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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"><head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" /> <style type="text/css"> body { font-family: Verdana, Arial, Helvetica, sans-serif;} a.at-term { font-style: italic; } </style> <title>Adding MPI to C and Fortran Programs (cont.)</title> <meta name="Generator" content="ATutor"> <meta name="Keywords" content=""></head><body> <p>So far we have covered how to initialize MPI in a C or Fortran program and how to call several fundamental routines which return information about the MPI environment. The last function call that is required is MPI_Finalize,
which is called by every process once you are finished using MPI. Once MPI_Finalize is called, no further calls to the MPI library may be made.</p>
<h3>Exiting MPI</h3>
<p>This must be the last MPI call made. It is collective and must be made by "all" processes.</p>
<p class="codelang">
C:</p>
<pre><code>MPI_Finalize()</code></pre>
<p class="codelang">
Fortran:</p>
<pre><code>CALL MPI_FINALIZE(IERROR)</code></pre>
<p>The material that has just been covered will be used in almost every MPI program that you will write. As such, it is convenient to place these statements into a skeleton program that can act as a template when we want to create new MPI programs.</p>
<h4>Bones.c</h4>
<pre><code>#include <mpi.h>
int main(int argc, char *argv[]) {
int rank, size;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
/* your code here */
MPI_Finalize();
}
</code></pre>
<h4>Bones.f</h4>
<pre><code> PROGRAM skeleton
INCLUDE 'mpif.h'
INTEGER ierror, rank, size
CALL MPI_INIT(ierror)
CALL MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierror)
CALL MPI_COMM_SIZE(MPI_COMM_WORLD, size, ierror)
C your code here
CALL MPI_FINALIZE(ierror)
END
</code></pre>
<h3>A Programming Classic - Hello World</h3>
<p>No programming training material would be complete without the classic <em>Hello World</em> application. Here we can use the "Bones" templates assembled in the previous section as a starting point.</p>
<p>We will design a program that will run with 3 or more processes. The process with identifier, or <em>rank</em>, of 2 will print out the phrase "Hello world!". All processes in the communicator will print out their rank and the size of the default communicator, MPI_COMM_WORLD.</p>
<p class="codelang">C:</p>
<pre><code>#include <mpi.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
int rank,size;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
if(rank==2) printf ("P:%d Hello world!\n",rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
printf("I am %d out of %d.\n", rank, size);
MPI_Finalize();
}</code></pre>
<p class="codelang">
Fortran:
</p>
<pre><code> PROGRAM hello
INCLUDE 'mpif.h'
INTEGER ierror, rank, size
CALL MPI_INIT(ierror)
CALL MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierror)
CALL MPI_COMM_SIZE(MPI_COMM_WORLD, size, ierror)
if(rank.eq.2) print *,'P:',rank,' Hello World'
print *,'I have rank ',rank,' out of ',size
CALL MPI_FINALIZE(ierror)
END</code></pre></body></html>⌨️ 快捷键说明
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