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<html>
<head>
<title>
MPI - FORTRAN90 Examples
</title>
</head>
<body bgcolor="#EEEEEE" link="#CC0000" alink="#FF3300" vlink="#000055">
<h1 align = "center">
MPI <br> FORTRAN90 Examples
</h1>
<hr>
<p>
<b>MPI</b>
is a directory of FORTRAN90 programs which
illustrate the use of the MPI
Message Passing Interface.
</p>
<p>
<b>MPI</b> is a library of message passing routines. The library
allows a user to write a program in a familiar language, such as
C, C++, FORTRAN77 or FORTRAN90, and carry out a computation in
parallel on an arbitrary number of cooperating computers.
</p>
<h3 align = "center">
Overview of MPI
</h3>
<p>
A remarkable feature of <b>MPI</b> is that <i>the user writes
a single program which runs on all the computers</i>. However,
because each computer is assigned a unique identifying number,
it is possible for different actions to occur on different
machines, even though they run the same program:
<pre><code>
if ( I am processor A ) then
add a bunch of numbers
else if ( I am processor B ) then
multipy a matrix times a vector
end
</code></pre>
</p>
<p>
Another feature of <b>MPI</b> is that the data stored on each
computer is entirely separate from that stored on other computers.
If one computer needs data from another, or wants to send
a particular value to all the other computers, it must
explicitly call the appropriate library routine requesting
a data transfer. Depending on the library routine called,
it may be necessary for both sender and receiver to be
"on the line" at the same time (which means that one will
probably have to wait for the other to show up), or it is
possible for the sender to send the message to a buffer, for
later delivery, allowing the sender to proceed immediately
to further computation.
</p>
<p>
Here is a simple example of what a piece of the program would
look like, in which the number <b>X</b> is presumed to have been
computed by processor <b>A</b> and needed by processor <b>B</b>:
<pre><code>
if ( I am processor A ) then
call MPI_Send ( X )
else if ( I am processor B ) then
call MPI_Recv ( X )
end
</code></pre>
</p>
<p>
Often, an <b>MPI</b> program is written so that one computer
supervises the work, creating data, issuing it to the
worker computers, and gathering and printing the results at the
end. Other models are also possible.
</p>
<p>
It should be clear that a program using MPI to execute in parallel
will look much different from a corresponding sequential version.
The user must divide the problem data among the different processes,
rewrite the algorithm to divide up work among the processes,
and add explicit calls to transfer values as needed from the
process where a data item "lives" to a process that needs that
value.
</p>
<p>
A FORTRAN90 program, subroutine or function must include
the line
<pre><code>
use mpi
</code></pre>
so that the various MPI functions and constants are properly defined.
(If this <b>use</b> statement doesn't work, you may have to fall back
on using the FORTRAN77 include file instead:
<pre><code>
include "mpif.h"
</code></pre>
</p>
<p>
You probably compile and link your program with a single command,
as in
<pre><code>
f90 myprog.f90
</code></pre>
Depending on the computer that you are using, you may be able
to compile an MPI program with a similar command, which automatically
locates the include file and the compiled libraries that you will
need. This command is likely to be:
<pre><code>
mpif90 myprog.f90
</code></pre>
</p>
<h3 align = "center">
Interactive MPI Runs
</h3>
<p>
Some systems allow users to run an MPI program interactively.
You do this with the <b>mpirun</b> command:
<pre><code>
mpirun -np 4 a_output.txt
</code></pre>
This command requests that the executable program <i>a_output.txt</i>
be run, <i>right now</i>, using 4 processors.
</p>
<p>
The <b>mpirun</b> command may be a convenience for beginners,
with very small jobs, but this is not the way to go once you
have a large lengthy program to run! Also, what actually happens
can vary from machine to machine. When you ask for 4 processors,
for instance,
<ul>
<li>
in the best case, <b>mpirun</b> automatically finds three other
machines just like the one you are one, copies your program
to them, and starts your program on all four.
</li>
<li>
in a less good case, there are four processors on your current
machine, so the memory is divided up among them and your program
runs;
</li>
<li>
in a worse case, there are less than four processors available,
so, as necessary, one processor will "time share", and run two
or more of your processes alternately.
</li>
</ul>
</p>
<h3 align = "center">
Licensing:
</h3>
<p>
The computer code and data files described and made available on this web page
are distributed under
<a href = "../../txt/gnu_lgpl.txt">the GNU LGPL license.</a>
</p>
<h3 align = "center">
Languages:
</h3>
<p>
<b>MPI</b> examples are available in
<a href = "../../c_src/mpi/mpi.html">a C version</a> and
<a href = "../../cpp_src/mpi/mpi.html">a C++ version</a> and
<a href = "../../f77_src/mpi/mpi.html">a FORTRAN77 version</a> and
<a href = "../../f_src/mpi/mpi.html">a FORTRAN90 version</a>.
</p>
<h3 align = "center">
Related Data and Programs:
</h3>
<p>
<a href = "../../f_src/communicator_mpi/communicator_mpi.html">
COMMUNICATOR_MPI</a>,
a FORTRAN90 program which
creates new communicators involving a subset of initial
set of MPI processes in the default communicator MPI_COMM_WORLD.
</p>
<p>
<a href = "../../f_src/f90_calls_c_and_mpi/f90_calls_c_and_mpi.html">
F90_CALLS_C_AND_MPI</a>,
FORTRAN90 programs which
illustrate how a FORTRAN90 program can call a C function while
executing under the MPI parallel programming environment.
</p>
<p>
<a href = "../../f_src/f90_calls_c++_and_mpi/f90_calls_c++_and_mpi.html">
F90_CALLS_C++_AND_MPI</a>,
FORTRAN90 programs which
illustrate how a FORTRAN90 program can call a C++ function while
executing under the MPI parallel programming environment.
</p>
<p>
<a href = "../../f_src/heat_mpi/heat_mpi.html">
HEAT_MPI</a>,
a FORTRAN90 program which
solves the 1D Time Dependent Heat Equation using MPI.
</p>
<p>
<a href = "../../f_src/hello_mpi/hello_mpi.html">
HELLO_MPI</a>,
a FORTRAN90 program which
prints out "Hello, world!" using the MPI parallel programming environment.
</p>
<p>
<a href = "../../examples/moab/moab.html">
MOAB</a>,
examples which
illustrate the use of the MOAB job scheduler for a computer cluster.
</p>
<p>
<a href = "../../f_src/mpi_stubs/mpi_stubs.html">
MPI_STUBS</a>,
a FORTRAN90 library which
allows a user to compile, load, and possibly run an MPI program on a
serial machine.
</p>
<p>
<a href = "../../f_src/multitask_mpi/multitask_mpi.html">
MULTITASK_MPI</a>,
a FORTRAN90 program which
demonstrates how to "multitask", that is, to execute several unrelated
and distinct tasks simultaneously, using MPI for parallel execution.
</p>
<p>
<a href = "../../f_src/poisson_serial/poisson_serial.html">
POISSON_SERIAL</a>,
a FORTRAN90 program which
computes an approximate solution to the Poisson equation in a rectangle,
and is intended as the starting point for the creation of a parallel version.
</p>
<p>
<a href = "../../f_src/prime_mpi/prime_mpi.html">
PRIME_MPI</a>,
a FORTRAN90 program which
counts the number of primes between 1 and N, using MPI for parallel execution.
</p>
<p>
<a href = "../../c_src/pthreads/pthreads.html">
PTHREADS</a>,
C programs which
illustrate the use of the POSIX thread library to carry out
parallel program execution.
</p>
<p>
<a href = "../../f_src/quad_mpi/quad_mpi.html">
QUAD_MPI</a>,
a FORTRAN90 program which
approximates an integral using a quadrature rule, and carries out the
computation in parallel using MPI.
</p>
<p>
<a href = "../../f_src/random_mpi/random_mpi.html">
RANDOM_MPI</a>,
a FORTRAN90 program which
demonstrates one way to generate the same sequence of random numbers
for both sequential execution and parallel execution under MPI.
</p>
<p>
<a href = "../../f_src/ring_mpi/ring_mpi.html">
RING_MPI</a>,
a FORTRAN90 program which
uses the MPI parallel programming environment, and measures the time
necessary to copy a set of data around a ring of processes.
</p>
<p>
<a href = "../../f_src/satisfy_mpi/satisfy_mpi.html">
SATISFY_MPI</a>,
a FORTRAN90 program which
demonstrates, for a particular circuit, an exhaustive search
for solutions of the circuit satisfiability problem, using MPI to
carry out the calculation in parallel.
</p>
<p>
<a href = "../../f_src/search_mpi/search_mpi.html">
SEARCH_MPI</a>,
a FORTRAN90 program which
searches integers between A and B for a value J such that F(J) = C,
using MPI for parallel execution.
</p>
<p>
<a href = "../../f_src/task_division/task_division.html">
TASK_DIVISION</a>,
a FORTRAN90 library which
implements a simple procedure for smoothly dividing T tasks among
P processors; such a method can be useful in MPI and other parallel
environments, particularly when T is not an exact multiple of P,
and when the processors can be indexed starting from 0 or from 1.
</p>
<h3 align = "center">
Reference:
</h3>
<p>
<ol>
<li>
William Gropp, Steven Huss-Lederman, Andrew Lumsdaine, Ewing Lusk,
Bill Nitzberg, William Saphir, Marc Snir,<br>
MPI: The Complete Reference,<br>
Volume II: The MPI-2 Extensions,<br>
Second Edition,<br>
MIT Press, 1998,<br>
ISBN13: 978-0-262-57123-4,<br>
LC: QA76.642.M65.
</li>
<li>
William Gropp, Ewing Lusk, Anthony Skjellum,<br>
Using MPI: Portable Parallel Programming with the
Message-Passing Interface,<br>
Second Edition,<br>
MIT Press, 1999,<br>
ISBN: 0262571323,<br>
LC: QA76.642.G76.
</li>
<li>
William Gropp, Ewing Lusk, Rajiv Thakur,<br>
Using MPI-2: Advanced Features of the Message-Passing
Interface,<br>
Second Edition,<br>
MIT Press, 1999,<br>
ISBN: 0262571331,<br>
LC: QA76.642.G762.
</li>
<li>
Stan Openshaw, Ian Turton,<br>
High Performance Computing and the Art of Parallel Programming:
an Introduction for Geographers, Social Scientists, and
Engineers,<br>
Routledge, 2000,<br>
ISBN: 0415156920,<br>
LC: QA76.88.O64.
</li>
<li>
Peter Pacheco,<br>
Parallel Programming with MPI,<br>
Morgan Kaufman, 1996,<br>
ISBN: 1558603395,<br>
LC: QA76.642.P3.
</li>
<li>
Sudarshan Raghunathan,<br>
Making a Supercomputer Do What You Want: High Level Tools for
Parallel Programming,<br>
Computing in Science and Engineering,<br>
Volume 8, Number 5, September/October 2006, pages 70-80.
</li>
<li>
Marc Snir, Steve Otto, Steven Huss-Lederman, David Walker,
Jack Dongarra,<br>
MPI: The Complete Reference,<br>
Volume I: The MPI Core,<br>
Second Edition,<br>
MIT Press, 1998,<br>
ISBN: 0-262-69216-3,<br>
LC: QA76.642.M65.
</li>
<li>
Scott Vetter, Yukiya Aoyama, Jun Nakano,<br>
RS/600 SP: Practical MPI Programming,<br>
IBM Redbooks, 1999,<br>
ISBN: 0738413658.
</li>
</ol>
</p>
<h3 align = "center">
Examples and Tests:
</h3>
<p>
<b>BONES</b> passes a vector of real data from one process to
another. It was used as an introductory example in an MPI workshop.
<ul>
<li>
<a href = "bones_mpi.f90">bones_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "bones.sh">bones.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "bones_output.txt">bones_output.txt</a>,
the output file;
</li>
<li>
<a href = "bones_fsu.sh">bones_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "bones_fsu_output.txt">bones_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>BUFFON</b> demonstrates how parallel Monte Carlo
processes can set up distinct random number streams.
<ul>
<li>
<a href = "buffon_mpi.f90">buffon_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "buffon.sh">buffon.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "buffon_output.txt">
buffon_output.txt</a>,
the output file;
</li>
<li>
<a href = "buffon_fsu.sh">buffon_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "buffon_fsu_output.txt">buffon_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>DAY1</b> works out exercise #3 assigned after day 1 of a
workshop on MPI. The instructions were to have process 1 generate some
integers, send them to process 3 which used some of those values to
generate some real numbers which were then sent back to process 1.
<ul>
<li>
<a href = "day1_mpi.f90">day1_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "day1.sh">day1.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "day1_output.txt">day1_output.txt</a>,
the output file;
</li>
<li>
<a href = "day1_fsu.sh">day1_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "day1_fsu_output.txt">day1_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>INTERVALS</b> estimates an integral by dividing an interval
into subintervals, and having the servant processes estimate
the integral over each subinterval.
<ul>
<li>
<a href = "intervals_mpi.f90">intervals_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "intervals.sh">intervals.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "intervals_output.txt">intervals_output.txt</a>,
the output file;
</li>
<li>
<a href = "intervals_fsu.sh">intervals_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "intervals_fsu_output.txt">intervals_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>MATMAT</b> multiplies two matrices.
<ul>
<li>
<a href = "matmat_mpi.f90">matmat_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "matmat.sh">matmat.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "matmat_output.txt">matmat_output.txt</a>,
the output file;
</li>
<li>
<a href = "matmat_fsu.sh">matmat_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "matmat_fsu_output.txt">matmat_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>MATVEC</b> multiplies a matrix times a vector.
<ul>
<li>
<a href = "matvec_mpi.f90">matvec_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "matvec.sh">matvec.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "matvec_output.txt">matvec_output.txt</a>,
the output file;
</li>
<li>
<a href = "matvec_fsu.sh">matvec_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "matvec_fsu_output.txt">matvec_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>MONTE_CARLO</b> computes PI by the Monte Carlo method, testing
whether random points in the unit square are in the unit circle.
<ul>
<li>
<a href = "monte_carlo_mpi.f90">monte_carlo_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "monte_carlo.sh">monte_carlo.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "monte_carlo_output.txt">monte_carlo_output.txt</a>,
the output file;
</li>
<li>
<a href = "monte_carlo_fsu.sh">monte_carlo_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "monte_carlo_fsu_output.txt">monte_carlo_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>POISSON</b> solves Poisson's equation on a 2D grid,
dividing the physical region into horizontal strips, assigning
a process to each strip, and using MPI_SEND and MPI_RECV to
pass interface data between processes.
<ul>
<li>
<a href = "poisson_mpi.f90">poisson_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "poisson.sh">poisson.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "poisson_output.txt">poisson_output.txt</a>,
the output file;
</li>
<li>
<a href = "poisson_fsu.sh">poisson_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "poisson_fsu_output.txt">poisson_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>POISSON_NONBLOCK</b> is a revision to POISSON
which uses the nonblocking communication routines MPI_ISEND
and MPI_IRECV to pass interface data between processes.
<ul>
<li>
<a href = "poisson_nonblock_mpi.f90">poisson_nonblock_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "poisson_nonblock.sh">poisson_nonblock.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "poisson_nonblock_output.txt">poisson_nonblock_output.txt</a>,
the output file;
</li>
<li>
<a href = "poisson_nonblock_fsu.sh">poisson_nonblock_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "poisson_nonblock_fsu_output.txt">poisson_nonblock_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>QUADRATURE</b> estimates an integral.
<ul>
<li>
<a href = "quadrature_mpi.f90">quadrature_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "quadrature.sh">quadrature.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "quadrature_output.txt">quadrature_output.txt</a>,
the output file;
</li>
<li>
<a href = "quadrature_fsu.sh">quadrature_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "quadrature_fsu_output.txt">quadrature_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>SEARCH</b> searches a vector for occurrences of a particular
value.
<ul>
<li>
<a href = "search_mpi.f90">search_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "search.sh">search.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "search_output.txt">search_output.txt</a>,
the output file;
</li>
<li>
<a href = "search_fsu.sh">search_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "search_fsu_output.txt">search_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
<b>TYPE</b> demonstrates the use of a user-defined datatype.
<ul>
<li>
<a href = "type_mpi.f90">type_mpi.f90</a>,
the source code;
</li>
<li>
<a href = "type.sh">type.sh</a>,
a script to compile and run the program using MPIRUN.
</li>
<li>
<a href = "type_output.txt">type_output.txt</a>,
the output file;
</li>
<li>
<a href = "type_fsu.sh">type_fsu.sh</a>,
a script to compile and run the program on the FSU HPC cluster.
</li>
<li>
<a href = "type_fsu_output.txt">type_fsu_output.txt</a>,
the output file;
</li>
</ul>
</p>
<p>
You can go up one level to <a href = "../f_src.html">
the FORTRAN90 source codes</a>.
</p>
<hr>
<i>
Last revised on 23 October 2011.
</i>
<!-- John Burkardt -->
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