# 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 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];
//
//  Set X to random values.
//
  for ( i = 0; i < n; i++ )
  {
    x[i] =  ( float ) rand ( ) / ( float ) RAND_MAX;
  }
//
//  Compute the l1 norm sequentially.
//
  wtime1 = omp_get_wtime ( );
  x_l1_norm = 0.0;
  for ( i = 0; i < n; i++ )
  {
    x_l1_norm = x_l1_norm + fabs ( x[i] );
  }
  wtime2 = omp_get_wtime ( );
  wtime = wtime2 - wtime1;

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

  cout << "\n";
  cout << "Parallel calculation:\n";
  cout << "  L1_NORM = " << x_l1_norm << "\n";
  cout << "  Time =    " << wtime << "\n";

  delete [] x;

  return 0;
}