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// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
// SPDX-FileCopyrightText: Bradley M. Bell <bradbell@seanet.com>
// SPDX-FileContributor: 2003-24 Bradley M. Bell
// ----------------------------------------------------------------------------
/*
{xrst_begin a11c_sthread.cpp}
A Simple Boost Thread Example and Test
######################################
Purpose
*******
This example just demonstrates Boost threads and does not use CppAD at all.
Source Code
***********
{xrst_literal
// BEGIN C++
// END C++
}
{xrst_end a11c_sthread.cpp}
----------------------------------------------------------------------------
*/
// BEGIN C++
# include <thread>
# include <limits>
# include <cmath>
# include <cassert>
// for size_t
# include <cstddef>
//
# define NUMBER_THREADS 4
namespace { // Begin empty namespace
class worker_t
{
private:
int n_;
float* a_;
float* b_;
public:
void setup(size_t n, float* a, float* b)
{ n_ = static_cast<int>(n);
a_ = a;
b_ = b;
}
// Beginning of Example A.1.1.1c of OpenMP 2.5 standard document
void a1(int n, float *a, float *b)
{ int i;
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
void operator()()
{ a1(n_, a_, b_); }
};
}
bool a11c(void)
{ bool ok = true;
// Test setup
size_t 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
size_t number_threads = NUMBER_THREADS;
// set of workers
worker_t worker[NUMBER_THREADS];
// threads for each worker
std::thread* sthread[NUMBER_THREADS];
// Break the work up into sub work for each thread
size_t n = n_total / number_threads;
size_t n_tmp = n;
float* a_tmp = a;
float* b_tmp = b;
worker[0].setup(n_tmp, a_tmp, b_tmp);
for(j = 1; j < number_threads; j++)
{ n_tmp = n + 1;
a_tmp = a_tmp + n - 1;
b_tmp = b_tmp + n - 1;
if( j == (number_threads - 1) )
n_tmp = n_total - j * n + 1;
worker[j].setup(n_tmp, a_tmp, b_tmp);
// create this thread
sthread[j] = new std::thread(worker[j]);
}
// do this threads protion of the work
worker[0]();
// wait for other threads to finish
for(j = 1; j < number_threads; j++)
{ sthread[j]->join();
delete sthread[j];
sthread[j] = nullptr;
}
// check the result
float eps = 100.f * 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;
}
// END C++
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