University:
Boston University
Course:
CAS CS 320 | Concepts of Programming Languages
Academic year:

2023
Views:

219

Pages:

9
Author:

daudaunis11

GPU Computing with CUDA Lab 5 - Thrust Objectives ‣ Experiment with Thrust ‣ Outline - Walk through various examples - Implement “weld triangles” example Thrust - Example 1 #include #include #include int main(void) { thrust::device_vector data(4); data[0] data[1] data[2] data[3] = = = = 10; 20; 30; 40; int sum = thrust::reduce(data.begin(), data.end()); std::cout << "sum is " << sum << std::endl; return 0; } Thrust - Example 2 #include #include struct triple { __host__ __device__ int operator()(int x) { return 3 * x; } }; int main(void) { thrust::device_vector input(4); input[0] = 10; input[1] = 20; input[2] = 30; input[3] = 40; thrust::device_vector output(4); thrust::transform(input.begin(), input.end(), output.begin(), triple()); for (int i = 0; i < output.size(); i++) std::cout << output[i] << std::endl; return 0; } Thrust - Example 3 #include #include #include int main(void) { thrust::device_vector data(8); data[0] = 6; data[1] = 3; data[2] = 7; data[3] = 5; data[4] = 9; data[5] = 0; data[6] = 8; data[7] = 1; thrust::sort(data.begin(), data.end()); std::cout << "ascending" << std::endl; for (int i = 0; i < data.size(); i++) std::cout << data[i] << std::endl; thrust::sort(data.begin(), data.end(), thrust::greater()); std::cout << "descending" << std::endl; for (int i = 0; i < data.size(); i++) std::cout << data[i] << std::endl; return 0; } Thrust - Example 4 #include #include #include struct is_odd { __host__ __device__ bool operator()(int x) { return (x % 2) == 1; } }; int main(void) { thrust::device_vector data(8); data[0] = 6; data[1] = 3; data[2] = 7; data[3] = 5; data[4] = 9; data[5] = 0; data[6] = 8; data[7] = 1; int N = thrust::count_if(data.begin(), data.end(), is_odd()); std::cout << "counted " << N << " odd values" << std::endl; thrust::device_vector odds(N); thrust::copy_if(data.begin(), data.end(), odds.begin(), is_odd()); for (int i = 0; i < odds.size(); i++) std::cout << odds[i] << std::endl; return 0; } Thrust - Example 5 #include #include #include #include int main(void) { int N = 100000; thrust::host_vector h_data(N); thrust::device_vector d_data(N); // // // // method 1: (one cudaMemcpy per element) for (int i = 0; i < N; i++) d_data[i] = i; // // // // // // method 2: one cudaMemcpy for entire array for (int i = 0; i < N; i++) h_data[i] = i; thrust::copy(h_data.begin(), h_data.end(), d_data.begin()); return 0; } Thrust - Weld triangles ‣ Eliminate redundant vertices to form figure ‣ Procedure - Sort vertices - Collapse spans of like vertices - Search for each vertex’s unique index Thrust - Weld triangles ‣ Sort triangles: - Use sort with functor to sort respect to x and then to y ‣ Collapse spans of like vertices - Use unique: reorders array and points to the first repeated value #include ... const int N = 7; int A[N] = {1, 3, 3, 3, 2, 2, 1}; int *new_end = thrust::unique(A, A + N); // The first four values of A are now {1, 3, 2, 1} // Values beyond new_end are unspecified. \endcode ‣ Delete values beyond new iterator: vertices.erase()