# include <pthread.h>
# include <limits>
# include <cmath>
# include <cassert>

// define CPPAD_NULPTR
# include <cppad/configure.hpp>
# if CPPAD_USE_CPLUSPLUS_2011
# define CPPAD_NULL nullptr
# else
# define CPPAD_NULL 0
# endif
//
# define NUMBER_THREADS 4

# ifdef NDEBUG
# define CHECK_ZERO(expression) expression
# else
# define CHECK_ZERO(expression) assert( expression == 0 );
# endif
namespace {
     // Beginning of Example A.1.1.1c of OpenMP 2.5 standard document ---------
     void a1(int n, float *a, float *b)
     {     int i;
          // for some reason this function is missing on some systems
          // assert( pthread_is_multithreaded_np() > 0 );
          for(i = 1; i < n; i++)
               b[i] = (a[i] + a[i-1]) / 2.0f;
          return;
     }
     // End of Example A.1.1.1c of OpenMP 2.5 standard document ---------------
     struct start_arg { int  n; float* a; float* b; };
     void* start_routine(void* arg_vptr)
     {     start_arg* arg = static_cast<start_arg*>( arg_vptr );
          a1(arg->n, arg->a, arg->b);

          void* no_status = CPPAD_NULL;
          pthread_exit(no_status);

          return no_status;
     }
}

bool a11c(void)
{     bool ok = true;

     // Test setup
     int i, j, n_total = 10;
     float *a = new float[n_total];
     float *b = new float[n_total];
     for(i = 0; i < n_total; i++)
          a[i] = float(i);

     // number of threads
     int n_thread = NUMBER_THREADS;
     // the threads
     pthread_t thread[NUMBER_THREADS];
     // arguments to start_routine
     struct start_arg arg[NUMBER_THREADS];
     // attr
     pthread_attr_t attr;
     CHECK_ZERO( pthread_attr_init( &attr ) );
     CHECK_ZERO( pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE) );
     //
     // Break the work up into sub work for each thread
     int n = n_total / n_thread;
     arg[0].n = n;
     arg[0].a = a;
     arg[0].b = b;
     for(j = 1; j < n_thread; j++)
     {     arg[j].n = n + 1;
          arg[j].a = arg[j-1].a + n - 1;
          arg[j].b = arg[j-1].b + n - 1;
          if( j == (n_thread - 1) )
               arg[j].n = n_total - j * n + 1;
     }
     for(j = 0; j < n_thread; j++)
     {     // inform each thread of which block it is working on
          void* arg_vptr = static_cast<void*>( &arg[j] );
          CHECK_ZERO( pthread_create(
               &thread[j], &attr, start_routine, arg_vptr
          ) );
     }
     for(j = 0; j < n_thread; j++)
     {     void* no_status = CPPAD_NULL;
          CHECK_ZERO( pthread_join(thread[j], &no_status) );
     }

     // check the result
     float eps = 100.0f * std::numeric_limits<float>::epsilon();
     for(i = 1; i < n ; i++)
          ok &= std::fabs( (2. * b[i] - a[i] - a[i-1]) / b[i] ) <= eps;

     delete [] a;
     delete [] b;

     return ok;
}