Example8

Purpose

C++ code example on the FASRC cluster. function_factorial.cpp shows how to do recursion.

Since this code reads an input from the command line, it cannot be run as a batch job and only as an interactive job.

Contents

• function_factorial.cpp: c++ source code

C++ code

/*
  Program: function_factorial.cpp
           Calculates factorial of a number (e.g., 10! )
 */
#include <iostream>
#include <string>
#include <sstream>
#include <cmath>
#include <iomanip>
using namespace std;

#define XTAB '\t'

// Factorial function prototype.............................
long factorial( long a );

// Main program.............................................
int main(){
  long i;
  long n;
  string s;
  long r;
  stringstream ss;
  cout << "Please type an integer: ";
  getline(cin,s);
  ss.clear();
  ss << s;
  ss >> n;
  for ( i = 1 ; i <= n; i++ ){
    r = factorial(i);
    cout << i << XTAB << r << endl;
  }
  return 0;
}

// Factorial function.......................................
long factorial( long a ){
  long r;
  if ( a > 1 ){
    r = a * factorial( a - 1 );
    return( r );
  }
  else{
    return(1);
  }
}

Compile

We recommend compiling on a compute node. Request an interactive job to use a compute node, e.g.,

salloc --partition test --time 00:30:00 -c 2 --mem-per-cpu 2G

• Intel compilers, e.g.,

module load intel
icpc -O2 -o function_factorial.x function_factorial.cpp  # for intel version < 23.2, use `icpc`
icpx -O2 -o function_factorial.x function_factorial.cpp  # for intel version >= 23.2, use `icpx`.

• GNU compilers, e.g.,

module load gcc
g++ -O2 -o function_factorial.x function_factorial.cpp

Run interactive code

On a compute node

./function_factorial.x

Example output

Please type an integer: 10
1	1
2	2
3	6
4	24
5	120
6	720
7	5040
8	40320
9	362880
10	3628800