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4e94cab681
This improves the monte carlo example by using the count_if() algorithm instead of a custom kernel with atomics. Also includes only the required headers instead of all the Boost.Compute headers.
69 lines
2.3 KiB
C++
69 lines
2.3 KiB
C++
//---------------------------------------------------------------------------//
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// Copyright (c) 2013 Kyle Lutz <kyle.r.lutz@gmail.com>
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//
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// Distributed under the Boost Software License, Version 1.0
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// See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt
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//
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// See http://kylelutz.github.com/compute for more information.
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//---------------------------------------------------------------------------//
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#include <iostream>
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#include <boost/compute/function.hpp>
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#include <boost/compute/system.hpp>
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#include <boost/compute/algorithm/count_if.hpp>
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#include <boost/compute/container/vector.hpp>
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#include <boost/compute/iterator/buffer_iterator.hpp>
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#include <boost/compute/random/default_random_engine.hpp>
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#include <boost/compute/types/builtin.hpp>
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namespace compute = boost::compute;
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int main()
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{
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// get default device and setup context
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compute::device gpu = compute::system::default_device();
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compute::context context(gpu);
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compute::command_queue queue(context, gpu);
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std::cout << "device: " << gpu.name() << std::endl;
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using compute::uint_;
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using compute::uint2_;
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// ten million random points
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size_t n = 10000000;
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// generate random numbers
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compute::default_random_engine rng(context);
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compute::vector<uint_> vector(n * 2, context);
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rng.fill(vector.begin(), vector.end(), queue);
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// function returing true if the point is within the unit circle
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BOOST_COMPUTE_FUNCTION(bool, is_in_unit_circle, (uint2_),
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{
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const float x = _1.x / (float) UINT_MAX - 1;
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const float y = _1.y / (float) UINT_MAX - 1;
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return (x*x + y*y) < 1.0f;
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});
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// iterate over vector<uint> as vector<uint2>
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compute::buffer_iterator<uint2_> start =
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compute::make_buffer_iterator<uint2_>(vector.get_buffer(), 0);
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compute::buffer_iterator<uint2_> end =
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compute::make_buffer_iterator<uint2_>(vector.get_buffer(), vector.size() / 2);
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// count number of random points within the unit circle
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size_t count = compute::count_if(start, end, is_in_unit_circle, queue);
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// print out values
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float count_f = static_cast<float>(count);
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std::cout << "count: " << count << " / " << n << std::endl;
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std::cout << "ratio: " << count_f / float(n) << std::endl;
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std::cout << "pi = " << (count_f / float(n)) * 4.0f << std::endl;
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return 0;
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}
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