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- //---------------------------------------------------------------------------//
- // Copyright (c) 2013-2014 Kyle Lutz <kyle.r.lutz@gmail.com>
- //
- // Distributed under the Boost Software License, Version 1.0
- // See accompanying file LICENSE_1_0.txt or copy at
- // http://www.boost.org/LICENSE_1_0.txt
- //
- // See http://boostorg.github.com/compute for more information.
- //---------------------------------------------------------------------------//
- #include <iostream>
- #include <opencv2/core/core.hpp>
- #include <opencv2/highgui/highgui.hpp>
- #include <opencv2/imgproc/imgproc.hpp>
- #include <boost/compute/system.hpp>
- #include <boost/compute/algorithm/inclusive_scan.hpp>
- #include <boost/compute/algorithm/inclusive_scan.hpp>
- #include <boost/compute/interop/opencv/core.hpp>
- #include <boost/compute/interop/opencv/highgui.hpp>
- #include <boost/compute/random/default_random_engine.hpp>
- #include <boost/compute/random/uniform_real_distribution.hpp>
- #include <boost/compute/utility/source.hpp>
- namespace compute = boost::compute;
- // this example uses the random-number generation functions in Boost.Compute
- // to calculate a large number of random "steps" and then plots the final
- // random "walk" in a 2D image on the GPU and displays it with OpenCV
- int main()
- {
- // number of random steps to take
- size_t steps = 250000;
- // height and width of image
- size_t height = 800;
- size_t width = 800;
- // get default device and setup context
- compute::device gpu = compute::system::default_device();
- compute::context context(gpu);
- compute::command_queue queue(context, gpu);
- using compute::int2_;
- // calaculate random values for each step
- compute::vector<float> random_values(steps, context);
- compute::default_random_engine random_engine(queue);
- compute::uniform_real_distribution<float> random_distribution(0.f, 4.f);
- random_distribution.generate(
- random_values.begin(), random_values.end(), random_engine, queue
- );
- // calaculate coordinates for each step
- compute::vector<int2_> coordinates(steps, context);
- // function to convert random values to random directions (in 2D)
- BOOST_COMPUTE_FUNCTION(int2_, take_step, (const float x),
- {
- if(x < 1.f){
- // move right
- return (int2)(1, 0);
- }
- if(x < 2.f){
- // move up
- return (int2)(0, 1);
- }
- if(x < 3.f){
- // move left
- return (int2)(-1, 0);
- }
- else {
- // move down
- return (int2)(0, -1);
- }
- });
- // transform the random values into random steps
- compute::transform(
- random_values.begin(), random_values.end(), coordinates.begin(), take_step, queue
- );
- // set staring position
- int2_ starting_position(width / 2, height / 2);
- compute::copy_n(&starting_position, 1, coordinates.begin(), queue);
- // scan steps to calculate position after each step
- compute::inclusive_scan(
- coordinates.begin(), coordinates.end(), coordinates.begin(), queue
- );
- // create output image
- compute::image2d image(
- context, width, height, compute::image_format(CL_RGBA, CL_UNSIGNED_INT8)
- );
- // program with two kernels, one to fill the image with white, and then
- // one the draw to points calculated in coordinates on the image
- const char draw_walk_source[] = BOOST_COMPUTE_STRINGIZE_SOURCE(
- __kernel void draw_walk(__global const int2 *coordinates,
- __write_only image2d_t image)
- {
- const uint i = get_global_id(0);
- const int2 coord = coordinates[i];
- if(coord.x > 0 && coord.x < get_image_width(image) &&
- coord.y > 0 && coord.y < get_image_height(image)){
- uint4 black = { 0, 0, 0, 0 };
- write_imageui(image, coord, black);
- }
- }
- __kernel void fill_white(__write_only image2d_t image)
- {
- const int2 coord = { get_global_id(0), get_global_id(1) };
- if(coord.x < get_image_width(image) &&
- coord.y < get_image_height(image)){
- uint4 white = { 255, 255, 255, 255 };
- write_imageui(image, coord, white);
- }
- }
- );
- // build the program
- compute::program draw_program =
- compute::program::build_with_source(draw_walk_source, context);
- // fill image with white
- compute::kernel fill_kernel(draw_program, "fill_white");
- fill_kernel.set_arg(0, image);
- const size_t offset[] = { 0, 0 };
- const size_t bounds[] = { width, height };
- queue.enqueue_nd_range_kernel(fill_kernel, 2, offset, bounds, 0);
- // draw random walk
- compute::kernel draw_kernel(draw_program, "draw_walk");
- draw_kernel.set_arg(0, coordinates);
- draw_kernel.set_arg(1, image);
- queue.enqueue_1d_range_kernel(draw_kernel, 0, coordinates.size(), 0);
- // show image
- compute::opencv_imshow("random walk", image, queue);
- // wait and return
- cv::waitKey(0);
- return 0;
- }
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