======Compiling======
=====Compilers=====
The following is a list of C, C++ and Fortran compilers available on the CHPC cluster:
====Intel====
  * ''icc'' (for C and C++)
  * ''ifort''
====GNU Compiler Collection====
  * ''gcc''
  * ''g++''
  * ''gfortran''

=====Environment=====
====module Command====
The module command provides a convenient mechanism for managing which environment variables are set in your shell session. The following is a list of the basic usage of the module command:
  * Check which modules are available <code>module avail</code>
  * Add a module to the current environment <code>module add <module></code>
  * Show loaded modules <code>module list</code>
  * Remove a module from the environment <code>module remove <module></code> or <code>module rm <module></code>


=====Compiling=====
====Example Code====
===C===
<code c>
#include <stdio.h>

int main()
{
    printf("Hello World");
    return 0;
}
</code>
===C with MPI===
<code c>
#include <stdlib.h>
#include <stdio.h>
#include <mpi.h>

int
main(argc, argv)

int                     argc;
char                    *argv[];

{
        int             rank, size, len;
        char            name[MPI_MAX_PROCESSOR_NAME];

        MPI_Init(&argc, &argv);
        MPI_Comm_rank(MPI_COMM_WORLD, &rank);
        MPI_Comm_size(MPI_COMM_WORLD, &size);

        MPI_Get_processor_name(name, &len);
        printf ("Hello world! I'm %d of %d on %s\n", rank, size, name);

        MPI_Finalize();
        exit(0);
}
</code>
===Fortran===
<code fortran>
PROGRAM Hello
    PRINT *, "Hello World"
END PROGRAM Hello
</code>
====GNU====
The following code snippets demonstrate how to compile the above code examples use the GNU compiler suite:
===C===
<code>gcc -o hello hello.c</code>
===C with MPI===
<code>mpicc -o hello hello.c</code>

===Fortran===
<code>gfortran -o hello hello.f90</code>

=====OpenMP=====
The above compilers include support for OpenMP.  To compile an OpenMP code add the ''-fopenmp'' option.  For example:
<code>gcc -o mp_hello -fopenmp mp_hello.c</code>

code from https://computing.llnl.gov/tutorials/openMP/samples/C/omp_hello.c
====Intel Compilers====
The following code snippets demonstrate how to compile OpenMP examples with the Intel compilers:
===C===
<code>icc -openmp omp_hello.c -o hello</code>
===Fortran===
<code>ifort -openmp omp_hello.f -o hello</code>

===Java===

An example of compiling and executing a simple Java program:
====MyFirstJavaProgram.java====
<code> 
public class MyFirstJavaProgram {
  public static void main(String []args) {
    System.out.println("Hello World"); // prints Hello World
  }
}
</code>

To compile this, make sure you have the java module loaded, then:
<code>
javac MyFirstJavaProgram.java</code>

A bytecode-compiled file should be created, named MyFirstJavaProgram.class

To execute it, run as follows:
<code>
java MyFirstJavaProgram
</code>
=====MPI=====
MPI (Message Passing Interface -- [[http://www.open-mpi.org]]) is provided using the OpenMPI libraries.  To compile MPI code use the ''mpicc'' or ''mpif90'' compilers.

To run an MPI job see the man pages for PBS Pro. On the login node, type "man qsub". To obtain an interactive node,
use ''qsub -I'' The login node prevents long-running processes therefore an interactive node is useful for compilations and builds. To test your code, load the module you want to use first, and then compile your code with it:

''$mpicc -o bin/test src/hello_world.c''

To test it:

<code>mpirun -np 8 bin/test</code>

You should see something similar to:
<code>
Hello world! I'm 7 of 8 on cnode-2-6
Hello world! I'm 6 of 8 on cnode-2-6
Hello world! I'm 5 of 8 on cnode-2-6
Hello world! I'm 1 of 8 on cnode-2-6
Hello world! I'm 0 of 8 on cnode-2-6
Hello world! I'm 3 of 8 on cnode-2-6
Hello world! I'm 2 of 8 on cnode-2-6
Hello world! I'm 4 of 8 on cnode-2-6
</code>