Table of Contents

Modifying the Program Running this Legion-PVM Program Limitations of this "fewest changes" approach Modifying the program for the Typed Binary Interface Other on-line tutorials & documentation

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Modifying the Program

Consider the following PVM program stub, which runs a binary named example:

           program foo

           implicit none
           include 'fpvm3.h'
           integer info, mytid, myparent, numprocs, numret
           integer tids(0:MAXNCHILD)
           logical master
           integer i, j, k

c      Get numprocs somewhere

           call pvmfmytid( mytid )
           call pvmfmyparent( tids(0) )
           
           if ( tids(0) .eq. PVMNOPARENT ) then
               master = .true.
               call pvmfspawn( 'example', PVMDEFAULT, '*', 
    &                           numprocs, tids, numret)
           endif

           if ( master ) then
              open (10, file = 'input', status = 'old')
              read (10,*) i, j, k
              close (10)
           endif

           call do_work (i, j, k)

           if ( master ) then
              open (11, file = 'output', status = 'new' )
              write (11, *) i, j, k
              close (11)
           endif

           call pvmfexit(info)
           stop
           end

In order to run this program over Legion and get the benefit of remote I/O, it is necessary to insert extra I/O calls. The PVM calls do not change. Here is the result, in which the changes are in upper case:

           program foo

           implicit none
           include 'fpvm3.h'
           integer info, mytid, myparent, numprocs, numret
           integer tids(0:MAXNCHILD)
           logical master
           integer i, j, k
           CHARACTER*256 INPUT, OUTPUT

c      Get numprocs somewhere

           call pvmfmytid( mytid )
           call pvmfmyparent( tids(0) )
           
           if ( tids(0) .eq. PVMNOPARENT ) then
               master = .true.
               call pvmfspawn( 'example', PVMDEFAULT, '*', 
    &                           numprocs, tids, numret)
           endif

           if ( master ) then
              CALL LIOF_LEGION_TO_TEMPFILE ('input', INPUT, info)
              open (10, file = INPUT, status = 'old')
              read (10,*) i, j, k
              close (10)
           endif

           call do_work (i, j, k)

           if ( master ) then
              CALL LIOF_CREATE_TEMPFILE (OUTPUT, IERR)
              open (11, file = OUTPUT, status = 'new' )
              write (11, *) i, j, k
              close (11)
              CALL LIOF_TEMPFILE_TO_LEGION (OUTPUT, 'output', IERR)
           endif

           call pvmfexit(info)
           stop
           end

              CHARACTER*256 INPUT, OUTPUT

              call LIOF_LEGION_TO_TEMPFILE ('input', INPUT, info)

              open (10, file = INPUT, status = 'old')

              call LIOF_CREATE_TEMPFILE (OUTPUT, IERR)

              open (11, file = OUTPUT, status = 'new' )

              call LIOF_TEMPFILE_TO_LEGION (OUTPUT, 'output', IERR)

Running this Legion-PVM Program

In order to run this program under Legion PVM, we need to:

• compile and link the program
• set up access to the Legion system
• tell Legion where the executable and input file are
• run the program
• copy the output file back to our workstation

1. Compiling and linking

   Assuming that our program is in the file example.f, we would compile and link using:

    % f77 -c example.f -I$LEGION/include/pvm3.3 \
     legion_link -Fortran -pvm -o example example.o

2. Setting up access to the Legion system

   Before you issue Legion commands, you may need to execute an extra command:

   % . /home/appnet/setup.sh

   or

   % source /home/appnet/setup.csh

   Also, before you run a Legion program, it is useful to have a Legion tty, which is an object which allows you to observe the output of your program.

   % legion_tty my_tty

   This creates a tty with the name my-tty in Legion space, and send the output from this tty object to your current terminal.

3. Tell Legion where the executable and input file are:

   • executable

        % legion_mpi_register ./example example $LEGION_ARCH

     This command registers the Unix file ./example as the PVM Class example. Legion will create a class object, named /pvm/tasks/example, in Legion space.

   • input file

        % legion_cp -localsource ./input input

     This command creates a Legion FileObject with the name input, and copies the Unix file with the name ./input into it.

4. Run the program

   Now you may run the program:

   % legion_run_pvm /pvm/tasks/example

   This command will run your program somewhere in the Legion system. Any output sent to the screen will be sent to your tty object.

5. Copy the output file back to our workstation

   Finally, we might want to copy the output file named output in Legion space back to our local workstation.

   legion_cp -localdest output ./output

Limitations of this "fewest changes" approach

While this approach allows you to run PVM programs and transparently read and write files remotely, it does have one limitation: it does not support heterogeneous conversions of data. If you run this program on several machines which have different formats for an integer, such as Intel PCs (little-endian) and IBM RS/6000s (big-endian), the result of using unformatted I/O will be surprising. If you want to use such a heterogeneous system, you will have to either use formatted I/O (all files are text) or use the "typed binary" I/O calls instead of Fortran READ and WRITE statements. These "typed binary" I/O calls are discussed in "Buffered I/O Library, low impact interface," in the Legion Developer Manual.

Modifying the program for the Typed Binary Interface

Here's how the program would change if we used the typed binary interface:

           program foo

           implicit none
           include 'fpvm3.h'
           integer info, mytid, myparent, numprocs, numret
           integer tids(0:MAXNCHILD)
           logical master
           integer i, j, k
           integer fd, ierr

c      Get numprocs somewhere

           call pvmfmytid( mytid )
           call pvmfmyparent( tids(0) )
           
           if ( tids(0) .eq. PVMNOPARENT ) then
               master = .true.
               call pvmfspawn( 'example', PVMDEFAULT, '*', 
    &                           numprocs, tids, numret)
           endif

           if ( master ) then
              CALL LIOF_OPEN ('input', 0, FD)
              CALL LIOF_READ_INTS (FD, I, 1, IERR)
              CALL LIOF_READ_INTS (FD, J, 1, IERR)
              CALL LIOF_READ_INTS (FD, K, 1, IERR)
              CALL LIOF_CLOSE (FD, IERR)
           endif

           call do_work (i, j, k)

           if ( master ) then
              call LIOF_OPEN ('output', 0, FD)
              call LIOF_WRITE_INTS (FD, I, 1, IERR)
              call LIOF_WRITE_INTS (FD, J, 1, IERR)
              call LIOF_WRITE_INTS (FD, K, 1, IERR)
              call LIOF_CLOSE (FD, IERR)
           endif

           call pvmfexit(info)
           stop
           end

Running the program is the same as in the previous example.

---

Other relevant on-line documents:

	Click on the to go to the page.
	Logging in to a running Legion system Legion graphical user interface Introduction to Legion context space Context-related commands How to start remote programs in Legion Sample makefile for remote programs Adapting a parameter space study for Legion Object permissions Legion tty objects		Running a PVM code in Legion Running a Legion MPI code Running native MPI code Quick list of all Legion commands (1.6.4) Usage of all Legion commands (1.6.4) Starting a new Legion system Using Legion security features Legion host and vault objects Adding host and vault objects Brief descriptions of all on-line 1.6 tutorials

Last modified: Fri Jun 4 15:16:38 1999

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