readme

mpi并行计算的c++代码 可用vc或gcc编译通过 可以用来搭建并行计算试验环境

status variable is filled only when used with MPICH 1.2.1 or later.

You can open files on multiple file systems in the same program. The
only restriction is that the directory where the file is to be opened
must be accessible from the process opening the file. For example, a
process running on one workstation may not be able to access a
directory on the local disk of another workstation, and therefore
ROMIO will not be able to open a file in such a directory. NFS-mounted
files can be accessed.

An MPI-IO file created by ROMIO is no different than any other file
created by the underlying file system. Therefore, you may use any of
the commands provided by the file system to access the file, e.g., ls,
mv, cp, rm, ftp.


Using ROMIO on NFS
------------------

To use ROMIO on NFS, file locking with fcntl must work correctly on
the NFS installation. On some installations, fcntl locks don't work.
To get them to work, you need to use Version 3 of NFS, ensure that the
lockd daemon is running on all the machines, and have the system
administrator mount the NFS file system with the "noac" option (no
attribute caching). Turning off attribute caching may reduce
performance, but it is necessary for correct behavior.

The following are some instructions we received from Ian Wells of HP
for setting the noac option on NFS. We have not tried them
ourselves. We are including them here because you may find 
them useful. Note that some of the steps may be specific to HP
systems, and you may need root permission to execute some of the
commands. 
   
   >1. first confirm you are running nfs version 3
   >
   >rpcnfo -p `hostname` | grep nfs
   >
   >ie 
   >    goedel >rpcinfo -p goedel | grep nfs
   >    100003    2   udp   2049  nfs
   >    100003    3   udp   2049  nfs
   >
   >
   >2. then edit /etc/fstab for each nfs directory read/written by MPIO
   >   on each  machine used for multihost MPIO.
   >
   >    Here is an example of a correct fstab entry for /epm1:
   >
   >   ie grep epm1 /etc/fstab
   > 
   >      ROOOOT 11>grep epm1 /etc/fstab
   >      gershwin:/epm1 /rmt/gershwin/epm1 nfs bg,intr,noac 0 0
   >
   >   if the noac option is not present, add it 
   >   and then remount this directory
   >   on each of the machines that will be used to share MPIO files
   >
   >ie
   >
   >ROOOOT >umount /rmt/gershwin/epm1
   >ROOOOT >mount  /rmt/gershwin/epm1
   >
   >3. Confirm that the directory is mounted noac:
   >
   >ROOOOT >grep gershwin /etc/mnttab 
   >gershwin:/epm1 /rmt/gershwin/epm1 nfs
   >noac,acregmin=0,acregmax=0,acdirmin=0,acdirmax=0 0 0 899911504




ROMIO Installation Instructions
-------------------------------

Since ROMIO is included in MPICH, LAM, HP MPI, SGI MPI, and NEC MPI,
you don't need to install it separately if you are using any of these
MPI implementations.  If you are using some other MPI, you can
configure and build ROMIO as follows:

Untar the tar file as

    gunzip -c romio.tar.gz | tar xvf -

OR

    zcat romio.tar.Z | tar xvf -

THEN

    cd romio
    ./configure
    make

Some example programs and a Makefile are provided in the romio/test directory.
Run the examples the way you would run any MPI program. Each program takes 
the filename as a command-line argument "-fname filename".  

The configure script by default configures ROMIO for the file systems
most likely to be used on the given machine. If you wish, you can
explicitly specify the file systems by using the "-file_system" option
to configure. Multiple file systems can be specified by using "+" as a
separator. For example,

    ./configure -file_system=xfs+nfs

For the entire list of options to configure do

    ./configure -h | more

After building a specific version as above, you can install it in a
particular directory with 

    make install PREFIX=/usr/local/romio    (or whatever directory you like)

or just

    make install           (if you used -prefix at configure time)

If you intend to leave ROMIO where you built it, you should NOT install it 
(install is used only to move the necessary parts of a built ROMIO to 
another location). The installed copy will have the include files,
libraries, man pages, and a few other odds and ends, but not the whole
source tree.  It will have a test directory for testing the
installation and a location-independent Makefile built during
installation, which users can copy and modify to compile and link
against the installed copy. 

To rebuild ROMIO with a different set of configure options, do

    make distclean

to clean everything including the Makefiles created by configure.
Then run configure again with the new options, followed by make.



Testing ROMIO
-------------

To test if the installation works, do

     make testing 

in the romio/test directory. This calls a script that runs the test
programs and compares the results with what they should be. By
default, "make testing" causes the test programs to create files in
the current directory and use whatever file system that corresponds
to. To test with other file systems, you need to specify a filename in
a directory corresponding to that file system as follows:

     make testing TESTARGS="-fname=/foo/piofs/test"



Compiling and Running MPI-IO Programs
-------------------------------------

If ROMIO is not already included in the MPI implementation, you need
to include the file mpio.h for C or mpiof.h for Fortran in your MPI-IO
program.  

Note that on HP machines running HPUX and on NEC SX-4, you need to
compile Fortran programs with mpif90, because the f77 compilers on
these machines don't support 8-byte integers. 

With MPICH, HP MPI, or NEC MPI, you can compile MPI-IO programs as 
   mpicc foo.c
or 
   mpif77 foo.f
or
   mpif90 foo.f

As mentioned above, mpif90 is preferred over mpif77 on HPUX and NEC
because the f77 compilers on those machines do not support 8-byte integers.

With SGI MPI, you can compile MPI-IO programs as 
   cc foo.c -lmpi
or
   f77 foo.f -lmpi
or
   f90 foo.f -lmpi

With LAM, you can compile MPI-IO programs as 
   hcc foo.c -lmpi
or
   hf77 foo.f -lmpi

If you have built ROMIO with some other MPI implementation, you can
compile MPI-IO programs by explicitly giving the path to the include
file mpio.h or mpiof.h and explicitly specifying the path to the
library libmpio.a, which is located in $(ROMIO_HOME)/lib/$(ARCH)/libmpio.a .


Run the program as you would run any MPI program on the machine. If
you use mpirun, make sure you use the correct mpirun for the MPI
implementation you are using. For example, if you are using MPICH on
an SGI machine, make sure that you use MPICH's mpirun and not SGI's
mpirun.

The Makefile in the romio/test directory illustrates how to compile
and link MPI-IO programs. 



Limitations of this version of ROMIO
------------------------------------

* When used with any MPI implementation other than MPICH 1.2.1 (or later),
the "status" argument is not filled in any MPI-IO function. Consequently,
MPI_Get_count and MPI_Get_elements will not work when passed the status
object from an MPI-IO operation.

* All nonblocking I/O functions use a ROMIO-defined "MPIO_Request"
object instead of the usual "MPI_Request" object. Accordingly, two
functions, MPIO_Test and MPIO_Wait, are provided to wait and test on
these MPIO_Request objects. They have the same semantics as MPI_Test
and MPI_Wait.

int MPIO_Test(MPIO_Request *request, int *flag, MPI_Status *status);
int MPIO_Wait(MPIO_Request *request, MPI_Status *status);

The usual functions MPI_Test, MPI_Wait, MPI_Testany, etc., will not
work for nonblocking I/O. 

* This version works only on a homogeneous cluster of machines,
and only the "native" file data representation is supported.

* When used with any MPI implementation other than MPICH 1.2.1 (or later),
all MPI-IO functions return only two possible error codes---MPI_SUCCESS
on success and MPI_ERR_UNKNOWN on failure.

* Shared file pointers are not supported on PVFS and IBM PIOFS file
systems because they don't support fcntl file locks, and ROMIO uses
that feature to implement shared file pointers.

* On HP machines running HPUX and on NEC SX-4, you need to compile
Fortran programs with mpif90 instead of mpif77, because the f77
compilers on these machines don't support 8-byte integers.

* The file-open mode MPI_MODE_EXCL does not work on Intel PFS file system,
due to a bug in PFS.



Usage Tips
----------

* When using ROMIO with SGI MPI, you may sometimes get an error
message from SGI MPI: ``MPI has run out of internal datatype
entries. Please set the environment variable MPI_TYPE_MAX for
additional space.'' If you get this error message, add this line to
your .cshrc file:
    setenv MPI_TYPE_MAX 65536 
Use a larger number if you still get the error message.

* If a Fortran program uses a file handle created using ROMIO's C
interface, or vice-versa, you must use the functions MPI_File_c2f 
or MPI_File_f2c (see MPI-2 Section 4.12.4). Such a situation occurs,
for example, if a Fortran program uses an I/O library written in C
with MPI-IO calls. Similar functions MPIO_Request_f2c and
MPIO_Request_c2f are also provided.

* For Fortran programs on the Intel Paragon, you may need
to provide the complete path to mpif.h in the include statement, e.g.,
        include '/usr/local/mpich/include/mpif.h'
instead of 
        include 'mpif.h'
This is because the -I option to the Paragon Fortran compiler if77
doesn't work correctly. It always looks in the default directories first 
and, therefore, picks up Intel's mpif.h, which is actually the
mpif.h of an older version of MPICH. 



ROMIO Users Mailing List
------------------------

Please register your copy of ROMIO with us by sending email
to [e-mail] with the message

subscribe romio-users

This will enable us to notify you of new releases of ROMIO as well as
bug fixes.



Reporting Bugs
--------------

If you have trouble, first check the users guide (in
romio/doc/users-guide.ps.gz). Then check the on-line list of known
bugs and patches at http://www.mcs.anl.gov/romio .
Finally, if you still have problems, send a detailed message containing:

   The type of system (often, uname -a)
   The output of configure
   The output of make
   Any programs or tests

to [e-mail] .



ROMIO Internals
---------------

A key component of ROMIO that enables such a portable MPI-IO
implementation is an internal abstract I/O device layer called
ADIO. Most users of ROMIO will not need to deal with the ADIO layer at
all. However, ADIO is useful to those who want to port ROMIO to some
other file system. The ROMIO source code and the ADIO paper
(see doc/README) will help you get started.

MPI-IO implementation issues are discussed in our IOPADS '99 paper,
"On Implementing MPI-IO Portably and with High Performance."
All ROMIO-related papers are available online from
http://www.mcs.anl.gov/romio.


Learning MPI-IO
---------------

The book "Using MPI-2: Advanced Features of the Message-Passing
Interface," published by MIT Press, provides a tutorial introduction to
all aspects of MPI-2, including parallel I/O. It has lots of example
programs. See http://www.mcs.anl.gov/mpi/usingmpi2 for further
information about the book.