Difference between revisions of "Programming/C-Plusplus"

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== Programming Details ==
 
== Programming Details ==
  
C++ is a general-purpose, imperative computer programming language. It is derived from the the C language and shares many constructs with it, it also expands into object orientated pragramming paradigms.
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C++ is a general-purpose, imperative computer programming language. It is derived from the C language and shares many constructs with it, it also expands into object-orientated programming paradigms.
 
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{|
There is direct support for [[programming/OpenMP|openMP]] and [[programming/OpenMPI|openMPI]].
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|style="width:5%; border-width: 0;cellpadding=0" | [[File:icon_tick.png]]
 
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|style="width:95%; border-width: 0;cellpadding=0" | There is direct support for [[programming/OpenMP|openMP]] and [[programming/OpenMPI|openMPI]].
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|-
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|}
  
  
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     return 0;
 
     return 0;
 
}
 
}
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 +
</pre>
 +
 +
<pre style="background-color: #f5f5dc; color: black; font-family: monospace, sans-serif;">
 +
 +
#include <stdlib.h>
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#include <stdio.h>
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#include <omp.h>
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#include <iostream>
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#include <chrono>
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#include <vector>
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using namespace std;
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 +
#pragma optimize( "[t]", on)
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int main(int argc, char *argv[]){
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const int size = atoi(argv[1]);
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const int maxVal = 255;
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int row, col, ele;
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double** m1 =  new double*[size];
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double** m2 =  new double*[size];
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double** res =  new double*[size];
 +
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for (int i = 0; i < size; i++){
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m1[i] = new double[size];
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m2[i] = new double[size];
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res[i] = new double[size];
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}
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int procs = omp_get_num_procs();
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omp_set_num_threads(procs);
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std::chrono::duration<double, std::micro> time;
 +
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for (int row = 0; row < size; row++){
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for (int col = 0; col < size; col++){
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m1[row][col] = 0 + (rand() % maxVal);
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m2[row][col] = 0 + (rand() % maxVal);
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}
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}
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auto start = std::chrono::high_resolution_clock::now();
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#pragma omp parallel shared(m1, m2, res)
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{
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#pragma omp for nowait private(row, col, ele) schedule(dynamic)
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for (int row = 0; row < size; row++) {
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for (int ele = 0; ele < size; ele++){
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double temp = 0;
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for (int col = 0; col < size; col++){
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temp += m1[row][ele] * m2[ele][col];
 +
}
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res[row][col] += temp;
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}
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}
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}
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auto end = std::chrono::high_resolution_clock::now();
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time = end - start;
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cout << (time.count() / 1000 / 1000) << endl;
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 +
 +
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return 0;
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}
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 +
  
 
</pre>
 
</pre>
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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 load gcc/4.9.3
+
[username@login01 ~]$  module add gcc/8.2.0
 
[username@login01 ~]$  g++ -o test2 -fopenmp test2.c (openMP support)
 
[username@login01 ~]$  g++ -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)
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* module add intel/2018 (Intel compiler)
  
  
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== Usage Examples ==
 
== Usage Examples ==
  
== Batch example ==
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=== Batch example ===
 
 
  
 
<pre style="background-color: #C8C8C8; color: black; border: 2px solid #C8C8C8; font-family: monospace, sans-serif;">
 
<pre style="background-color: #C8C8C8; color: black; border: 2px solid #C8C8C8; font-family: monospace, sans-serif;">
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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 ==
+
== Next Steps ==
  
 
* [https://en.wikipedia.org/wiki/C%2B%2B https://en.wikipedia.org/wiki/C%2B%2B]
 
* [https://en.wikipedia.org/wiki/C%2B%2B https://en.wikipedia.org/wiki/C%2B%2B]
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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/]
  
[[Category:Programming]]
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{{Languagespagenav}}

Latest revision as of 15:29, 23 August 2023

Programming Details

C++ is a general-purpose, imperative computer programming language. It is derived from the C language and shares many constructs with it, it also expands into object-orientated programming paradigms.

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


Programming example


#include <omp.h>
#include <iostream> 

int main () 
{
    int thread_number;
    #pragma omp parallel private(thread_number)
    {
        #pragma omp for schedule(static) nowait
        for (int i = 0; i < 100; i++) 
        {
            thread_number = omp_get_thread_num();
            cout << "Thread " << thread_number << " says " << i << endl;
        }
    }
    return 0;
}


#include <stdlib.h>
#include <stdio.h>
#include <omp.h>
#include <iostream>
#include <chrono>
#include <vector>

using namespace std;

#pragma optimize( "[t]", on)
int main(int argc, char *argv[]){
	const int size = atoi(argv[1]);
	const int maxVal = 255;
	int row, col, ele;	
	
	double** m1 =  new double*[size];
	double** m2 =  new double*[size];
	double** res =  new double*[size];

	for (int i = 0; i < size; i++){
		m1[i] = new double[size];
		m2[i] = new double[size];
		res[i] = new double[size];
	}

	int procs = omp_get_num_procs();
	omp_set_num_threads(procs);

	std::chrono::duration<double, std::micro> time;	
	
	for (int row = 0; row < size; row++){
		for (int col = 0; col < size; col++){
			m1[row][col] = 0 + (rand() % maxVal);
			m2[row][col] = 0 + (rand() % maxVal);
		}
	}
	
	auto start = std::chrono::high_resolution_clock::now();

	#pragma omp parallel shared(m1, m2, res)
	{

		#pragma omp for nowait private(row, col, ele) schedule(dynamic)
		for (int row = 0; row < size; row++) {
			for (int ele = 0; ele < size; ele++){
				double temp = 0;
				for (int col = 0; col < size; col++){
					temp += m1[row][ele] * m2[ele][col];
				}
				res[row][col] += temp;
			}
		}
	}

	auto end = std::chrono::high_resolution_clock::now();
		

	time = end - start;
	
	cout << (time.count() / 1000 / 1000) << endl;

	

	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 ~]$  g++ -o test2 -fopenmp test2.c (openMP support)
[username@login01 ~]$ ./test2

Thread 22 says 32
Thread 11 says 39
.....

Modules Available

The following modules are available for C

  • module add gcc/8.2.0 (GNU compiler)
  • module add intel/2018 (Intel compiler)


Note: 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 234552

Next Steps





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