# include <cstdlib>
# include <iostream>
# include <cmath>
# include <ctime>
# include <omp.h>

using namespace std;

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

//****************************************************************************80

int main ( int argc, char *argv[] )

//****************************************************************************80
//
//  Purpose:
//
//    MAIN is the main program for L1_NORM.
//
{
  int i;
  int j;
  int num_threads;
  int n = 1000;
  double wtime;
  double wtime1;
  double wtime2;
  float *x;
  float *x_l1_norm;

# pragma omp parallel
{
  num_threads = omp_get_num_threads ( );
}
  cout << "\n";
  cout << "L1_NORM:\n";
  cout << "  C++ version\n";
  cout << "  Number of threads is " << num_threads << "\n";

  x = new float[n*n];
//
//  Set X to random values.
//
  for ( j = 0; j < n; j++ )
  {
    for ( i = 0; i < n; i++ )
    {
      x[i+j*n] =  ( float ) rand ( ) / ( float ) RAND_MAX;
    }
  }

  x_l1_norm = new float[n];
//
//  Compute the l1 norm sequentially.
//
  wtime1 = omp_get_wtime ( );
  for ( j = 0; j < n; j++ )
  {
    x_l1_norm[j] = 0.0;
    for ( i = 0; i < n; i++ )
    {
      x_l1_norm[j] = x_l1_norm[j] + fabs ( x[i+j*n] );
    }
  }
  wtime2 = omp_get_wtime ( );
  wtime = wtime2 - wtime1;

  cout << "\n";
  cout << "Sequential calculation:\n";
  cout << "  L1_NORM (first 4 ) = " 
       << "  " << x_l1_norm[0]
       << "  " << x_l1_norm[1]
       << "  " << x_l1_norm[2]
       << "  " << x_l1_norm[3] << "\n";
  cout << "  Time =    " << wtime << "\n";
//
//  Compute the l1 norm in parallel.
//
  wtime1 = omp_get_wtime ( );
# pragma omp parallel private ( i, j ) shared ( n, x, x_l1_norm )
# pragma omp for
  for ( j = 0; j < n; j++ )
  {
    x_l1_norm[j] = 0.0;
    for ( i = 0; i < n; i++ )
    {
      x_l1_norm[j] = x_l1_norm[j] + fabs ( x[i+j*n] );
    }
  }
  wtime2 = omp_get_wtime ( );
  wtime = wtime2 - wtime1;

  cout << "\n";
  cout << "Parallel calculation:\n";
  cout << "  L1_NORM (first 4 ) = " 
       << "  " << x_l1_norm[0]
       << "  " << x_l1_norm[1]
       << "  " << x_l1_norm[2]
       << "  " << x_l1_norm[3] << "\n";
  cout << "  Time =    " << wtime << "\n";

  delete [] x;
  delete [] x_l1_norm;

  return 0;
}