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<center><b><big><big>A Simple Parallel Pthread Example and Test</big></big></b></center>
<br/>
<b><big><a name="Purpose" id="Purpose">Purpose</a></big></b>
<br/>
This example just demonstrates pthreads and does not use CppAD at all.

<br/>
<br/>
<b><big><a name="Source Code" id="Source Code">Source Code</a></big></b>

<code><font color="blue">
<br/>
<pre style='display:inline'> 
# include &lt;pthread.h&gt;
# include &lt;limits&gt;
# include &lt;cmath&gt;
# include &lt;cassert&gt;

// define CPPAD_NULPTR
# include &lt;cppad/configure.hpp&gt;
# if CPPAD_HAS_NULLPTR
# 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() &gt; 0 );
		for(i = 1; i &lt; n; i++) 
			b[i] = (a[i] + a[i-1]) / 2.0;
		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&lt;start_arg*&gt;( arg_vptr );
		a1(arg-&gt;n, arg-&gt;a, arg-&gt;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 &lt; 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( &amp;attr ) );
	CHECK_ZERO( pthread_attr_setdetachstate(&amp;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 &lt; 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 &lt; n_thread; j++)
	{	// inform each thread of which block it is working on
		void* arg_vptr = static_cast&lt;void*&gt;( &amp;arg[j] );
		CHECK_ZERO( pthread_create(
			&amp;thread[j], &amp;attr, start_routine, arg_vptr
		) );
	}
	for(j = 0; j &lt; n_thread; j++)
	{	void* no_status = CPPAD_NULL;
		CHECK_ZERO( pthread_join(thread[j], &amp;no_status) );
	}

	// check the result
	float eps = 100. * std::numeric_limits&lt;float&gt;::epsilon();
	for(i = 1; i &lt; n ; i++)
		ok &amp;= std::fabs( (2. * b[i] - a[i] - a[i-1]) / b[i] ) &lt;= eps; 

	delete [] a;
	delete [] b;

	return ok;
}
</pre>

</font></code>

<hr/>Input File: multi_thread/pthread/a11c_pthread.cpp

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