              */
    H5FD_mpio_mpi_size,                         /*get_size              */
    H5FD_mpio_communicator                      /*get_comm              */
};

#ifdef H5FDmpio_DEBUG
/* Flags to control debug actions in H5Fmpio.
 * Meant to be indexed by characters.
 *
 * 'c' show result of MPI_Get_count after read
 * 'r' show read offset and size
 * 't' trace function entry and exit
 * 'w' show write offset and size
 */
static int H5FD_mpio_Debug[256] =
        { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 };
#endif


/*--------------------------------------------------------------------------
NAME
   H5FD_mpio_init_interface -- Initialize interface-specific information
USAGE
    herr_t H5FD_mpio_init_interface()

RETURNS
    Non-negative on success/Negative on failure
DESCRIPTION
    Initializes any interface-specific data or routines.  (Just calls
    H5FD_mpio_init currently).

--------------------------------------------------------------------------*/
static herr_t
H5FD_mpio_init_interface(void)
{
    FUNC_ENTER_NOAPI_NOINIT_NOERR

    FUNC_LEAVE_NOAPI(H5FD_mpio_init())
} /* H5FD_mpio_init_interface() */


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_init
 *
 * Purpose:  Initialize this driver by registering the driver with the
 *    library.
 *
 * Return:  Success:  The driver ID for the mpio driver.
 *
 *    Failure:  Negative.
 *
 * Programmer:  Robb Matzke
 *              Thursday, August 5, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
hid_t
H5FD_mpio_init(void)
{
#ifdef H5FDmpio_DEBUG
    static int H5FD_mpio_Debug_inited=0;
#endif /* H5FDmpio_DEBUG */
    hid_t ret_value;          /* Return value */

    FUNC_ENTER_NOAPI(FAIL)

    if (H5I_VFL!=H5I_get_type(H5FD_MPIO_g))
        H5FD_MPIO_g = H5FD_register((const H5FD_class_t *)&H5FD_mpio_g,sizeof(H5FD_class_mpi_t),FALSE);

#ifdef H5FDmpio_DEBUG
    if (!H5FD_mpio_Debug_inited)
    {
  /* set debug mask */
  /* Should this be done in H5F global initialization instead of here? */
        const char *s = HDgetenv ("H5FD_mpio_Debug");
        if (s) {
      while (*s){
    H5FD_mpio_Debug[(int)*s]++;
    s++;
      }
        }
  H5FD_mpio_Debug_inited++;
    }
#endif /* H5FDmpio_DEBUG */

    /* Set return value */
    ret_value=H5FD_MPIO_g;

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*---------------------------------------------------------------------------
 * Function:  H5FD_mpio_term
 *
 * Purpose:  Shut down the VFD
 *
 * Return:  <none>
 *
 * Programmer:  Quincey Koziol
 *              Friday, Jan 30, 2004
 *
 * Modification:
 *
 *---------------------------------------------------------------------------
 */
void
H5FD_mpio_term(void)
{
    FUNC_ENTER_NOAPI_NOINIT_NOERR

    /* Reset VFL ID */
    H5FD_MPIO_g=0;

    FUNC_LEAVE_NOAPI_VOID
} /* end H5FD_mpio_term() */


/*-------------------------------------------------------------------------
 * Function:  H5Pset_fapl_mpio
 *
 * Purpose:  Store the user supplied MPIO communicator comm and info in
 *    the file access property list FAPL_ID which can then be used
 *    to create and/or open the file.  This function is available
 *    only in the parallel HDF5 library and is not collective.
 *
 *    comm is the MPI communicator to be used for file open as
 *    defined in MPI_FILE_OPEN of MPI-2. This function makes a
 *    duplicate of comm. Any modification to comm after this function
 *    call returns has no effect on the access property list.
 *
 *    info is the MPI Info object to be used for file open as
 *    defined in MPI_FILE_OPEN of MPI-2. This function makes a
 *    duplicate of info. Any modification to info after this
 *    function call returns has no effect on the access property
 *    list.
 *
 *              If fapl_id has previously set comm and info values, they
 *              will be replaced and the old communicator and Info object
 *              are freed.
 *
 * Return:  Success:  Non-negative
 *
 *     Failure:  Negative
 *
 * Programmer:  Albert Cheng
 *    Feb 3, 1998
 *
 * Modifications:
 *    Robb Matzke, 1998-02-18
 *    Check all arguments before the property list is updated so we
 *    don't leave the property list in a bad state if something
 *    goes wrong.  Also, the property list data type changed to
 *    allow more generality so all the mpi-related stuff is in the
 *    `u.mpi' member.  The `access_mode' will contain only
 *     mpi-related flags defined in H5Fpublic.h.
 *
 *    Albert Cheng, 1998-04-16
 *    Removed the ACCESS_MODE argument.  The access mode is changed
 *    to be controlled by data transfer property list during data
 *    read/write calls.
 *
 *     Robb Matzke, 1999-08-06
 *    Modified to work with the virtual file layer.
 *
 *    Raymond Lu, 2001-10-23
 *    Changed the file access list to the new generic property
 *    list.
 *
 *    Albert Cheng, 2003-04-17
 *    Modified the description of the function that it now stores
 *    a duplicate of the communicator and INFO object.  Free the
 *    old duplicates if previously set.  (Work is actually done
 *    by H5P_set_driver.)
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_fapl_mpio(hid_t fapl_id, MPI_Comm comm, MPI_Info info)
{
    H5FD_mpio_fapl_t  fa;
    H5P_genplist_t *plist;      /* Property list pointer */
    herr_t ret_value;

    FUNC_ENTER_API(FAIL)
    H5TRACE3("e", "iMcMi", fapl_id, comm, info);

    if(fapl_id == H5P_DEFAULT)
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "can't set values in default property list")

    /* Check arguments */
    if(NULL == (plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a file access list")
    if(MPI_COMM_NULL == comm)
  HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a valid communicator")

    /* Initialize driver specific properties */
    fa.comm = comm;
    fa.info = info;

    /* duplication is done during driver setting. */
    ret_value= H5P_set_driver(plist, H5FD_MPIO, &fa);

done:
    FUNC_LEAVE_API(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:  H5Pget_fapl_mpio
 *
 * Purpose:  If the file access property list is set to the H5FD_MPIO
 *    driver then this function returns duplicates of the MPI
 *    communicator and Info object stored through the comm and
 *    info pointers.  It is the responsibility of the application
 *    to free the returned communicator and Info object.
 *
 * Return:  Success:  Non-negative with the communicator and
 *        Info object returned through the comm and
 *        info arguments if non-null. Since they are
 *        duplicates of the stored objects, future
 *        modifications to the access property list do
 *        not affect them and it is the responsibility
 *        of the application to free them.
 *
 *     Failure:  Negative
 *
 * Programmer:  Robb Matzke
 *    Thursday, February 26, 1998
 *
 * Modifications:
 *
 *          Albert Cheng, Apr 16, 1998
 *          Removed the access_mode argument.  The access_mode is changed
 *          to be controlled by data transfer property list during data
 *          read/write calls.
 *
 *    Raymond Lu, 2001-10-23
 *    Changed the file access list to the new generic property
 *    list.
 *
 *    Albert Cheng, 2003-04-17
 *    Return duplicates of the stored communicator and Info object.
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pget_fapl_mpio(hid_t fapl_id, MPI_Comm *comm/*out*/, MPI_Info *info/*out*/)
{
    H5FD_mpio_fapl_t  *fa;
    H5P_genplist_t *plist;      /* Property list pointer */
    MPI_Comm  comm_tmp=MPI_COMM_NULL;
    int    mpi_code;    /* mpi return code */
    herr_t      ret_value=SUCCEED;      /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE3("e", "ixx", fapl_id, comm, info);

    if(NULL == (plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a file access list")
    if(H5FD_MPIO != H5P_get_driver(plist))
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "incorrect VFL driver")
    if(NULL == (fa = (H5FD_mpio_fapl_t *)H5P_get_driver_info(plist)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "bad VFL driver info")

    /* Store the duplicated communicator in a temporary variable for error */
    /* recovery in case the INFO duplication fails.  We cannot attempt to */
    /* the value into *comm yet since if MPI_Comm_dup fails, we will end  */
    /* up freeing whatever *comm holds and that could be invalid. */
    if (comm){
  if (MPI_SUCCESS != (mpi_code=MPI_Comm_dup(fa->comm, &comm_tmp)))
      HMPI_GOTO_ERROR(FAIL, "MPI_Comm_dup failed", mpi_code)
    }

    if (info){
  if (MPI_INFO_NULL != fa->info){
      if (MPI_SUCCESS != (mpi_code=MPI_Info_dup(fa->info, info)))
    HMPI_GOTO_ERROR(FAIL, "MPI_Info_dup failed", mpi_code)
  }else{
      /* do not dup it */
      *info = MPI_INFO_NULL;
  }
    }

    if (comm)
        *comm = comm_tmp;

done:
    if (FAIL==ret_value){
  /* need to free anything created here */
  if (comm_tmp != MPI_COMM_NULL)
      MPI_Comm_free(&comm_tmp);
    }
    FUNC_LEAVE_API(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:  H5Pset_dxpl_mpio
 *
 * Purpose:  Set the data transfer property list DXPL_ID to use transfer
 *    mode XFER_MODE. The property list can then be used to control
 *    the I/O transfer mode during data I/O operations. The valid
 *    transfer modes are:
 *
 *     H5FD_MPIO_INDEPENDENT:
 *      Use independent I/O access (the default).
 *
 *     H5FD_MPIO_COLLECTIVE:
 *      Use collective I/O access.
 *
 * Return:  Success:  Non-negative
 *     Failure:  Negative
 *
 * Programmer:  Albert Cheng
 *    April 2, 1998
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_dxpl_mpio(hid_t dxpl_id, H5FD_mpio_xfer_t xfer_mode)
{
    H5P_genplist_t *plist;      /* Property list pointer */
    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE2("e", "iDt", dxpl_id, xfer_mode);

    if(dxpl_id == H5P_DEFAULT)
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "can't set values in default property list")

    /* Check arguments */
    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")
    if(H5FD_MPIO_INDEPENDENT != xfer_mode && H5FD_MPIO_COLLECTIVE != xfer_mode)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "incorrect xfer_mode")

    /* Set the transfer mode */
    if(H5P_set(plist, H5D_XFER_IO_XFER_MODE_NAME, &xfer_mode) < 0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Pset_dxpl_mpio() */


/*-------------------------------------------------------------------------
 * Function:  H5Pget_dxpl_mpio
 *
 * Purpose:  Queries the transfer mode current set in the data transfer
 *    property list DXPL_ID. This is not collective.
 *
 * Return:  Success:  Non-negative, with the transfer mode returned
 *        through the XFER_MODE argument if it is
 *        non-null.
 *
 *     Failure:  Negative
 *
 * Programmer:  Albert Cheng
 *    April 2, 1998
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pget_dxpl_mpio(hid_t dxpl_id, H5FD_mpio_xfer_t *xfer_mode/*out*/)
{
    H5P_genplist_t *plist;              /* Property list pointer */
    herr_t      ret_value = SUCCEED;    /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE2("e", "ix", dxpl_id, xfer_mode);

    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")

    /* Get the transfer mode */
    if(xfer_mode)
        if(H5P_get(plist, H5D_XFER_IO_XFER_MODE_NAME, xfer_mode) < 0)
            HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to get value")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Pget_dxpl_mpio() */


/*-------------------------------------------------------------------------
 * Function:  H5Pset_dxpl_mpio_collective_opt
 *
 * Purpose:	To set a flag to choose linked chunk I/O or multi-chunk I/O
 *		without involving decision-making inside HDF5
 *
 * Note:	The library will do linked chunk I/O or multi-chunk I/O without
 *		involving communications for decision-making process.
 *		The library won't behave as it asks for only when we find
 *		that the low-level MPI-IO package doesn't support this.
 *
 * Return:	Success:	Non-negative
 * 		Failure:	Negative
 *
 * Programmer:	Kent Yang
 *		? ?, ?
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_dxpl_mpio_collective_opt(hid_t dxpl_id, H5FD_mpio_collective_opt_t opt_mode)
{
    H5P_genplist_t *plist;      /* Property list pointer */
    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE2("e", "iDc", dxpl_id, opt_mode);

    if(dxpl_id == H5P_DEFAULT)
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "can't set values in default property list")

    /* Check arguments */
    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")

    /* Set the transfer mode */
    if(H5P_set(plist, H5D_XFER_MPIO_COLLECTIVE_OPT_NAME, &opt_mode) < 0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Pset_dxpl_mpio_collective_opt() */


/*-------------------------------------------------------------------------
 * Function:  H5Pset_dxpl_mpio_chunk_opt
 *
 * Purpose:	To set a flag to choose linked chunk I/O or multi-chunk I/O
 *		without involving decision-making inside HDF5
 *
 * Note:	The library will do linked chunk I/O or multi-chunk I/O without
 *		involving communications for decision-making process.
 *		The library won't behave as it asks for only when we find
 *		that the low-level MPI-IO package doesn't support this.
 *
 * Return:	Success:	Non-negative
 * 		Failure:	Negative
 *
 * Programmer:	Kent Yang
 *		? ?, ?
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_dxpl_mpio_chunk_opt(hid_t dxpl_id, H5FD_mpio_chunk_opt_t opt_mode)
{
    H5P_genplist_t *plist;      /* Property list pointer */
    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE2("e", "iDh", dxpl_id, opt_mode);

    if(dxpl_id == H5P_DEFAULT)
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "can't set values in default property list")

    /* Check arguments */
    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")

    /* Set the transfer mode */
    if(H5P_set(plist, H5D_XFER_MPIO_CHUNK_OPT_HARD_NAME, &opt_mode) < 0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Pset_dxpl_mpio_chunk_opt() */


/*-------------------------------------------------------------------------
 * Function:  H5Pset_dxpl_mpio_chunk_opt_num
 *
 * Purpose:	To set a threshold for doing linked chunk IO
 *
 * Note:	If the number is greater than the threshold set by the user,
 *		the library will do linked chunk I/O; otherwise, I/O will be
 *		done for every chunk.
 *
 * Return:	Success:	Non-negative
 * 		Failure:	Negative
 *
 * Programmer:	Kent Yang
 *		? ?, ?
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_dxpl_mpio_chunk_opt_num(hid_t dxpl_id, unsigned num_chunk_per_proc)
{
    H5P_genplist_t *plist;      /* Property list pointer */
    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE2("e", "iIu", dxpl_id, num_chunk_per_proc);

    if(dxpl_id == H5P_DEFAULT)
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "can't set values in default property list")

    /* Check arguments */
    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")

    /* Set the transfer mode */
    if(H5P_set(plist, H5D_XFER_MPIO_CHUNK_OPT_NUM_NAME, &num_chunk_per_proc) < 0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Pset_dxpl_mpio_chunk_opt_num() */


/*-------------------------------------------------------------------------
 * Function:  H5Pset_dxpl_mpio_chunk_opt_ratio
 *
 * Purpose:	To set a threshold for doing collective I/O for each chunk
 *
 * Note:	The library will calculate the percentage of the number of
 *		process holding selections at each chunk. If that percentage
 *		of number of process in the individual chunk is greater than
 *		the threshold set by the user, the library will do collective
 *		chunk I/O for this chunk; otherwise, independent I/O will be
 *		done for this chunk.
 *
 * Return:	Success:	Non-negative
 * 		Failure:	Negative
 *
 * Programmer:	Kent Yang
 *		? ?, ?
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5Pset_dxpl_mpio_chunk_opt_ratio(hid_t dxpl_id, unsigned percent_num_proc_per_chunk)
{
    H5P_genplist_t *plist;      /* Property list pointer */
    herr_t ret_value = SUCCEED; /* Return value */

    FUNC_ENTER_API(FAIL)
    H5TRACE2("e", "iIu", dxpl_id, percent_num_proc_per_chunk);

    if(dxpl_id == H5P_DEFAULT)
        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "can't set values in default property list")

    /* Check arguments */
    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")

    /* Set the transfer mode */
    if(H5P_set(plist, H5D_XFER_MPIO_CHUNK_OPT_RATIO_NAME, &percent_num_proc_per_chunk) < 0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")

done:
    FUNC_LEAVE_API(ret_value)
} /* end H5Pset_dxpl_mpio_chunk_opt_ratio() */


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_fapl_get
 *
 * Purpose:  Returns a file access property list which could be used to
 *    create another file the same as this one.
 *
 * Return:  Success:  Ptr to new file access property list with all
 *        fields copied from the file pointer.
 *
 *    Failure:  NULL
 *
 * Programmer:  Robb Matzke
 *              Friday, August 13, 1999
 *
 *-------------------------------------------------------------------------
 */
static void *
H5FD_mpio_fapl_get(H5FD_t *_file)
{
    H5FD_mpio_t    *file = (H5FD_mpio_t*)_file;
    H5FD_mpio_fapl_t  *fa = NULL;
    void      *ret_value;       /* Return value */

    FUNC_ENTER_NOAPI_NOINIT

    HDassert(file);
    HDassert(H5FD_MPIO == file->pub.driver_id);

    if(NULL == (fa = (H5FD_mpio_fapl_t *)H5MM_calloc(sizeof(H5FD_mpio_fapl_t))))
        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")

    /* Duplicate communicator and Info object. */
    if(FAIL == H5FD_mpi_comm_info_dup(file->comm, file->info, &fa->comm, &fa->info))
  HGOTO_ERROR(H5E_INTERNAL, H5E_CANTCOPY, NULL, "Communicator/Info duplicate failed")

    /* Set return value */
    ret_value = fa;

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_fapl_copy
 *
 * Purpose:  Copies the mpio-specific file access properties.
 *
 * Return:  Success:  Ptr to a new property list
 *
 *    Failure:  NULL
 *
 * Programmer:  Albert Cheng
 *              Jan  8, 2003
 *
 *-------------------------------------------------------------------------
 */
static void *
H5FD_mpio_fapl_copy(const void *_old_fa)
{
    void    *ret_value = NULL;
    const H5FD_mpio_fapl_t *old_fa = (const H5FD_mpio_fapl_t*)_old_fa;
    H5FD_mpio_fapl_t  *new_fa = NULL;

    FUNC_ENTER_NOAPI_NOINIT
#ifdef H5FDmpio_DEBUG
if (H5FD_mpio_Debug[(int)'t'])
fprintf(stderr, "enter H5FD_mpio_fapl_copy\n");
#endif

    if(NULL == (new_fa = (H5FD_mpio_fapl_t *)H5MM_malloc(sizeof(H5FD_mpio_fapl_t))))
        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")

    /* Copy the general information */
    HDmemcpy(new_fa, old_fa, sizeof(H5FD_mpio_fapl_t));

    /* Duplicate communicator and Info object. */
    if(FAIL == H5FD_mpi_comm_info_dup(old_fa->comm, old_fa->info, &new_fa->comm, &new_fa->info))
  HGOTO_ERROR(H5E_INTERNAL, H5E_CANTCOPY, NULL, "Communicator/Info duplicate failed")
    ret_value = new_fa;

done:
    if (NULL == ret_value){
  /* cleanup */
  if (new_fa)
      H5MM_xfree(new_fa);
    }

#ifdef H5FDmpio_DEBUG
if (H5FD_mpio_Debug[(int)'t'])
fprintf(stderr, "leaving H5FD_mpio_fapl_copy\n");
#endif
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD_mpio_fapl_copy() */


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_fapl_free
 *
 * Purpose:  Frees the mpio-specific file access properties.
 *
 * Return:  Success:  0
 *
 *    Failure:  -1
 *
 * Programmer:  Albert Cheng
 *              Jan  8, 2003
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_fapl_free(void *_fa)
{
    herr_t    ret_value = SUCCEED;
    H5FD_mpio_fapl_t  *fa = (H5FD_mpio_fapl_t*)_fa;

    FUNC_ENTER_NOAPI_NOINIT_NOERR
#ifdef H5FDmpio_DEBUG
if (H5FD_mpio_Debug[(int)'t'])
fprintf(stderr, "in H5FD_mpio_fapl_free\n");
#endif
    HDassert(fa);

    /* Free the internal communicator and INFO object */
    HDassert(MPI_COMM_NULL!=fa->comm);
    H5FD_mpi_comm_info_free(&fa->comm, &fa->info);
    H5MM_xfree(fa);

#ifdef H5FDmpio_DEBUG
if (H5FD_mpio_Debug[(int)'t'])
fprintf(stderr, "leaving H5FD_mpio_fapl_free\n");
#endif
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD_mpio_fapl_free() */


/*-------------------------------------------------------------------------
 * Function:	H5FD_set_mpio_atomicity
 *
 * Purpose:	Sets the atomicity mode
 *
 * Return:	Success:	Non-negative
 *
 * 		Failure:	Negative
 *
 * Programmer:	Mohamad Chaarawi
 *		Feb 14, 2012
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5FD_set_mpio_atomicity(H5FD_t *_file, hbool_t flag)
{
    H5FD_mpio_t *file = (H5FD_mpio_t*)_file;
    int          mpi_code;               /* MPI return code */
    int          temp_flag;
    herr_t       ret_value = SUCCEED;

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
    	fprintf(stdout, "Entering H5FD_set_mpio_atomicity\n");
#endif

    if (FALSE == flag)
        temp_flag = 0;
    else
        temp_flag = 1;

    /* set atomicity value */
    if (MPI_SUCCESS != (mpi_code=MPI_File_set_atomicity(file->f, temp_flag)))
        HMPI_GOTO_ERROR(FAIL, "MPI_File_set_atomicity", mpi_code)

done:
#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
    	fprintf(stdout, "Leaving H5FD_set_mpio_atomicity\n");
#endif
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:	H5FD_get_mpio_atomicity
 *
 * Purpose:	Returns the atomicity mode
 *
 * Return:	Success:	Non-negative
 *
 * 		Failure:	Negative
 *
 * Programmer:	Mohamad Chaarawi
 *		Feb 14, 2012
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5FD_get_mpio_atomicity(H5FD_t *_file, hbool_t *flag)
{
    H5FD_mpio_t *file = (H5FD_mpio_t*)_file;
    int          mpi_code;               /* MPI return code */
    int          temp_flag;
    herr_t       ret_value = SUCCEED;

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
    	fprintf(stdout, "Entering H5FD_get_mpio_atomicity\n");
#endif

    /* get atomicity value */
    if (MPI_SUCCESS != (mpi_code=MPI_File_get_atomicity(file->f, &temp_flag)))
        HMPI_GOTO_ERROR(FAIL, "MPI_File_get_atomicity", mpi_code)

    if (0 != temp_flag)
        *flag = TRUE;
    else
        *flag = FALSE;

done:
#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
    	fprintf(stdout, "Leaving H5FD_get_mpio_atomicity\n");
#endif
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5FD_mpio_open
 *
 * Purpose:     Opens a file with name NAME.  The FLAGS are a bit field with
 *    purpose similar to the second argument of open(2) and which
 *    are defined in H5Fpublic.h. The file access property list
 *    FAPL_ID contains the properties driver properties and MAXADDR
 *    is the largest address which this file will be expected to
 *    access.  This is collective.
 *
 * Return:      Success:        A new file pointer.
 *
 *              Failure:        NULL
 *
 * Programmer:
 *              January 30, 1998
 *
 * Modifications:
 *     Robb Matzke, 1998-02-18
 *    Added the ACCESS_PARMS argument.  Moved some error checking
 *    here from elsewhere.
 *
 *        rky, 1998-01-11
 *        Added H5FD_mpio_Debug debug flags controlled by MPI_Info.
 *
 *        rky, 1998-08-28
 *    Init flag controlling redundant metadata writes to disk.
 *
 *        rky, 1998-12-07
 *    Added barrier after MPI_File_set_size to prevent race
 *    condition -- subsequent writes were being truncated, causing
 *    holes in file.
 *
 *     Robb Matzke, 1999-08-06
 *    Modified to work with the virtual file layer.
 *
 *        rky & ppw, 1999-11-07
 *    Modified "H5FD_mpio_open" so that file-truncation is
 *              avoided for brand-new files (with zero filesize).
 *
 *     Albert Cheng, 2003-04-17
 *     Duplicate the communicator and Info object so that file is
 *     insulated from the old one.
 *-------------------------------------------------------------------------
 */
static H5FD_t *
H5FD_mpio_open(const char *name, unsigned flags, hid_t fapl_id,
         haddr_t UNUSED maxaddr)
{
    H5FD_mpio_t      *file=NULL;
    MPI_File      fh;
    unsigned                    file_opened=0;  /* Flag to indicate that the file was successfully opened */
    int        mpi_amode;
    int        mpi_rank;       /* MPI rank of this process */
    int        mpi_size;       /* Total number of MPI processes */
    int        mpi_code;  /* mpi return code */
    MPI_Offset      size;
    const H5FD_mpio_fapl_t  *fa=NULL;
    H5FD_mpio_fapl_t    _fa;
    H5P_genplist_t *plist;      /* Property list pointer */
    MPI_Comm                    comm_dup=MPI_COMM_NULL;
    MPI_Info                    info_dup=MPI_INFO_NULL;
    H5FD_t      *ret_value;     /* Return value */
#ifndef H5_HAVE_MPI_GET_SIZE
    h5_stat_t                 stat_buf;
#endif

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t']) {
      fprintf(stdout, "Entering H5FD_mpio_open(name=\"%s\", flags=0x%x, "
    "fapl_id=%d, maxaddr=%lu)\n", name, flags, (int)fapl_id, (unsigned long)maxaddr);
    }
#endif

    /* Obtain a pointer to mpio-specific file access properties */
    if(NULL == (plist = H5P_object_verify(fapl_id, H5P_FILE_ACCESS)))
        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a file access property list")
    if(H5P_FILE_ACCESS_DEFAULT == fapl_id || H5FD_MPIO != H5P_get_driver(plist)) {
        _fa.comm = MPI_COMM_SELF; /*default*/
        _fa.info = MPI_INFO_NULL; /*default*/
        fa = &_fa;
    } else {
        if(NULL == (fa = (const H5FD_mpio_fapl_t *)H5P_get_driver_info(plist)))
	    HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, NULL, "bad VFL driver info")
    }

    /* Duplicate communicator and Info object for use by this file. */
    if (FAIL==H5FD_mpi_comm_info_dup(fa->comm, fa->info, &comm_dup, &info_dup))
        HGOTO_ERROR(H5E_INTERNAL, H5E_CANTCOPY, NULL, "Communicator/Info duplicate failed")

    /* convert HDF5 flags to MPI-IO flags */
    /* some combinations are illegal; let MPI-IO figure it out */
    mpi_amode  = (flags&H5F_ACC_RDWR) ? MPI_MODE_RDWR : MPI_MODE_RDONLY;
    if (flags&H5F_ACC_CREAT)  mpi_amode |= MPI_MODE_CREATE;
    if (flags&H5F_ACC_EXCL)  mpi_amode |= MPI_MODE_EXCL;

#ifdef H5FDmpio_DEBUG
    /* Check for debug commands in the info parameter */
    {
  char debug_str[128];
        int flag, i;
        if (MPI_INFO_NULL != info_dup) {
            /*OKAY: CAST DISCARDS CONST*/
            MPI_Info_get(fa->info, (char *)H5F_MPIO_DEBUG_KEY, 127, debug_str, &flag);
            if (flag) {
                fprintf(stdout, "H5FD_mpio debug flags=%s\n", debug_str );
                for (i=0;
                     debug_str[i]/*end of string*/ && i<128/*just in case*/;
                     ++i) {
                    H5FD_mpio_Debug[(int)debug_str[i]] = 1;
                }
            }
        }
    }
#endif

    /*OKAY: CAST DISCARDS CONST*/
    if(MPI_SUCCESS != (mpi_code = MPI_File_open(comm_dup, (char*)name, mpi_amode, info_dup, &fh)))
        HMPI_GOTO_ERROR(NULL, "MPI_File_open failed", mpi_code)
    file_opened=1;

    /* Get the MPI rank of this process and the total number of processes */
    if (MPI_SUCCESS != (mpi_code=MPI_Comm_rank (comm_dup, &mpi_rank)))
        HMPI_GOTO_ERROR(NULL, "MPI_Comm_rank failed", mpi_code)
    if (MPI_SUCCESS != (mpi_code=MPI_Comm_size (comm_dup, &mpi_size)))
        HMPI_GOTO_ERROR(NULL, "MPI_Comm_size failed", mpi_code)

    /* Build the return value and initialize it */
    if(NULL == (file = (H5FD_mpio_t *)H5MM_calloc(sizeof(H5FD_mpio_t))))
        HGOTO_ERROR(H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
    file->f = fh;
    file->comm = comm_dup;
    file->info = info_dup;
    file->mpi_rank = mpi_rank;
    file->mpi_size = mpi_size;

    /* Only processor p0 will get the filesize and broadcast it. */
    if (mpi_rank == 0) {
        /* Get current file size.  If MPI_File_get_size is disabled in configuration
         * because it doesn't return correct value (SGI Altix Propack 4),
         * use stat to get the file size. */
#ifdef H5_HAVE_MPI_GET_SIZE
        if (MPI_SUCCESS != (mpi_code=MPI_File_get_size(fh, &size)))
            HMPI_GOTO_ERROR(NULL, "MPI_File_get_size failed", mpi_code)
#else
        if((mpi_code=HDstat(name, &stat_buf))<0)
            HMPI_GOTO_ERROR(NULL, "stat failed", mpi_code)
        /* Hopefully this casting is safe */
        size = (MPI_Offset)(stat_buf.st_size);
#endif
    } /* end if */

    /* Broadcast file size */
    if(MPI_SUCCESS != (mpi_code = MPI_Bcast(&size, (int)sizeof(MPI_Offset), MPI_BYTE, 0, comm_dup)))
        HMPI_GOTO_ERROR(NULL, "MPI_Bcast failed", mpi_code)

    /* Determine if the file should be truncated */
    if(size && (flags & H5F_ACC_TRUNC)) {
        if (MPI_SUCCESS != (mpi_code=MPI_File_set_size(fh, (MPI_Offset)0)))
            HMPI_GOTO_ERROR(NULL, "MPI_File_set_size failed", mpi_code)

        /* Don't let any proc return until all have truncated the file. */
        if (MPI_SUCCESS!= (mpi_code=MPI_Barrier(comm_dup)))
            HMPI_GOTO_ERROR(NULL, "MPI_Barrier failed", mpi_code)

        /* File is zero size now */
        size = 0;
    } /* end if */

    /* Set the size of the file (from library's perspective) */
    file->eof = H5FD_mpi_MPIOff_to_haddr(size);

    /* Set return value */
    ret_value=(H5FD_t*)file;

done:
    if(ret_value==NULL) {
        if(file_opened)
            MPI_File_close(&fh);
  if (MPI_COMM_NULL != comm_dup)
      MPI_Comm_free(&comm_dup);
  if (MPI_INFO_NULL != info_dup)
      MPI_Info_free(&info_dup);
  if (file)
      H5MM_xfree(file);
    } /* end if */

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
        fprintf(stdout, "Leaving H5FD_mpio_open\n" );
#endif
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5FD_mpio_close
 *
 * Purpose:     Closes a file.  This is collective.
 *
 * Return:      Success:  Non-negative
 *
 *     Failure:  Negative
 *
 * Programmer:  Unknown
 *              January 30, 1998
 *
 * Modifications:
 *     Robb Matzke, 1998-02-18
 *    Added the ACCESS_PARMS argument.
 *
 *     Robb Matzke, 1999-08-06
 *    Modified to work with the virtual file layer.
 *
 *     Albert Cheng, 2003-04-17
 *    Free the communicator stored.
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_close(H5FD_t *_file)
{
    H5FD_mpio_t  *file = (H5FD_mpio_t*)_file;
    int    mpi_code;          /* MPI return code */
    herr_t      ret_value=SUCCEED;      /* Return value */

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
      fprintf(stdout, "Entering H5FD_mpio_close\n");
#endif
    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);

    /* MPI_File_close sets argument to MPI_FILE_NULL */
    if (MPI_SUCCESS != (mpi_code=MPI_File_close(&(file->f)/*in,out*/)))
        HMPI_GOTO_ERROR(FAIL, "MPI_File_close failed", mpi_code)

    /* Clean up other stuff */
    H5FD_mpi_comm_info_free(&file->comm, &file->info);
    H5MM_xfree(file);

done:
#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
      fprintf(stdout, "Leaving H5FD_mpio_close\n");
#endif
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_query
 *
 * Purpose:  Set the flags that this VFL driver is capable of supporting.
 *              (listed in H5FDpublic.h)
 *
 * Return:  Success:  non-negative
 *
 *    Failure:  negative
 *
 * Programmer:  Quincey Koziol
 *              Friday, August 25, 2000
 *
 * Modifications:
 *
 *    John Mainzer -- 9/21/05
 *    Modified code to turn off the
 *    H5FD_FEAT_ACCUMULATE_METADATA_WRITE flag.
 *              With the movement of
 *    all cache writes to process 0, this flag has become
 *    problematic in PHDF5.
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_query(const H5FD_t UNUSED *_file, unsigned long *flags /* out */)
{
    FUNC_ENTER_NOAPI_NOINIT_NOERR

    /* Set the VFL feature flags that this driver supports */
    if(flags) {
        *flags=0;
        *flags|=H5FD_FEAT_AGGREGATE_METADATA; /* OK to aggregate metadata allocations */
        *flags|=H5FD_FEAT_AGGREGATE_SMALLDATA; /* OK to aggregate "small" raw data allocations */
    } /* end if */

    FUNC_LEAVE_NOAPI(SUCCEED)
}


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_get_eoa
 *
 * Purpose:  Gets the end-of-address marker for the file. The EOA marker
 *    is the first address past the last byte allocated in the
 *    format address space.
 *
 * Return:  Success:  The end-of-address marker.
 *
 *    Failure:  HADDR_UNDEF
 *
 * Programmer:  Robb Matzke
 *              Friday, August  6, 1999
 *
 * Modifications:
 *              Raymond Lu
 *              21 Dec. 2006
 *              Added the parameter TYPE.  It's only used for MULTI driver.
 *
 *-------------------------------------------------------------------------
 */
static haddr_t
H5FD_mpio_get_eoa(const H5FD_t *_file, H5FD_mem_t UNUSED type)
{
    const H5FD_mpio_t  *file = (const H5FD_mpio_t*)_file;

    FUNC_ENTER_NOAPI_NOINIT_NOERR

    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);

    FUNC_LEAVE_NOAPI(file->eoa)
}


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_set_eoa
 *
 * Purpose:  Set the end-of-address marker for the file. This function is
 *    called shortly after an existing HDF5 file is opened in order
 *    to tell the driver where the end of the HDF5 data is located.
 *
 * Return:  Success:  0
 *
 *    Failure:  -1
 *
 * Programmer:  Robb Matzke
 *              Friday, August 6, 1999
 *
 * Modifications:
 *              Raymond Lu
 *              21 Dec. 2006
 *              Added the parameter TYPE.  It's only used for MULTI driver.
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_set_eoa(H5FD_t *_file, H5FD_mem_t UNUSED type, haddr_t addr)
{
    H5FD_mpio_t  *file = (H5FD_mpio_t*)_file;

    FUNC_ENTER_NOAPI_NOINIT_NOERR

    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);

    file->eoa = addr;

    FUNC_LEAVE_NOAPI(SUCCEED)
}


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_get_eof
 *
 * Purpose:  Gets the end-of-file marker for the file. The EOF marker
 *    is the real size of the file.
 *
 *    The MPIO driver doesn't bother keeping this field updated
 *    since that's a relatively expensive operation. Fortunately
 *    the library only needs the EOF just after the file is opened
 *    in order to determine whether the file is empty, truncated,
 *    or okay.  Therefore, any MPIO I/O function will set its value
 *    to HADDR_UNDEF which is the error return value of this
 *    function.
 *
 *              Keeping the EOF updated (during write calls) is expensive
 *              because any process may extend the physical end of the
 *              file. -QAK
 *
 * Return:  Success:  The end-of-address marker.
 *
 *    Failure:  HADDR_UNDEF
 *
 * Programmer:  Robb Matzke
 *              Friday, August  6, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static haddr_t
H5FD_mpio_get_eof(const H5FD_t *_file)
{
    const H5FD_mpio_t  *file = (const H5FD_mpio_t*)_file;

    FUNC_ENTER_NOAPI_NOINIT_NOERR

    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);

    FUNC_LEAVE_NOAPI(file->eof)
}


/*-------------------------------------------------------------------------
 * Function:       H5FD_mpio_get_handle
 *
 * Purpose:        Returns the file handle of MPIO file driver.
 *
 * Returns:        Non-negative if succeed or negative if fails.
 *
 * Programmer:     Raymond Lu
 *                 Sept. 16, 2002
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
*/
static herr_t
H5FD_mpio_get_handle(H5FD_t *_file, hid_t UNUSED fapl, void** file_handle)
{
    H5FD_mpio_t         *file = (H5FD_mpio_t *)_file;
    herr_t              ret_value = SUCCEED;

    FUNC_ENTER_NOAPI_NOINIT

    if(!file_handle)
        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file handle not valid")

    *file_handle = &(file->f);

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_read
 *
 * Purpose:  Reads SIZE bytes of data from FILE beginning at address ADDR
 *    into buffer BUF according to data transfer properties in
 *    DXPL_ID using potentially complex file and buffer types to
 *    effect the transfer.
 *
 *    Reading past the end of the MPI file returns zeros instead of
 *    failing.  MPI is able to coalesce requests from different
 *    processes (collective or independent).
 *
 * Return:  Success:  Zero. Result is stored in caller-supplied
 *        buffer BUF.
 *
 *    Failure:  -1, Contents of buffer BUF are undefined.
 *
 * Programmer:  rky, 1998-01-30
 *
 * Modifications:
 *     Robb Matzke, 1998-02-18
 *    Added the ACCESS_PARMS argument.
 *
 *     rky, 1998-04-10
 *    Call independent or collective MPI read, based on
 *    ACCESS_PARMS.
 *
 *     Albert Cheng, 1998-06-01
 *    Added XFER_MODE to control independent or collective MPI
 *    read.
 *
 *     rky, 1998-08-16
 *    Use BTYPE, FTYPE, and DISP from access parms. The guts of
 *    H5FD_mpio_read and H5FD_mpio_write should be replaced by a
 *    single dual-purpose routine.
 *
 *     Robb Matzke, 1999-04-21
 *    Changed XFER_MODE to XFER_PARMS for all H5F_*_read()
 *    callbacks.
 *
 *     Robb Matzke, 1999-07-28
 *    The ADDR argument is passed by value.
 *
 *     Robb Matzke, 1999-08-06
 *    Modified to work with the virtual file layer.
 *
 *    Quincey Koziol,  2002-05-14
 *    Only call MPI_Get_count if we can use MPI_BYTE for the MPI type
 *              for the I/O transfer.  Someday we might include code to decode
 *              the MPI type used for more complicated transfers and call
 *              MPI_Get_count all the time.
 *
 *              Quincey Koziol - 2002/06/17
 *              Removed 'disp' parameter from H5FD_mpio_setup routine and use
 *              the address of the dataset in MPI_File_set_view() calls, as
 *              necessary.
 *
 *              Quincey Koziol - 2002/06/24
 *              Removed "lazy" MPI_File_set_view() calls, since they would fail
 *              if the first I/O was a collective I/O using MPI derived types
 *              and the next I/O was an independent I/O.
 *
 *              Quincey Koziol - 2003/10/22-31
 *              Restructured code massively, straightening out logic and finally
 *              getting the bytes_read stuff working.
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_read(H5FD_t *_file, H5FD_mem_t UNUSED type, hid_t dxpl_id, haddr_t addr, size_t size,
         void *buf/*out*/)
{
    H5FD_mpio_t      *file = (H5FD_mpio_t*)_file;
    MPI_Offset      mpi_off;
    MPI_Status      mpi_stat;       /* Status from I/O operation */
    int        mpi_code;  /* mpi return code */
    MPI_Datatype    buf_type = MPI_BYTE;      /* MPI description of the selection in memory */
    int             size_i;         /* Integer copy of 'size' to read */
    int             bytes_read;     /* Number of bytes read in */
    int             n;
    int                         type_size;      /* MPI datatype used for I/O's size */
    int                         io_size;        /* Actual number of bytes requested */
    H5P_genplist_t              *plist = NULL;  /* Property list pointer */
    hbool_t      use_view_this_time = FALSE;
    herr_t                ret_value = SUCCEED;

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
      fprintf(stdout, "Entering H5FD_mpio_read\n" );
#endif
    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);
    /* Make certain we have the correct type of property list */
    HDassert(H5I_GENPROP_LST==H5I_get_type(dxpl_id));
    HDassert(TRUE==H5P_isa_class(dxpl_id,H5P_DATASET_XFER));
    HDassert(buf);

    /* Portably initialize MPI status variable */
    HDmemset(&mpi_stat,0,sizeof(MPI_Status));

    /* some numeric conversions */
    if (H5FD_mpi_haddr_to_MPIOff(addr, &mpi_off/*out*/)<0)
        HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "can't convert from haddr to MPI off")
    size_i = (int)size;
    if ((hsize_t)size_i != size)
        HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "can't convert from size to size_i")

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'r'])
        fprintf(stdout, "in H5FD_mpio_read  mpi_off=%ld  size_i=%d\n",
    (long)mpi_off, size_i );
#endif

    /* Only look for MPI views for raw data transfers */
    if(type==H5FD_MEM_DRAW) {
        H5FD_mpio_xfer_t            xfer_mode;   /* I/O tranfer mode */

        /* Obtain the data transfer properties */
        if(NULL == (plist = (H5P_genplist_t *)H5I_object(dxpl_id)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file access property list")
        xfer_mode = (H5FD_mpio_xfer_t)H5P_peek_unsigned(plist, H5D_XFER_IO_XFER_MODE_NAME);

        /*
         * Set up for a fancy xfer using complex types, or single byte block. We
         * wouldn't need to rely on the use_view field if MPI semantics allowed
         * us to test that btype=ftype=MPI_BYTE (or even MPI_TYPE_NULL, which
         * could mean "use MPI_BYTE" by convention).
         */
        if(xfer_mode==H5FD_MPIO_COLLECTIVE) {
            MPI_Datatype    file_type;

            /* Remember that views are used */
            use_view_this_time = TRUE;

            /* prepare for a full-blown xfer using btype, ftype, and disp */
            if(H5P_get(plist,H5FD_MPI_XFER_MEM_MPI_TYPE_NAME,&buf_type)<0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get MPI-I/O type property")
            if(H5P_get(plist,H5FD_MPI_XFER_FILE_MPI_TYPE_NAME,&file_type)<0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get MPI-I/O type property")

            /*
             * Set the file view when we are using MPI derived types
             */
            /*OKAY: CAST DISCARDS CONST QUALIFIER*/
            if (MPI_SUCCESS != (mpi_code=MPI_File_set_view(file->f, mpi_off, MPI_BYTE, file_type, H5FD_mpi_native_g,  file->info)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_set_view failed", mpi_code)

            /* When using types, use the address as the displacement for
             * MPI_File_set_view and reset the address for the read to zero
             */
            mpi_off=0;
        } /* end if */
    } /* end if */

    /* Read the data. */
    if(use_view_this_time) {
       H5FD_mpio_collective_opt_t coll_opt_mode;

#ifdef H5FDmpio_DEBUG
  if (H5FD_mpio_Debug[(int)'t'])
      fprintf(stdout, "H5FD_mpio_read: using MPIO collective mode\n");
#endif
        /* Peek the collective_opt property to check whether the application wants to do IO individually. */
        HDassert(plist);
        coll_opt_mode = (H5FD_mpio_collective_opt_t)H5P_peek_unsigned(plist, H5D_XFER_MPIO_COLLECTIVE_OPT_NAME);

        if(coll_opt_mode == H5FD_MPIO_COLLECTIVE_IO) {
#ifdef H5FDmpio_DEBUG
            if(H5FD_mpio_Debug[(int)'t'])
                fprintf(stdout, "H5FD_mpio_read: doing MPI collective IO\n");
#endif
            if(MPI_SUCCESS != (mpi_code = MPI_File_read_at_all(file->f, mpi_off, buf, size_i, buf_type, &mpi_stat)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_read_at_all failed", mpi_code)
        } /* end if */
        else {
#ifdef H5FDmpio_DEBUG
            if(H5FD_mpio_Debug[(int)'t'])
                fprintf(stdout, "H5FD_mpio_read: doing MPI independent IO\n");
#endif

            if(MPI_SUCCESS != (mpi_code = MPI_File_read_at(file->f, mpi_off, buf, size_i, buf_type, &mpi_stat)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_read_at failed", mpi_code)
        } /* end else */

        /*
         * Reset the file view when we used MPI derived types
         */
        /*OKAY: CAST DISCARDS CONST QUALIFIER*/
        if(MPI_SUCCESS != (mpi_code = MPI_File_set_view(file->f, (MPI_Offset)0, MPI_BYTE, MPI_BYTE, H5FD_mpi_native_g, file->info)))
            HMPI_GOTO_ERROR(FAIL, "MPI_File_set_view failed", mpi_code)
    } else {
        if(MPI_SUCCESS != (mpi_code = MPI_File_read_at(file->f, mpi_off, buf, size_i, buf_type, &mpi_stat)))
            HMPI_GOTO_ERROR(FAIL, "MPI_File_read_at failed", mpi_code)
    }

    /* How many bytes were actually read? */
    /* [This works because the "basic elements" we use for all our MPI derived
     *  types are MPI_BYTE.  We should be using the 'buf_type' for the MPI
     *  datatype in this call though... (We aren't because using it causes
     *  the LANL "qsc" machine to dump core - 12/19/03) - QAK]
     */
    if (MPI_SUCCESS != (mpi_code=MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_read)))
        HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements failed", mpi_code)

    /* Get the type's size */
    if (MPI_SUCCESS != (mpi_code=MPI_Type_size(buf_type,&type_size)))
        HMPI_GOTO_ERROR(FAIL, "MPI_Type_size failed", mpi_code)

    /* Compute the actual number of bytes requested */
    io_size=type_size*size_i;

    /* Check for read failure */
    if (bytes_read<0 || bytes_read>io_size)
        HGOTO_ERROR(H5E_IO, H5E_READERROR, FAIL, "file read failed")

    /*
     * This gives us zeroes beyond end of physical MPI file.
     */
    if ((n=(io_size-bytes_read)) > 0)
        HDmemset((char*)buf+bytes_read, 0, (size_t)n);

done:
#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
      fprintf(stdout, "Leaving H5FD_mpio_read\n" );
#endif

    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_write
 *
 * Purpose:  Writes SIZE bytes of data to FILE beginning at address ADDR
 *    from buffer BUF according to data transfer properties in
 *    DXPL_ID using potentially complex file and buffer types to
 *    effect the transfer.
 *
 *    MPI is able to coalesce requests from different processes
 *    (collective and independent).
 *
 * Return:  Success:  Zero. USE_TYPES and OLD_USE_TYPES in the
 *        access params are altered.
 *
 *    Failure:  -1, USE_TYPES and OLD_USE_TYPES in the
 *        access params may be altered.
 *
 * Programmer:  Unknown
 *              January 30, 1998
 *
 * Modifications:
 *    rky, 1998-08-28
 *    If the file->allsame flag is set, we assume that all the
 *    procs in the relevant MPI communicator will write identical
 *    data at identical offsets in the file, so only proc 0 will
 *    write, and all other procs will wait for p0 to finish. This
 *    is useful for writing metadata, for example. Note that we
 *    don't _check_ that the data is identical. Also, the mechanism
 *    we use to eliminate the redundant writes is by requiring a
 *    call to H5FD_mpio_tas_allsame before the write, which is
 *    rather klugey. Would it be better to pass a parameter to
 *    low-level writes like H5F_block_write and H5F_low_write,
 *    instead?  Or...??? Also, when I created this mechanism I
 *    wanted to minimize the difference in behavior between the old
 *    way of doing things (i.e., all procs write) and the new way,
 *    so the writes are eliminated at the very lowest level, here
 *    in H5FD_mpio_write. It may be better to rethink that, and
 *    short-circuit the writes at a higher level (e.g., at the
 *    points in the code where H5FD_mpio_tas_allsame is called).
 *
 *
 *     Robb Matzke, 1998-02-18
 *    Added the ACCESS_PARMS argument.
 *
 *     rky, 1998-04-10
 *    Call independent or collective MPI write, based on
 *    ACCESS_PARMS.
 *
 *     rky, 1998-04-24
 *    Removed redundant write from H5FD_mpio_write.
 *
 *     Albert Cheng, 1998-06-01
 *    Added XFER_MODE to control independent or collective MPI
 *    write.
 *
 *     rky, 1998-08-16
 *    Use BTYPE, FTYPE, and DISP from access parms. The guts of
 *    H5FD_mpio_read and H5FD_mpio_write should be replaced by a
 *    single dual-purpose routine.
 *
 *     rky, 1998-08-28
 *    Added ALLSAME parameter to make all but proc 0 skip the
 *    actual write.
 *
 *     Robb Matzke, 1999-04-21
 *    Changed XFER_MODE to XFER_PARMS for all H5FD_*_write()
 *    callbacks.
 *
 *     Robb Matzke, 1999-07-28
 *    The ADDR argument is passed by value.
 *
 *     Robb Matzke, 1999-08-06
 *    Modified to work with the virtual file layer.
 *
 *    Albert Cheng, 1999-12-19
 *    When only-p0-write-allsame-data, p0 Bcasts the
 *    ret_value to other processes.  This prevents
 *    a racing condition (that other processes try to
 *    read the file before p0 finishes writing) and also
 *    allows all processes to report the same ret_value.
 *
 *    Kim Yates, Pat Weidhaas,  2000-09-26
 *    Move block of coding where only p0 writes after the
 *              MPI_File_set_view call.
 *
 *    Quincey Koziol,  2002-05-10
 *    Instead of always writing metadata from process 0, spread the
 *              burden among all the processes by using a round-robin rotation
 *              scheme.
 *
 *    Quincey Koziol,  2002-05-10
 *    Removed allsame code, keying off the type parameter instead.
 *
 *    Quincey Koziol,  2002-05-14
 *    Only call MPI_Get_count if we can use MPI_BYTE for the MPI type
 *              for the I/O transfer.  Someday we might include code to decode
 *              the MPI type used for more complicated transfers and call
 *              MPI_Get_count all the time.
 *
 *              Quincey Koziol - 2002/06/17
 *              Removed 'disp' parameter from H5FD_mpio_setup routine and use
 *              the address of the dataset in MPI_File_set_view() calls, as
 *              necessary.
 *
 *              Quincey Koziol - 2002/06/24
 *              Removed "lazy" MPI_File_set_view() calls, since they would fail
 *              if the first I/O was a collective I/O using MPI derived types
 *              and the next I/O was an independent I/O.
 *
 *              Quincey Koziol - 2002/07/18
 *              Added "block_before_meta_write" dataset transfer flag, which
 *              is set during writes from a metadata cache flush and indicates
 *              that all the processes must sync up before (one of them)
 *              writing metadata.
 *
 *              Quincey Koziol - 2003/10/22-31
 *              Restructured code massively, straightening out logic and finally
 *              getting the bytes_written stuff working.
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_write(H5FD_t *_file, H5FD_mem_t type, hid_t dxpl_id, haddr_t addr,
    size_t size, const void *buf)
{
    H5FD_mpio_t      *file = (H5FD_mpio_t*)_file;
    MPI_Offset        mpi_off;
    MPI_Status      mpi_stat;       /* Status from I/O operation */
    MPI_Datatype    buf_type = MPI_BYTE;      /* MPI description of the selection in memory */
    int              mpi_code;  /* MPI return code */
    int             size_i, bytes_written;
    int                         type_size;      /* MPI datatype used for I/O's size */
    int                         io_size;        /* Actual number of bytes requested */
    hbool_t      use_view_this_time = FALSE;
    H5P_genplist_t              *plist = NULL;  /* Property list pointer */
    herr_t                ret_value = SUCCEED;

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if (H5FD_mpio_Debug[(int)'t'])
      fprintf(stdout, "Entering H5FD_mpio_write\n" );
#endif
    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);
    /* Make certain we have the correct type of property list */
    HDassert(H5I_GENPROP_LST==H5I_get_type(dxpl_id));
    HDassert(TRUE==H5P_isa_class(dxpl_id,H5P_DATASET_XFER));
    HDassert(buf);

    /* Portably initialize MPI status variable */
    HDmemset(&mpi_stat, 0, sizeof(MPI_Status));

    /* some numeric conversions */
    if(H5FD_mpi_haddr_to_MPIOff(addr, &mpi_off) < 0)
        HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "can't convert from haddr to MPI off")
    size_i = (int)size;
    if((hsize_t)size_i != size)
        HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "can't convert from size to size_i")

#ifdef H5FDmpio_DEBUG
    if(H5FD_mpio_Debug[(int)'w'])
        fprintf(stdout, "in H5FD_mpio_write  mpi_off=%ld  size_i=%d\n", (long)mpi_off, size_i);
#endif

    if(type == H5FD_MEM_DRAW) {
        H5FD_mpio_xfer_t            xfer_mode;   /* I/O tranfer mode */

        /* Obtain the data transfer properties */
        if(NULL == (plist = (H5P_genplist_t *)H5I_object(dxpl_id)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a file access property list")

        /* Obtain the data transfer properties */
        xfer_mode = (H5FD_mpio_xfer_t)H5P_peek_unsigned(plist, H5D_XFER_IO_XFER_MODE_NAME);

        /*
         * Set up for a fancy xfer using complex types, or single byte block. We
         * wouldn't need to rely on the use_view field if MPI semantics allowed
         * us to test that btype=ftype=MPI_BYTE (or even MPI_TYPE_NULL, which
         * could mean "use MPI_BYTE" by convention).
         */
        if(xfer_mode == H5FD_MPIO_COLLECTIVE) {
            MPI_Datatype    file_type;

            /* Remember that views are used */
            use_view_this_time = TRUE;

            /* prepare for a full-blown xfer using btype, ftype, and disp */
            if(H5P_get(plist, H5FD_MPI_XFER_MEM_MPI_TYPE_NAME, &buf_type) < 0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get MPI-I/O type property")
            if(H5P_get(plist, H5FD_MPI_XFER_FILE_MPI_TYPE_NAME, &file_type) < 0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get MPI-I/O type property")

            /*
             * Set the file view when we are using MPI derived types
             */
            /*OKAY: CAST DISCARDS CONST QUALIFIER*/
            if(MPI_SUCCESS != (mpi_code = MPI_File_set_view(file->f, mpi_off, MPI_BYTE, file_type, H5FD_mpi_native_g, file->info)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_set_view failed", mpi_code)

            /* When using types, use the address as the displacement for
             * MPI_File_set_view and reset the address for the read to zero
             */
            mpi_off = 0;
        } /* end if */
    } /* end if */
    else {
#if 0 /* JRM -- 3/23/10 */ /* this is no longer always the case */
        /* Only one process can do the actual metadata write */
        if(file->mpi_rank != H5_PAR_META_WRITE)
#ifdef LATER
            HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "can't write metadata from non-zero rank")
#else /* LATER */
            HGOTO_DONE(SUCCEED) /* skip the actual write */
#endif /* LATER */
#endif /* JRM */
    } /* end if */

    /* Write the data. */
    if(use_view_this_time) {
        H5FD_mpio_collective_opt_t coll_opt_mode;

#ifdef H5FDmpio_DEBUG
        if(H5FD_mpio_Debug[(int)'t'])
            fprintf(stdout, "H5FD_mpio_write: using MPIO collective mode\n");
#endif
        /* Peek the collective_opt property to check whether the application wants to do IO individually. */
        HDassert(plist);
        coll_opt_mode = (H5FD_mpio_collective_opt_t)H5P_peek_unsigned(plist, H5D_XFER_MPIO_COLLECTIVE_OPT_NAME);

        /*OKAY: CAST DISCARDS CONST QUALIFIER*/
        if(coll_opt_mode == H5FD_MPIO_COLLECTIVE_IO) {
#ifdef H5FDmpio_DEBUG
            if(H5FD_mpio_Debug[(int)'t'])
                fprintf(stdout, "H5FD_mpio_write: doing MPI collective IO\n");
#endif
            if(MPI_SUCCESS != (mpi_code = MPI_File_write_at_all(file->f, mpi_off, (void*)buf, size_i, buf_type, &mpi_stat)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_write_at_all failed", mpi_code)
        } /* end if */
        else {
#ifdef H5FDmpio_DEBUG
            if(H5FD_mpio_Debug[(int)'t'])
                fprintf(stdout, "H5FD_mpio_write: doing MPI independent IO\n");
#endif
            if(MPI_SUCCESS != (mpi_code = MPI_File_write_at(file->f, mpi_off, (void*)buf, size_i, buf_type, &mpi_stat)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_write_at failed", mpi_code)
        } /* end else */

        /* Reset the file view when we used MPI derived types */
        /*OKAY: CAST DISCARDS CONST QUALIFIER*/
        if(MPI_SUCCESS != (mpi_code = MPI_File_set_view(file->f, (MPI_Offset)0, MPI_BYTE, MPI_BYTE, H5FD_mpi_native_g,  file->info)))
            HMPI_GOTO_ERROR(FAIL, "MPI_File_set_view failed", mpi_code)
    } else {
        /*OKAY: CAST DISCARDS CONST QUALIFIER*/
        if(MPI_SUCCESS != (mpi_code = MPI_File_write_at(file->f, mpi_off, (void*)buf, size_i, buf_type, &mpi_stat)))
            HMPI_GOTO_ERROR(FAIL, "MPI_File_write_at failed", mpi_code)
    }

    /* How many bytes were actually written? */
    /* [This works because the "basic elements" we use for all our MPI derived
     *  types are MPI_BYTE.  We should be using the 'buf_type' for the MPI
     *  datatype in this call though... (We aren't because using it causes
     *  the LANL "qsc" machine to dump core - 12/19/03) - QAK]
     */
    if(MPI_SUCCESS != (mpi_code = MPI_Get_elements(&mpi_stat, MPI_BYTE, &bytes_written)))
        HMPI_GOTO_ERROR(FAIL, "MPI_Get_elements failed", mpi_code)

    /* Get the type's size */
    if(MPI_SUCCESS != (mpi_code = MPI_Type_size(buf_type, &type_size)))
        HMPI_GOTO_ERROR(FAIL, "MPI_Type_size failed", mpi_code)

    /* Compute the actual number of bytes requested */
    io_size = type_size * size_i;

    /* Check for write failure */
    if(bytes_written != io_size)
        HGOTO_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "file write failed")

    /* Forget the EOF value (see H5FD_mpio_get_eof()) --rpm 1999-08-06 */
    file->eof = HADDR_UNDEF;

done:
#ifdef H5FDmpio_DEBUG
    if(H5FD_mpio_Debug[(int)'t'])
      fprintf(stdout, "proc %d: Leaving H5FD_mpio_write with ret_value=%d\n",
      file->mpi_rank, ret_value );
#endif
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD_mpio_write() */


/*-------------------------------------------------------------------------
 * Function:    H5FD_mpio_flush
 *
 * Purpose:     Makes sure that all data is on disk.  This is collective.
 *
 * Return:      Success:  Non-negative
 *
 *     Failure:  Negative
 *
 * Programmer:  Robb Matzke
 *              January 30, 1998
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_flush(H5FD_t *_file, hid_t UNUSED dxpl_id, unsigned closing)
{
    H5FD_mpio_t    *file = (H5FD_mpio_t*)_file;
    int      mpi_code;  /* mpi return code */
    herr_t              ret_value = SUCCEED;

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if(H5FD_mpio_Debug[(int)'t'])
      HDfprintf(stdout, "Entering %s\n", FUNC);
#endif
    HDassert(file);
    HDassert(H5FD_MPIO == file->pub.driver_id);

    /* Only sync the file if we are not going to immediately close it */
    if(!closing) {
        if(MPI_SUCCESS != (mpi_code = MPI_File_sync(file->f)))
            HMPI_GOTO_ERROR(FAIL, "MPI_File_sync failed", mpi_code)
    } /* end if */

done:
#ifdef H5FDmpio_DEBUG
    if(H5FD_mpio_Debug[(int)'t'])
      HDfprintf(stdout, "Leaving %s\n", FUNC);
#endif

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD_mpio_flush() */


/*-------------------------------------------------------------------------
 * Function:    H5FD_mpio_truncate
 *
 * Purpose:     Make certain the file's size matches it's allocated size
 *
 * Return:      Success:  Non-negative
 *     Failure:  Negative
 *
 * Programmer:  Quincey Koziol
 *              January 31, 2008
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5FD_mpio_truncate(H5FD_t *_file, hid_t UNUSED dxpl_id, hbool_t UNUSED closing)
{
    H5FD_mpio_t    *file = (H5FD_mpio_t*)_file;
    herr_t              ret_value = SUCCEED;

    FUNC_ENTER_NOAPI_NOINIT

#ifdef H5FDmpio_DEBUG
    if(H5FD_mpio_Debug[(int)'t'])
      HDfprintf(stdout, "Entering %s\n", FUNC);
#endif
    HDassert(file);
    HDassert(H5FD_MPIO == file->pub.driver_id);

    /* Extend the file to make sure it's large enough, then sync.
     * Unfortunately, keeping track of EOF is an expensive operation, so
     * we can't just check whether EOF<EOA like with other drivers.
     * Therefore we'll just read the byte at EOA-1 and then write it back. */
    if(file->eoa > file->last_eoa) {
        int    mpi_code;  /* mpi return code */
        MPI_Offset      mpi_off;

#ifdef H5_MPI_FILE_SET_SIZE_BIG
        if(H5FD_mpi_haddr_to_MPIOff(file->eoa, &mpi_off) < 0)
            HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "cannot convert from haddr_t to MPI_Offset")

        /* Extend the file's size */
        if(MPI_SUCCESS != (mpi_code = MPI_File_set_size(file->f, mpi_off)))
            HMPI_GOTO_ERROR(FAIL, "MPI_File_set_size failed", mpi_code)
#else /* H5_MPI_FILE_SET_SIZE_BIG */
  /* Wait until all processes are here before reading/writing the byte at
         * process 0's end of address space.  The window for corruption is
         * probably tiny, but does exist...
         */
        if(MPI_SUCCESS != (mpi_code = MPI_Barrier(file->comm)))
            HMPI_GOTO_ERROR(FAIL, "MPI_Barrier failed", mpi_code)

        if(0 == file->mpi_rank) {
            uint8_t             byte = 0;
            MPI_Status          mpi_stat;

            /* Portably initialize MPI status variable */
            HDmemset(&mpi_stat, 0, sizeof(MPI_Status));

            if(H5FD_mpi_haddr_to_MPIOff(file->eoa-1, &mpi_off) < 0)
                HGOTO_ERROR(H5E_INTERNAL, H5E_BADRANGE, FAIL, "cannot convert from haddr_t to MPI_Offset")
            if(MPI_SUCCESS != (mpi_code = MPI_File_read_at(file->f, mpi_off, &byte, 1, MPI_BYTE, &mpi_stat)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_read_at failed", mpi_code)
            if(MPI_SUCCESS != (mpi_code = MPI_File_write_at(file->f, mpi_off, &byte, 1, MPI_BYTE, &mpi_stat)))
                HMPI_GOTO_ERROR(FAIL, "MPI_File_write_at failed", mpi_code)
        } /* end if */
#endif /* H5_MPI_FILE_SET_SIZE_BIG */

  /* Don't let any proc return until all have extended the file.
         * (Prevents race condition where some processes go ahead and write
         * more data to the file before all the processes have finished making
         * it the shorter length, potentially truncating the file and dropping
         * the new data written)
         */
        if(MPI_SUCCESS != (mpi_code = MPI_Barrier(file->comm)))
            HMPI_GOTO_ERROR(FAIL, "MPI_Barrier failed", mpi_code)

        /* Update the 'last' eoa value */
        file->last_eoa = file->eoa;
    } /* end if */

done:
#ifdef H5FDmpio_DEBUG
    if(H5FD_mpio_Debug[(int)'t'])
      HDfprintf(stdout, "Leaving %s\n", FUNC);
#endif

    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5FD_mpio_truncate() */


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_mpi_rank
 *
 * Purpose:  Returns the MPI rank for a process
 *
 * Return:  Success: non-negative
 *    Failure: negative
 *
 * Programmer:  Quincey Koziol
 *              Thursday, May 16, 2002
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static int
H5FD_mpio_mpi_rank(const H5FD_t *_file)
{
    const H5FD_mpio_t  *file = (const H5FD_mpio_t*)_file;

    FUNC_ENTER_NOAPI_NOINIT_NOERR

    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);

    FUNC_LEAVE_NOAPI(file->mpi_rank)
} /* end H5FD_mpio_mpi_rank() */


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_mpi_size
 *
 * Purpose:  Returns the number of MPI processes
 *
 * Return:  Success: non-negative
 *    Failure: negative
 *
 * Programmer:  Quincey Koziol
 *              Thursday, May 16, 2002
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static int
H5FD_mpio_mpi_size(const H5FD_t *_file)
{
    const H5FD_mpio_t  *file = (const H5FD_mpio_t*)_file;

    FUNC_ENTER_NOAPI_NOINIT_NOERR

    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);

    FUNC_LEAVE_NOAPI(file->mpi_size)
} /* end H5FD_mpio_mpi_size() */


/*-------------------------------------------------------------------------
 * Function:  H5FD_mpio_communicator
 *
 * Purpose:  Returns the MPI communicator for the file.
 *
 * Return:  Success:  The communicator
 *
 *    Failure:  NULL
 *
 * Programmer:  Robb Matzke
 *              Monday, August  9, 1999
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static MPI_Comm
H5FD_mpio_communicator(const H5FD_t *_file)
{
    const H5FD_mpio_t  *file = (const H5FD_mpio_t*)_file;

    FUNC_ENTER_NOAPI_NOINIT_NOERR

    HDassert(file);
    HDassert(H5FD_MPIO==file->pub.driver_id);

    FUNC_LEAVE_NOAPI(file->comm)
}

#endif /* H5_HAVE_PARALLEL */