triad.cpp

/*
Created by Marc Bolinches
*/

#include <iostream>
#include <string>
#include <stdlib.h>
#include <fstream>
#include <mpi.h>

#ifdef _DOUBLE_
#define Ffloat double
#else
#define Ffloat float
#endif

void copy2file(Ffloat *a, int N);

using namespace std;

int main(int narg, char **argv)
{
  // initialize variables
  size_t Narray = 1;

  // mpi vars
  int rank, worldSize;
  MPI_Init(&narg, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &rank);
  MPI_Comm_size(MPI_COMM_WORLD, &worldSize);

  // read imput
  if( narg < 2)
  {
    cout<< "Wrong number of arguments. Use as follows: " << endl;
    cout<< "    triad.p arrayLength " << endl;
    cout<< "where " << std::endl;
    cout << "  arrayLength is the length of the array to be used" << endl;
    return 1;
  }else 
  {
    Narray = stoi(argv[1]);
  }

  // create and allocate arrays
  Ffloat *a  = new Ffloat[Narray];
  Ffloat *b  = new Ffloat[Narray];
  Ffloat *c  = new Ffloat[Narray];
  Ffloat *d  = new Ffloat[Narray];

  // initialize arrays
  for( size_t i = 0; i < Narray; i++)
  {
    a[i] = rand();
    b[i] = rand();
    c[i] = rand();
    d[i] = rand();
  }

  // repeat excercise "repeat" times and average times
  int repeat = 20;
  double avgTime = 0.;
  for(int n = 0; n < repeat; n++)
  {
    double time = MPI_Wtime();
    
    // operations that need to be measured
    for( size_t i = 0; i < Narray; i++)
    {
      a[i] = b[i] + c[i]*d[i];
    }

    avgTime += MPI_Wtime() - time;

    copy2file(a, Narray);

    // change arrays
    for( size_t i = 0; i < Narray; i++)
    {
      a[i] = rand();
      b[i] = rand();
      c[i] = rand();
      d[i] = rand();
    }
  }

  avgTime /= double(repeat);

  if( rank == 0 )
    cout << "GFlops/sec " << 2.*double(Narray)/avgTime*1e-6 << endl;

  delete[] a, b, c, d;

  MPI_Finalize();
  return 0;
}


/*
Auxiliary functions
*/
void copy2file(Ffloat *a, int N)
{
  ofstream file;
  file.open("dummyFile.txt");
  
  for(int i = 0; i < N; i++)
  {
    file << a[i] << endl;
  }

  file.close();
}