Difference between revisions of "Programming/C"

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== Programming Details ==
 
== Programming Details ==
  
C is a general-purpose, imperative computer programming language. There are some derivations of the language due to the modernisation of the original specification in the form of C++ and C#.
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C is a general-purpose, imperative computer programming language. There are some derivations of the language due to the modernization of the original specification in the form of C++ and C#.
 
{|
 
{|
 
|style="width:5%; border-width: 0;cellpadding=0" | [[File:icon_tick.png]]
 
|style="width:5%; border-width: 0;cellpadding=0" | [[File:icon_tick.png]]
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<pre style="background-color: black; color: white; border: 2px solid black; font-family: monospace, sans-serif;">
 
<pre style="background-color: black; color: white; border: 2px solid black; font-family: monospace, sans-serif;">
[username@login01 ~]$  module add gcc/4.9.3
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[username@login01 ~]$  module add gcc/8.2.0
 
[username@login01 ~]$  gcc -o test2 -fopenmp test2.c (openMP support)
 
[username@login01 ~]$  gcc -o test2 -fopenmp test2.c (openMP support)
 
[username@login01 ~]$ ./test2
 
[username@login01 ~]$ ./test2
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The following modules are available for C
 
The following modules are available for C
  
* module add gcc/4.9.3 (GNU compiler)
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* module add gcc/8.2.0 (GNU compiler)
 
* module add intel/compiler/64/2016.2.181 (Intel compiler)
 
* module add intel/compiler/64/2016.2.181 (Intel compiler)
 
{|
 
{|
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#SBATCH -p compute
 
#SBATCH -p compute
 
#SBATCH --exclusive
 
#SBATCH --exclusive
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#SBATCH --mail-user= your email address here
  
 
echo $SLURM_JOB_NODELIST
 
echo $SLURM_JOB_NODELIST
  
 
module purge
 
module purge
module add gcc/4.9.3
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module add gcc/8.2.0
  
 
export I_MPI_DEBUG=5
 
export I_MPI_DEBUG=5
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</pre>
 
</pre>
  
== Further Information ==
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== Next Steps ==
  
 
* [https://en.wikipedia.org/wiki/C_(programming_language) https://en.wikipedia.org/wiki/C_(programming_language)]
 
* [https://en.wikipedia.org/wiki/C_(programming_language) https://en.wikipedia.org/wiki/C_(programming_language)]
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* [https://computing.llnl.gov/tutorials/openMP/ https://computing.llnl.gov/tutorials/openMP/]
 
* [https://computing.llnl.gov/tutorials/openMP/ https://computing.llnl.gov/tutorials/openMP/]
  
[[Programming|Programming support]]
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{{Languagespagenav}}

Latest revision as of 11:25, 16 November 2022

Programming Details

C is a general-purpose, imperative computer programming language. There are some derivations of the language due to the modernization of the original specification in the form of C++ and C#.

Icon tick.png There is direct support for openMP and openMPI.

Programming example


#include <omp.h>
#include <stdio.h>

int main (int argc, char *argv[]){
        int nthreads, tid;

        /* Fork a team of threads giving them their own copies of variables*/
        #pragma omp parallel
        {
                /* Obtain thread number */
                tid = omp_get_thread_num();
                printf("Hello World from thread = %d\n", tid);

                /* Only Master thread does this */
                if(tid == 0)
                {
                        nthreads = omp_get_num_threads();
                        printf("Number of threads = %d\n", nthreads);
                }

        }       /* All threads join together and disband */

        return (0);
}


Compilation

The program would be compiled in the following way, optional Intel compiler available too:


[username@login01 ~]$  module add gcc/8.2.0
[username@login01 ~]$  gcc -o test2 -fopenmp test2.c (openMP support)
[username@login01 ~]$ ./test2

Hello World from thread = 0
Number of threads = 1

Modules Available

The following modules are available for C

  • module add gcc/8.2.0 (GNU compiler)
  • module add intel/compiler/64/2016.2.181 (Intel compiler)
Icon exclam3.png OpenMP is a library directive within the compiler and does not require any additional module to be loaded.

Usage Examples

Batch example


#!/bin/bash

#SBATCH -J openmpi-single-node
#SBATCH -N 1
#SBATCH --ntasks-per-node 28
#SBATCH -o %N.%j.%a.out
#SBATCH -e %N.%j.%a.err
#SBATCH -p compute
#SBATCH --exclusive
#SBATCH --mail-user= your email address here

echo $SLURM_JOB_NODELIST

module purge
module add gcc/8.2.0

export I_MPI_DEBUG=5
export I_MPI_FABRICS=shm:tmi
export I_MPI_FALLBACK=no

/home/user/CODE_SAMPLES/OPENMP/demo


[username@login01 ~]$ sbatch demo.job
Submitted batch job 289552

Next Steps





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