# include <stdlib.h>
# include <stdio.h>
# include <math.h>
# include <time.h>
# include <omp.h>

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

/******************************************************************************/

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

/******************************************************************************/
/*
  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 ( );
}
  printf ( "\n" );
  printf ( "L1_NORM:\n" );
  printf ( "  C version\n" );
  printf ( "  Number of threads is %d\n", num_threads );

  x = ( float * ) malloc ( n * sizeof ( float ) );
/*
  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;

  printf ( "\n" );
  printf ( "Sequential calculation:\n" );
  printf ( "  L1_NORM = %f\n", x_l1_norm );
  printf ( "  Time =    %f\n", wtime );
/*
  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;

  printf ( "\n" );
  printf ( "Parallel calculation:\n" );
  printf ( "  L1_NORM = %f\n", x_l1_norm );
  printf ( "  Time =    %f\n", wtime );

  free ( x );

  return 0;
}